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LiFePo battery?
- Thread starter RVjim
- Start date
I just caught up entire thread...whew!
My 7 is equipped with a Lightspeed electronic ignition system. I don't recall seeing any questions/answers regarding this...but I may have merely missed them.
Does anyone have experience with these batteries using electronic ignition?
I will be at the show in Anchorage in May (duh) and also at Oshkosh this year so I'm excited to be able to meet the EarthX Battery team.
BTW...I've been using these batteries in mi R/C planes for years (they're called A123 Batteries).
Thanks,
Bob
My 7 is equipped with a Lightspeed electronic ignition system. I don't recall seeing any questions/answers regarding this...but I may have merely missed them.
Does anyone have experience with these batteries using electronic ignition?
I will be at the show in Anchorage in May (duh) and also at Oshkosh this year so I'm excited to be able to meet the EarthX Battery team.
BTW...I've been using these batteries in mi R/C planes for years (they're called A123 Batteries).
Thanks,
Bob
jcaplins
Well Known Member
Be aware... (in laymans terms) that the BMS in the EarthX will basically shut the battery off in an under-volt or over-volt situation, and requires a special charger or, in a pinch, a high current "reset" to use it again.
This may or may not be an issue for whatever application you have, If you need to have electrons flowing from the alternator or battery to keep the engine running... Well, just be aware.
(disclosure: I have 2 for my project and I need the electrons to flow for the engine to stay running.)
grayforge
Well Known Member
Yep. I let one get too low and connected it in parallel to a motorcycle battery to get the LiPo charging using an old Lead Acid battery charger.
Since then, I purchased a dedicated LiPo charger from EarthX. They had a nice show special at OSH. It's $65 on their site right now. Not bad.
Since then, I purchased a dedicated LiPo charger from EarthX. They had a nice show special at OSH. It's $65 on their site right now. Not bad.
No personal experience yet but it seems to me that the Ah ratings of LiFePo batteries are not all that equivalent to what we have been accustomed to with lead acid batteries. With time, hopefully this knowledge will increase but for now I am going to assume that LiFePo do not have equivalent juice in them (despite the label that implies that they do) when used in our applications. So, my approach will be to use a LiFePo just big enough to start the engine reliably and depend on the B&C backup alternator to supply electrical endurance should the main alternator fail. Also using P-mags which are self powered once started so not quite the same as lightspeed. Also, it is imperative to have a low voltage warning system to let you know the instant when the main alternator fails and time to switch to the backup saving the battery for later. Some use automatic switching to the backup alternator, but it's still good to know what's going on so you can make wise decisions about the remainder of your flight.
Bevan
I don't have a backup alternator.
I have an ignition dedicated backup battery. This battery is also charged by the alternator.
BMS Over Discharge protection
Please let me explain the over discharge (under-volt) feature in the EarthX BMS and the over charge (over-volt) feature. In order for this feature to be activated, the battery must be drained to approximately 95-98% of it's capacity. It will disconnect at this point to save the battery from damage but there is also hardly any capacity left at this point either. A perfect example of when this happens, which is pretty often actually, is the pilot has left the master key on and comes back to his plane the next weekend. Any other battery would be discharged to the point of permanent damage and you are out the battery as well because they are not covered under warranty for this. The EarthX battery will open an electrical switch inside so it can not be drained lower and damage the cells. To reset it requires voltage and is a 3 second procedure if you have the right equipment with you. You need a charger (as the battery is drained and needs to be recharged), and you can have a jump pack or another battery you can connect it to in parallel. Or if you have the Optimate Lithium Charger TM-471, it is all automatic, just connect and let it recharge.
Now during flight, if your alternator has failed and you are flying on the capacity of the battery alone, as with any battery in this situation, you need to land before you run out of capacity. This is why it is so important to not undersize your battery and to understand the true capacity of the battery so you can safely land.
Now for the over charge (over volt situation). How our BMS works is if the internal voltage of the cells are higher than 15-16V, it will switch off and reset all on it's own when the voltage is decreased to a safe level. A couple of scenarios that can happen is if your alternator is charging your battery in this range, you have charging issues and if you have a faulty charger in this range, it can happen. If you continue to charge a lithium battery at this voltage, not only will you destroy it but you will cause extreme internal heat, which is not good either.
Hope that better explains how these features work!
Kathy
Please let me explain the over discharge (under-volt) feature in the EarthX BMS and the over charge (over-volt) feature. In order for this feature to be activated, the battery must be drained to approximately 95-98% of it's capacity. It will disconnect at this point to save the battery from damage but there is also hardly any capacity left at this point either. A perfect example of when this happens, which is pretty often actually, is the pilot has left the master key on and comes back to his plane the next weekend. Any other battery would be discharged to the point of permanent damage and you are out the battery as well because they are not covered under warranty for this. The EarthX battery will open an electrical switch inside so it can not be drained lower and damage the cells. To reset it requires voltage and is a 3 second procedure if you have the right equipment with you. You need a charger (as the battery is drained and needs to be recharged), and you can have a jump pack or another battery you can connect it to in parallel. Or if you have the Optimate Lithium Charger TM-471, it is all automatic, just connect and let it recharge.
Now during flight, if your alternator has failed and you are flying on the capacity of the battery alone, as with any battery in this situation, you need to land before you run out of capacity. This is why it is so important to not undersize your battery and to understand the true capacity of the battery so you can safely land.
Now for the over charge (over volt situation). How our BMS works is if the internal voltage of the cells are higher than 15-16V, it will switch off and reset all on it's own when the voltage is decreased to a safe level. A couple of scenarios that can happen is if your alternator is charging your battery in this range, you have charging issues and if you have a faulty charger in this range, it can happen. If you continue to charge a lithium battery at this voltage, not only will you destroy it but you will cause extreme internal heat, which is not good either.
Hope that better explains how these features work!
Kathy
Ah rating
Dear Bevan,
On some levels I will agree with you on this in that most lithium manufacturer do not list their true amp hour capacity (nor do the lead acid battery manufacturers) but instead give you an equivalent amp hour rating, which assumes it is in a functioning charging system and not being used as a main power source in the event of an alternator failing. We at EarthX list both as this is a very important piece of information you need in order to know how long you have battery power. As far as lead acid batteries go, Odyssey is one of the very few that actually list their capacity and depth of discharge that will deliver amps in the event of using the battery as a main power source. They publish you can use 80% of their listed Ah for this purpose. So as an example, the PC680 lists 16 Ah on their battery. In the event your alternator fails and you are on 100% battery power, you can access 80% of that amp hour or (16 * .80 = 12.8Ah of capacity). It is very difficult information to find on any lead acid manufacturers sites if at all, but the average accessible Ah is 30% which would mean if it is listed as 16 Ah, you can use (16 * .30 = 4.8 Ah).
Kathy
Dear Bevan,
On some levels I will agree with you on this in that most lithium manufacturer do not list their true amp hour capacity (nor do the lead acid battery manufacturers) but instead give you an equivalent amp hour rating, which assumes it is in a functioning charging system and not being used as a main power source in the event of an alternator failing. We at EarthX list both as this is a very important piece of information you need in order to know how long you have battery power. As far as lead acid batteries go, Odyssey is one of the very few that actually list their capacity and depth of discharge that will deliver amps in the event of using the battery as a main power source. They publish you can use 80% of their listed Ah for this purpose. So as an example, the PC680 lists 16 Ah on their battery. In the event your alternator fails and you are on 100% battery power, you can access 80% of that amp hour or (16 * .80 = 12.8Ah of capacity). It is very difficult information to find on any lead acid manufacturers sites if at all, but the average accessible Ah is 30% which would mean if it is listed as 16 Ah, you can use (16 * .30 = 4.8 Ah).
Kathy
jcaplins
Well Known Member
This is good news. The BMS is the reason I chose the EarthX batteries. I could not find any documentation stating the BMS will reset when the over-volt situation is corrected. (if it's there, I didn't see)
rv7charlie
Well Known Member
Hi Kathy,
I'm not sure that is a truly descriptive picture of lead/acid battery capacity. Most good mfgrs publish a set of discharge curves, depending on the actual discharge rate. A PC680, at 16 AH, will supply 1 amp for around 16 hours. If supplying 16 amps continuous, it *might* make 40 minutes to 'dead'.
When you talk about accessing 80% if capacity, I assume that you're talking about avoiding damage to the battery, right? I would contend that that figure isn't very useful in an a/c application, because the only time it would be significantly discharged would be after a charging system failure in flight, and in that case, you'd want to know the battery's endurance to completely flat, to the limit of overheat/fire danger.
So, what we really need to see is multiple discharge curves from 'full' to safely 'empty' at various discharge rates, as are shown in SLA (lead/acid) battery specs. See:
http://www.odysseybattery.com/documents/US-ODY-TM-002_1214.pdf
That way we can plug in the electrical load of our particular plane in battery-only operation, and determine the size battery we actually need. (Just about any lithium battery can supply enough short term power to crank an engine.)
Charlie
ChiefPilot
Well Known Member
I don't believe this is entirely accurate. The <non-EarthX brand> LiFePO4 battery I use has had this happen with no apparent ill effects i.e. same time to discharge state as before the incident. I wouldn't make a habit of it, but to say that any other battery would be discharged to the point of permanent damage is perhaps a bit of hyperbole given empirical evidence to the contrary.
BillL
Well Known Member
There is probably more detailed quantification needed on the over voltage behavior. Here is why. When the typical over voltage failure occurs, and if the plane is equipped with an over voltage protection, it will shut down the alternator. So lets suppose that the scenario is IFR, real weather, the VR fails high, the voltage goes up, the battery removes itself from the circuit (what happens?) then the voltage increases and at 16.9v, the crowbar involves and then the alternator is gone. Are we suddenly without alternator AND the battery? Maybe a little more understanding (testing) is needed to ensure . . . well, we can see the possibilities. It might be that the back up battery or back up alternator picks up, then the main battery returns in a few seconds and it is like any other emergency, but one needs to KNOW what behavior to plan and build a panel and system around.
I don't mean to be negative on the technology, but addressing the new failure modes seems prudent. If one is only flying VFR, then it is fine, the risk is much less.
Hi Kathy,
Thanks for monitoring this forum and for your reply.
I don't understand your "80%" number. When comparing Ah ratings (with Odyssey in this case) Oddysey's website claims their Ah rating is determined at a 10hr rate. That means a "100Ah battery can deliver 10 amps for 10 hours before the battery voltage drops to 1.67V per cell which happens to be 10 volts for a 12 volt battery." see...
http://www.odysseybattery.com/faq.aspx#7
Are you saying that the actual capacity (to 10 volts) is 80% of the above? Or are you saying that a typical "not new battery" could be said to have 80% capacity left?
Another question is...How long can the EarthX ETX36C battery provide 10 amps before the voltage drops to 10 Volts?
Also, your's and Oddysey's website claims a reserve capacity in minutes but doesn't state at what rate (of discharge). How can a reserve capacity be stated without any reference to a rate? Or, is it assumed to be at 10 amps?
Not trying to be critical, just trying to understand and make a fair comparison.
Bevan
Thanks for monitoring this forum and for your reply.
I don't understand your "80%" number. When comparing Ah ratings (with Odyssey in this case) Oddysey's website claims their Ah rating is determined at a 10hr rate. That means a "100Ah battery can deliver 10 amps for 10 hours before the battery voltage drops to 1.67V per cell which happens to be 10 volts for a 12 volt battery." see...
http://www.odysseybattery.com/faq.aspx#7
Are you saying that the actual capacity (to 10 volts) is 80% of the above? Or are you saying that a typical "not new battery" could be said to have 80% capacity left?
Another question is...How long can the EarthX ETX36C battery provide 10 amps before the voltage drops to 10 Volts?
Also, your's and Oddysey's website claims a reserve capacity in minutes but doesn't state at what rate (of discharge). How can a reserve capacity be stated without any reference to a rate? Or, is it assumed to be at 10 amps?
Not trying to be critical, just trying to understand and make a fair comparison.
Bevan
Bill Palmer
Well Known Member
Not the Theory of Everything
What my meager brain has learned so far about LiFePo4 batteries (. . . my humble attempt at some overall, but admittedly subjective, clarification based on internet data sources and my personal discussions with some manufacturer?s technical reps):
Battery Capacity:
Most LiFePo4 manufacturers specify their battery capacity in Equivalent Ampere Hours (EqAH). This ?equivalent? battery capacity is reverse-calculated from the LiFePo4?s superior cold cranking amps. The term ?equivalent? is very misleading. The ?lead acid? equivalent AH rating of a LiFePo4 battery is actually slightly less than 1/3 of the LiFePo4?s specified EqAH.
For example, the Odyssey PC680 battery has a 16AH ?lead acid? capacity. The EarthX ETX36C?s (36 EqAH) equivalent ?lead acid? capacity is actually between 11 and 12AH. Bottom Line: one EarthX ETX36C battery can out-crank a PC680, but the PC680 has the greater AH capacity (16AH versus approximately 11.5AH).
The good news: 2 EarthX ETX36C batteries total over 22AH in ?lead acid? capacity and weigh less than 7 pounds total compared to one PC680 with 16AH at 15.4 pounds. The very bad news: 2 EarthX ETX36C batteries cost well over $600, and one PC680 can be purchased for less than $100. You decide the winner!
Discharge Curve:
The LiFePo4 discharge curve is more like a step function (cliff). Everything is fine for quite awhile (for ?most? of the AH capacity . . . check the manufacturer?s data to define ?most?) and then the battery gives up very quickly. A lead acid discharge curve has more of a gradual downward slope with some degradation (volts) starting almost immediately. In other words, a lead acid battery gives up slowly, but degrades along the way. A LiFePo4 battery does not degrade much as it discharges, but it gives up more quickly (due to a lower AH rating).
In the case of an alternator failure, it is debatable (mainly subjective) regarding which battery is better. A LiFePo4 battery is good as long as you can shed load to stretch its AH capacity over time or have two LiFePo4 batteries for greater total AH capacity. If you cannot effectively shed load (for example, your IFR EFIS does not have its own backup power) or you do not have a redundant electrical power system, then the lead acid battery looks much better due to its higher AH capacity per battery. The best way to resolve this debate for yourself is to get each manufacturer?s discharge curves and compare them with your aircraft?s electrical system design to see which one is best; for you. Obviously, relative battery weight(s) and costs are big issues, too.
EarthX Battery Management System (BMS):
In the case of over-voltage or under-voltage (regulator or alternator failure), the EarthX?s BMS will shut down the battery?s LiFePo4 cells to protect them. Solution: Turn-off the alternator, and the EarthX battery will automatically reset and come back on-line. For LiFePo4 batteries without this internal BMS protection system (Ballistic or Shorai batteries, for example), the solution is still the same (turn-off the alternator), but some battery cell damage is probably inevitable for these batteries depending on how quickly the fault is detected and how quickly the alternator/regulator is turned off. What this potential cell damage might mean in terms of subsequent battery performance or safety seems to be mostly unknown. Is there anyone out there with actual failure experience or enough spare cash for destructive testing to give us an answer for these non-BMS LiFePo4 batteries?
Well, that?s all I have. I wish I had more time, energy, and good technical data (confident numbers) to further analyze LiFePo4 batteries, particularly in comparison to lead acid batteries, but I don?t. Who?s up next?!
I hope this overall ?clarification? post helps, anyway . . . use at your own risk!
What my meager brain has learned so far about LiFePo4 batteries (. . . my humble attempt at some overall, but admittedly subjective, clarification based on internet data sources and my personal discussions with some manufacturer?s technical reps):
Battery Capacity:
Most LiFePo4 manufacturers specify their battery capacity in Equivalent Ampere Hours (EqAH). This ?equivalent? battery capacity is reverse-calculated from the LiFePo4?s superior cold cranking amps. The term ?equivalent? is very misleading. The ?lead acid? equivalent AH rating of a LiFePo4 battery is actually slightly less than 1/3 of the LiFePo4?s specified EqAH.
For example, the Odyssey PC680 battery has a 16AH ?lead acid? capacity. The EarthX ETX36C?s (36 EqAH) equivalent ?lead acid? capacity is actually between 11 and 12AH. Bottom Line: one EarthX ETX36C battery can out-crank a PC680, but the PC680 has the greater AH capacity (16AH versus approximately 11.5AH).
The good news: 2 EarthX ETX36C batteries total over 22AH in ?lead acid? capacity and weigh less than 7 pounds total compared to one PC680 with 16AH at 15.4 pounds. The very bad news: 2 EarthX ETX36C batteries cost well over $600, and one PC680 can be purchased for less than $100. You decide the winner!
Discharge Curve:
The LiFePo4 discharge curve is more like a step function (cliff). Everything is fine for quite awhile (for ?most? of the AH capacity . . . check the manufacturer?s data to define ?most?) and then the battery gives up very quickly. A lead acid discharge curve has more of a gradual downward slope with some degradation (volts) starting almost immediately. In other words, a lead acid battery gives up slowly, but degrades along the way. A LiFePo4 battery does not degrade much as it discharges, but it gives up more quickly (due to a lower AH rating).
In the case of an alternator failure, it is debatable (mainly subjective) regarding which battery is better. A LiFePo4 battery is good as long as you can shed load to stretch its AH capacity over time or have two LiFePo4 batteries for greater total AH capacity. If you cannot effectively shed load (for example, your IFR EFIS does not have its own backup power) or you do not have a redundant electrical power system, then the lead acid battery looks much better due to its higher AH capacity per battery. The best way to resolve this debate for yourself is to get each manufacturer?s discharge curves and compare them with your aircraft?s electrical system design to see which one is best; for you. Obviously, relative battery weight(s) and costs are big issues, too.
EarthX Battery Management System (BMS):
In the case of over-voltage or under-voltage (regulator or alternator failure), the EarthX?s BMS will shut down the battery?s LiFePo4 cells to protect them. Solution: Turn-off the alternator, and the EarthX battery will automatically reset and come back on-line. For LiFePo4 batteries without this internal BMS protection system (Ballistic or Shorai batteries, for example), the solution is still the same (turn-off the alternator), but some battery cell damage is probably inevitable for these batteries depending on how quickly the fault is detected and how quickly the alternator/regulator is turned off. What this potential cell damage might mean in terms of subsequent battery performance or safety seems to be mostly unknown. Is there anyone out there with actual failure experience or enough spare cash for destructive testing to give us an answer for these non-BMS LiFePo4 batteries?
Well, that?s all I have. I wish I had more time, energy, and good technical data (confident numbers) to further analyze LiFePo4 batteries, particularly in comparison to lead acid batteries, but I don?t. Who?s up next?!
I hope this overall ?clarification? post helps, anyway . . . use at your own risk!
grayforge
Well Known Member
Nice Summary!
Another option, besides 2 x ETX36C's would be 2 x ETX24C's. This would provide about a 16AH equivalent power source. Same as the PC680 at just over 5lbs for just over $500.
Interesting that the single ETX48E is well over twice the price of two 24's.
Russ
Another option, besides 2 x ETX36C's would be 2 x ETX24C's. This would provide about a 16AH equivalent power source. Same as the PC680 at just over 5lbs for just over $500.
Interesting that the single ETX48E is well over twice the price of two 24's.
Russ
Bill Palmer
Well Known Member
Not Battery Therapy
I lied . . . (?that?s all I have?). I do have some more Lucy ?5 Cents? Psychiatric Battery Counseling (it?s worth what you?re paying for it!):
Electrical Storage Technology:
A LiFePo4 battery is a dry, electronic system. It?s more like a big, long-acting capacitor and regulator than anything else. It?s definitely NOT your dad?s wet, electrochemical, lead-acid battery. LiFePo4 is silicon-like technology; not chemical (lead acid) technology. LiFePo4 and Lead Acid represent completely different physics. Assumptions and experience with one cannot generally be applied to the other. In other words, if you?re going LiFePo4, throw out everything you ever learned about lead acid batteries, because your experience is no longer applicable and could even be dangerous. If you decide to go LiFePo4, you MUST LEARN LiFePo4. Forget lead acid. Don?t use lead acid chargers, don?t install or treat a LiFePo4 battery like a lead acid battery; don?t even think about going there!
LiFePo4 Installation:
A LiFePo4 battery is a piece of electronics. Firewall forward (heat and vibration) is an issue for electronics. You might think about adding vibration protection, insulation, and cooling if you are planning to install a LiFePo4 battery firewall forward. In my opinion, you cannot blindly insert a LiFePo4 battery in the same location as a typically more durable and environmentally-tolerant lead-acid battery. Although LiFePo4 batteries are designed for relatively harsh operational environments as installed in motorcycles and ATVs, there is probably some airflow to the battery locations in those vehicles, and those vehicles may have much less continuous, strong vibration than your RV with its thunder-thumping Lycoming. Until there is more experience with LiFePo4 batteries operating in harsh environments, you might want to consider installing a LiFePo4 battery behind the firewall as is recommended for external regulators and similar electronics. You might even consider shock-mounting the LiFePo4 battery. Electronics can be delicate, you know!
Now where?s Charlie Brown? I?m going to swap that football for a LiFePo4 battery!
I lied . . . (?that?s all I have?). I do have some more Lucy ?5 Cents? Psychiatric Battery Counseling (it?s worth what you?re paying for it!):
Electrical Storage Technology:
A LiFePo4 battery is a dry, electronic system. It?s more like a big, long-acting capacitor and regulator than anything else. It?s definitely NOT your dad?s wet, electrochemical, lead-acid battery. LiFePo4 is silicon-like technology; not chemical (lead acid) technology. LiFePo4 and Lead Acid represent completely different physics. Assumptions and experience with one cannot generally be applied to the other. In other words, if you?re going LiFePo4, throw out everything you ever learned about lead acid batteries, because your experience is no longer applicable and could even be dangerous. If you decide to go LiFePo4, you MUST LEARN LiFePo4. Forget lead acid. Don?t use lead acid chargers, don?t install or treat a LiFePo4 battery like a lead acid battery; don?t even think about going there!
LiFePo4 Installation:
A LiFePo4 battery is a piece of electronics. Firewall forward (heat and vibration) is an issue for electronics. You might think about adding vibration protection, insulation, and cooling if you are planning to install a LiFePo4 battery firewall forward. In my opinion, you cannot blindly insert a LiFePo4 battery in the same location as a typically more durable and environmentally-tolerant lead-acid battery. Although LiFePo4 batteries are designed for relatively harsh operational environments as installed in motorcycles and ATVs, there is probably some airflow to the battery locations in those vehicles, and those vehicles may have much less continuous, strong vibration than your RV with its thunder-thumping Lycoming. Until there is more experience with LiFePo4 batteries operating in harsh environments, you might want to consider installing a LiFePo4 battery behind the firewall as is recommended for external regulators and similar electronics. You might even consider shock-mounting the LiFePo4 battery. Electronics can be delicate, you know!
Now where?s Charlie Brown? I?m going to swap that football for a LiFePo4 battery!
Try and explain it with graphs
I am attempting to copy curves from our manuals and from the Odyssey manuals for ease of reference. Every manufacturer rated Ah is confusing. So what we always recommend is to look at the discharge curves. Here is a comparison of the Odyssey PC 680 and EarthX ETX36.
First, notice the curves are not exactly the same format. The Odyssey curve is Amp on Y axis and hours on X axis, with volts decreasing to 10V, while the EarthX curve is volts on Y axis and Ah on X axis (hours = Ah/Amps).
For airplane applications, a 12 amp discharge rate is common, so below is an example that compares the Odyssey PC680 and EarthX ETX36 discharge at 12 amps.
12amp Discharge Rate Example:
Per the Odyssey discharge table (below to right), line 8, a discharge rate of 12.3amps will drain the battery to 10V within 1 hour, consuming 12.3Ah.
Per the EarthX discharge table (below), lime green line, a discharge rate of 12amps (1C for 12Ah battery is 12amp) will drain the battery to 10.4V within 1 hour (hours = Ah/Amp, 12Ah/12Amp= 1hour), consuming 12.0Ah.
So as you can see from this example, the EarthX?s ETX36 is equivalent to the Odyssey PC680 in discharge Ah capacity.
Note with an EarthX lithium battery, the discharge rate has little effect on the discharge Ah capacity, for the curves for .1C , .5C and 1C are almost identical, meaning the Ah capacity for 1.2amp, 6amp and 12amp discharge rate are almost identical.
Reserve capacity (minutes): reserve capacity is the simply the discharge curve for a 20A discharge rate. So for the EarthX battery it is 12Ah (12Ah/20amp = .6 hour = 36minutes). For the Odessy, per the chart above (line 6), it is approximately 30minutes.
Kathy
I am attempting to copy curves from our manuals and from the Odyssey manuals for ease of reference. Every manufacturer rated Ah is confusing. So what we always recommend is to look at the discharge curves. Here is a comparison of the Odyssey PC 680 and EarthX ETX36.
First, notice the curves are not exactly the same format. The Odyssey curve is Amp on Y axis and hours on X axis, with volts decreasing to 10V, while the EarthX curve is volts on Y axis and Ah on X axis (hours = Ah/Amps).
For airplane applications, a 12 amp discharge rate is common, so below is an example that compares the Odyssey PC680 and EarthX ETX36 discharge at 12 amps.
12amp Discharge Rate Example:
Per the Odyssey discharge table (below to right), line 8, a discharge rate of 12.3amps will drain the battery to 10V within 1 hour, consuming 12.3Ah.
Per the EarthX discharge table (below), lime green line, a discharge rate of 12amps (1C for 12Ah battery is 12amp) will drain the battery to 10.4V within 1 hour (hours = Ah/Amp, 12Ah/12Amp= 1hour), consuming 12.0Ah.
So as you can see from this example, the EarthX?s ETX36 is equivalent to the Odyssey PC680 in discharge Ah capacity.
Note with an EarthX lithium battery, the discharge rate has little effect on the discharge Ah capacity, for the curves for .1C , .5C and 1C are almost identical, meaning the Ah capacity for 1.2amp, 6amp and 12amp discharge rate are almost identical.
Reserve capacity (minutes): reserve capacity is the simply the discharge curve for a 20A discharge rate. So for the EarthX battery it is 12Ah (12Ah/20amp = .6 hour = 36minutes). For the Odessy, per the chart above (line 6), it is approximately 30minutes.
Kathy
Bill Palmer
Well Known Member
Actual AH
Thanks, Kathy
Okay, you are saying that the Odyssey and EarthX discharge curves show that the actual, equivalent AH rating of the PC680 and ETX36 are nearly identical at around 12AH. (In other words, a 20-amp load will discharge either battery in about 30 minutes plus a little.) Is that correct?
If so, I stand corrected. The PC680 does not have greater AH capacity. I learn something new every day, but only when I shoot my mouth off, forget my own rules, don't finish my homework, and embarrass myself!
Also, if so, why does Odyssey generally spec the PC680 at 16AH and EarthX the ETX36C at 36EqAH?
Thanks, Kathy
Okay, you are saying that the Odyssey and EarthX discharge curves show that the actual, equivalent AH rating of the PC680 and ETX36 are nearly identical at around 12AH. (In other words, a 20-amp load will discharge either battery in about 30 minutes plus a little.) Is that correct?
If so, I stand corrected. The PC680 does not have greater AH capacity. I learn something new every day, but only when I shoot my mouth off, forget my own rules, don't finish my homework, and embarrass myself!
Also, if so, why does Odyssey generally spec the PC680 at 16AH and EarthX the ETX36C at 36EqAH?
rv7charlie
Well Known Member
Sorry, Kathy, but if the graph is labeled correctly, it isn't an equivalent curve (there's no time axis).
Bill Palmer
Well Known Member
Apples and Apples
Kathy,
In other words, I believe Charlie would like to see the ETX36 capacity data under the same conditions and in exactly same format, including discharge time, as the PC680 discharge curve and table. Only in this way can we finally obtain a one-to-one (“equivalent”) comparison with no assumptions, calculations, or “if so” required. Can you provide that? I think we would all appreciate seeing that.
Thanks,
Kathy,
In other words, I believe Charlie would like to see the ETX36 capacity data under the same conditions and in exactly same format, including discharge time, as the PC680 discharge curve and table. Only in this way can we finally obtain a one-to-one (“equivalent”) comparison with no assumptions, calculations, or “if so” required. Can you provide that? I think we would all appreciate seeing that.
Thanks,
Last edited:
I do understand the entire comparison of batteries, be it lead acid or lithium, can be very daunting and confusing. I am going to try to simplify.
In the aircraft world, your battery has 2 functions, starting your engine and back up power if your alternator fails. The CCA rating of the battery is used to make sure the battery has enough cranking power to do it. The usable amperage the battery has is the amount of amperage you will have to run your plane in the event your alternator fails and you are running the aircraft on battery power alone.
Why and how different manufacturers rate and advertise their spec's can be a mystery and I am not an expert nor an investigator for the other thousands of battery manufacturers out there. I recommend you contact whichever battery manufacturer you want information from directly and get the information straight from them.
So here it is straight from EarthX. Our ETX36 series has 12Ah that are usable and has 405CCA that is designed for a 60 amp or smaller alternator. If your alternator fails and you are using the battery to power your plane:
You use 6 amps per hour you have 2 hours to land your plane.
You use 12 amps per hour, you have 1 hour to land your plane.
You use 24 amps in an hour, you have 30 minutes to land your plane.
Our ETX48 has 24Ah usable amp hours and has 600CCA that is designed for a 120 amp or smaller alternator. If your alternator fails and you are using the battery to power your plane:
You use 6 amps per hour you have 4 hours to land your plane.
You use 12 amps per hour, you have 2 hour to land your plane.
You use 24 amps in an hour, you have 1 hour to land your plane.
As a builder and pilot, you need to know how much amperage you need in the event you are flying without an alternator. Personally, if I was in a plane and my alternator failed, I would be immediately looking for the nearest place to land, but that is my comfort zone. I don't like driving my car when the gage is near "E" either.
Hope that simplified things as far as the EarthX battery goes.
Kathy
In the aircraft world, your battery has 2 functions, starting your engine and back up power if your alternator fails. The CCA rating of the battery is used to make sure the battery has enough cranking power to do it. The usable amperage the battery has is the amount of amperage you will have to run your plane in the event your alternator fails and you are running the aircraft on battery power alone.
Why and how different manufacturers rate and advertise their spec's can be a mystery and I am not an expert nor an investigator for the other thousands of battery manufacturers out there. I recommend you contact whichever battery manufacturer you want information from directly and get the information straight from them.
So here it is straight from EarthX. Our ETX36 series has 12Ah that are usable and has 405CCA that is designed for a 60 amp or smaller alternator. If your alternator fails and you are using the battery to power your plane:
You use 6 amps per hour you have 2 hours to land your plane.
You use 12 amps per hour, you have 1 hour to land your plane.
You use 24 amps in an hour, you have 30 minutes to land your plane.
Our ETX48 has 24Ah usable amp hours and has 600CCA that is designed for a 120 amp or smaller alternator. If your alternator fails and you are using the battery to power your plane:
You use 6 amps per hour you have 4 hours to land your plane.
You use 12 amps per hour, you have 2 hour to land your plane.
You use 24 amps in an hour, you have 1 hour to land your plane.
As a builder and pilot, you need to know how much amperage you need in the event you are flying without an alternator. Personally, if I was in a plane and my alternator failed, I would be immediately looking for the nearest place to land, but that is my comfort zone. I don't like driving my car when the gage is near "E" either.
Hope that simplified things as far as the EarthX battery goes.
Kathy
Kathy,
Thanks for the clear explanation. I note your ratings at 25 deg C. Do you have data for the AH capacity at reduced temps, like we often operate in? Something like -10 deg C and 0 deg C. That would be useful also given the loss of capacity of Lion batteries at low temps.
Thanks for the clear explanation. I note your ratings at 25 deg C. Do you have data for the AH capacity at reduced temps, like we often operate in? Something like -10 deg C and 0 deg C. That would be useful also given the loss of capacity of Lion batteries at low temps.
BillL
Well Known Member
But they Do!
Comparison of different battery chemistries is not easy. When Kathy said "C" rate, that is the one hour amperage. For the Blah Blah 36, that is 12 amps.
All must look closer at the data. The AGM-PbA battery - 680, at the 1.5C "rate" or at 12*1.5=18 amps will have a LOWER AMP HOUR RATING. That non-linearity makes this data-at-a-point so thorny. So as the amp draw goes up on the 680 the amp-hour capacity goes DOWN. Internal resistance bites.
If you can live on less than 12amps use the 680, but if you might use more than 12 amps - the EarthX is better.
Both charts have the same conditions, but different presentation of it.
This Ah vs C-rate is extremely important to hybrid cars and where the Li and NiMH based chemistries really shine. Note that the EarthX has a constant Ah capability at several C rates. Now . . . it is not so good (compared to the 680) at low amp discharge rates, but look at the higher ones, you (we) can still use all of the 12 amp-hour rating!! Unlike the PbA battery.
Nice data, Kathy, thanks!!
Comparison of different battery chemistries is not easy. When Kathy said "C" rate, that is the one hour amperage. For the Blah Blah 36, that is 12 amps.
All must look closer at the data. The AGM-PbA battery - 680, at the 1.5C "rate" or at 12*1.5=18 amps will have a LOWER AMP HOUR RATING. That non-linearity makes this data-at-a-point so thorny. So as the amp draw goes up on the 680 the amp-hour capacity goes DOWN. Internal resistance bites.
If you can live on less than 12amps use the 680, but if you might use more than 12 amps - the EarthX is better.
Both charts have the same conditions, but different presentation of it.
This Ah vs C-rate is extremely important to hybrid cars and where the Li and NiMH based chemistries really shine. Note that the EarthX has a constant Ah capability at several C rates. Now . . . it is not so good (compared to the 680) at low amp discharge rates, but look at the higher ones, you (we) can still use all of the 12 amp-hour rating!! Unlike the PbA battery.
Nice data, Kathy, thanks!!
Bill Palmer
Well Known Member
I Can See Clearly Now
Thanks, Kathy and Bill . . . Some clarity at last!
An answer to Dan?s question about environmental temperature would be plus!
Thanks, Kathy and Bill . . . Some clarity at last!
An answer to Dan?s question about environmental temperature would be plus!
Data at reduced temperatures for AH
I have the data from our engineering department and the answer to this question is:
At 25 deg C = 12ah
At 0 deg C (.95 * 12ah = 11.4ah)
At -17 deg C (.9 *12ah=10.8ah)
Kathy
I have the data from our engineering department and the answer to this question is:
At 25 deg C = 12ah
At 0 deg C (.95 * 12ah = 11.4ah)
At -17 deg C (.9 *12ah=10.8ah)
Kathy
Mandatory Alert Service Bulletin from Rotax
One of our aircraft manufacturers sent this alert to us today and thought it was important information to pass on. It was a mandatory alert sent out on May 29, 2015 by Rotax concerning the use of lithium batteries in aircraft.
What I found exciting and interesting is they actually copied verbatim from our spec's and website the features the BMS must have to be approved.
Here is a copy of the alert:
NEW RELEASE
MANDATORY
ROTAX 912i (series)
ALERT SERVICE BULLETIN:
"The use of lithium-ion batteries in combination with the ROTAX Engine Type 912 i Series"
ASB-912 i-005iS
ROTAX 912iS & 912iS Sport aircraft engines are approved for operation with lithium-ion batteries if the aircraft has been equipped with a suitable battery management system (qualified by the aircraft manufacturer).
This requirement has been specified in the 912 i (series) installation manuals since Edition 1 Revision 2. The purpose of this bulletin is to bring this to the attention of users of engines delivered with earlier (Rev.0 or Rev.1) versions of the installation manual.
This is a MANDATORY alert service bulletin, and users of lithium-ion batteries should verify that their battery includes a suitable battery management system BEFORE THE NEXT FLIGHT.
WHY USE A BATTERY MANAGEMENT SYSTEM?
Lithium batteries are fundamentally different than lead-acid batteries. If overheated or overcharged, Li-Ion cells are prone to accelerated cell degradation and can catch fire or even explode. The lithium cells inside the battery need electronics to monitor and balance the voltage & charge level of the individual cells.
Some older types of lithium batteries require an external balancing charger, which you have to plug in periodically to ?top off? and balance the cells. These kinds of batteries are NOT approved.
The more modern lithium batteries have a built-in microprocessor Battery Management System (BMS) that continuously monitors the charge level of each cell and balances the charge when needed, protecting the cells from overcharge or over-discharge. Some can also provide short circuit protection, and excessive cranking protection.
Typically, the individual cells in a battery have somewhat different capacities and may be at different levels of state of charge (SOC). Without balancing, the cell of smallest capacity is a "weak point", it can be easily overcharged or over-discharged while cells with higher capacity undergo only partial cycle. For the higher capacity cells to undergo full charge/discharge cycle of the largest amplitude, balancer should ?protect? the weaker cells; so that in a balanced battery, the cell with the largest capacity can be filled without overcharging any other (i. e. weaker, smaller) cell, and it can be emptied without over-discharging any other cell. Battery balancing is done by transferring energy from or to individual cells, until the SOC of the cell with the lowest capacity is equal to the battery's SOC.
A full battery management system (BMS) might include active balancing as well as temperature monitoring, charging, and other features to maximize the life of the battery pack.
Bottom line: if you use a lithium battery in your aircraft, make sure it includes a built-in Battery Management System.
Here is the link to the actual alert: http://legacy.rotaxowner.com/si_tb_info/alertbulletins/asb-912i-005is.pdf
Kathy
One of our aircraft manufacturers sent this alert to us today and thought it was important information to pass on. It was a mandatory alert sent out on May 29, 2015 by Rotax concerning the use of lithium batteries in aircraft.
What I found exciting and interesting is they actually copied verbatim from our spec's and website the features the BMS must have to be approved.
Here is a copy of the alert:
NEW RELEASE
MANDATORY
ROTAX 912i (series)
ALERT SERVICE BULLETIN:
"The use of lithium-ion batteries in combination with the ROTAX Engine Type 912 i Series"
ASB-912 i-005iS
ROTAX 912iS & 912iS Sport aircraft engines are approved for operation with lithium-ion batteries if the aircraft has been equipped with a suitable battery management system (qualified by the aircraft manufacturer).
This requirement has been specified in the 912 i (series) installation manuals since Edition 1 Revision 2. The purpose of this bulletin is to bring this to the attention of users of engines delivered with earlier (Rev.0 or Rev.1) versions of the installation manual.
This is a MANDATORY alert service bulletin, and users of lithium-ion batteries should verify that their battery includes a suitable battery management system BEFORE THE NEXT FLIGHT.
WHY USE A BATTERY MANAGEMENT SYSTEM?
Lithium batteries are fundamentally different than lead-acid batteries. If overheated or overcharged, Li-Ion cells are prone to accelerated cell degradation and can catch fire or even explode. The lithium cells inside the battery need electronics to monitor and balance the voltage & charge level of the individual cells.
Some older types of lithium batteries require an external balancing charger, which you have to plug in periodically to ?top off? and balance the cells. These kinds of batteries are NOT approved.
The more modern lithium batteries have a built-in microprocessor Battery Management System (BMS) that continuously monitors the charge level of each cell and balances the charge when needed, protecting the cells from overcharge or over-discharge. Some can also provide short circuit protection, and excessive cranking protection.
Typically, the individual cells in a battery have somewhat different capacities and may be at different levels of state of charge (SOC). Without balancing, the cell of smallest capacity is a "weak point", it can be easily overcharged or over-discharged while cells with higher capacity undergo only partial cycle. For the higher capacity cells to undergo full charge/discharge cycle of the largest amplitude, balancer should ?protect? the weaker cells; so that in a balanced battery, the cell with the largest capacity can be filled without overcharging any other (i. e. weaker, smaller) cell, and it can be emptied without over-discharging any other cell. Battery balancing is done by transferring energy from or to individual cells, until the SOC of the cell with the lowest capacity is equal to the battery's SOC.
A full battery management system (BMS) might include active balancing as well as temperature monitoring, charging, and other features to maximize the life of the battery pack.
Bottom line: if you use a lithium battery in your aircraft, make sure it includes a built-in Battery Management System.
Here is the link to the actual alert: http://legacy.rotaxowner.com/si_tb_info/alertbulletins/asb-912i-005is.pdf
Kathy
NEW AIRCRAFT MODELS ARE ON THE WEBSITE!
As promised to the Van's forum readers, you are the first to know that the new aircraft lithium batteries are now available for pre-order on the website and they are scheduled to ship at the end of July 17th week.
All of our batteries meet the criteria set forth by Rotax to be an approved lithium battery, (and we are the only lithium battery on the market to have this approval), but what these 3 new models bring (ETX680, ETX900, ETX1200) in addition to what the other models have is:
1. Redundant electronics for the BMS board
2. LED battery fault light indicator that can also be plugged into your control panel.
3. A higher cranking, more capacity models (ETX900, ETX1200) if you need or want more.
These new models (ETX680, ETX900) will fit into preexisting PC680 battery box hardware and we are also going to have an aluminum battery box for sale as well on the site that is rated for 30 G Force, and 7 ounces of weight. That isn't on the site yet, but by end of tomorrow it should be there. Check it out at www.earthxmotorsports.com
Thanks Van's for all your support!
Kathy
As promised to the Van's forum readers, you are the first to know that the new aircraft lithium batteries are now available for pre-order on the website and they are scheduled to ship at the end of July 17th week.
All of our batteries meet the criteria set forth by Rotax to be an approved lithium battery, (and we are the only lithium battery on the market to have this approval), but what these 3 new models bring (ETX680, ETX900, ETX1200) in addition to what the other models have is:
1. Redundant electronics for the BMS board
2. LED battery fault light indicator that can also be plugged into your control panel.
3. A higher cranking, more capacity models (ETX900, ETX1200) if you need or want more.
These new models (ETX680, ETX900) will fit into preexisting PC680 battery box hardware and we are also going to have an aluminum battery box for sale as well on the site that is rated for 30 G Force, and 7 ounces of weight. That isn't on the site yet, but by end of tomorrow it should be there. Check it out at www.earthxmotorsports.com
Thanks Van's for all your support!
Kathy
Last edited:
[email protected]
Well Known Member
Barely fits... sorta
Heads up... The new 'PC680' form factor is NOT a drop in fit.
I was able to rock it back and forth and force it down but it does not bottom out... hope I can get it back out
Might be able to trim the plastic case a bit though.
The status indicator faces the firewall.
The contact lugs are centerline and a new hold down strap will need to be fabricated.
It is a wee bit too fat and an inch or so less wide.
Disappointed in the fit.
updated after flight home from Oshkosh:
http://www.vansairforce.com/community/showthread.php?p=1000565#post1000565
Heads up... The new 'PC680' form factor is NOT a drop in fit.
I was able to rock it back and forth and force it down but it does not bottom out... hope I can get it back out
Might be able to trim the plastic case a bit though.
The status indicator faces the firewall.
The contact lugs are centerline and a new hold down strap will need to be fabricated.
It is a wee bit too fat and an inch or so less wide.
Disappointed in the fit.
updated after flight home from Oshkosh:
http://www.vansairforce.com/community/showthread.php?p=1000565#post1000565
Last edited:
Raymo
Well Known Member
Heads up... The new 'PC680' form factor is NOT a drop in fit.
I was able to rock it back and forth and force it down but it does not bottom out... hope I can get it back out
Might be able to trim the plastic case a bit though.
The status indicator faces the firewall.
The contact lugs are centerline and a new hold down strap will need to be fabricated.
It is a wee bit too fat and an inch or so less wide.
Disappointed in the fit.
Which model did you purchase? ETX680, ETX900 or ETX1200?
[email protected]
Well Known Member
All three are in the same form factor
All three sizes are in the same exterior form factor...
All three sizes are in the same exterior form factor...
Hi Kathy,
Can you please clarify the statement below, as it is not true;
"These new models will fit into any preexisting PC680 battery box hardware"
I hope that there is a solution to this issue ?
Can you please clarify the statement below, as it is not true;
"These new models will fit into any preexisting PC680 battery box hardware"
I hope that there is a solution to this issue ?
ETX680 fitment
Dear Stephen,
First off, it was a pleasure to meet you in person at the show and I enjoyed meeting you. I am very sad to hear you say you are disappointed in the fitment of the new ETX680. The measurements of the PC680 is: 7.2 x 3.1 x 6.6 and the new ETX680 measurements is: 6.5 x 3.1 x 6.6. There is foam spacers provided that addresses the difference in length of .7 inches in length which should take about 5 seconds to modify.
We have purchased and tried multiple battery boxes provided for the PC680 and fitment was no issue that we discovered. As there are multiple aftermarket suppliers, I am not sure which one you have nor why you had issues getting the fitment to work. I do apologize for your frustrations and based on the size of the batteries, the PC680 and the ETX680, I am not sure why you had difficulty with the fitment.
Kathy
Heads up... The new 'PC680' form factor is NOT a drop in fit.
I was able to rock it back and forth and force it down but it does not bottom out... hope I can get it back out
Might be able to trim the plastic case a bit though.
The status indicator faces the firewall.
The contact lugs are centerline and a new hold down strap will need to be fabricated.
It is a wee bit too fat and an inch or so less wide.
Disappointed in the fit.
Dear Stephen,
First off, it was a pleasure to meet you in person at the show and I enjoyed meeting you. I am very sad to hear you say you are disappointed in the fitment of the new ETX680. The measurements of the PC680 is: 7.2 x 3.1 x 6.6 and the new ETX680 measurements is: 6.5 x 3.1 x 6.6. There is foam spacers provided that addresses the difference in length of .7 inches in length which should take about 5 seconds to modify.
We have purchased and tried multiple battery boxes provided for the PC680 and fitment was no issue that we discovered. As there are multiple aftermarket suppliers, I am not sure which one you have nor why you had issues getting the fitment to work. I do apologize for your frustrations and based on the size of the batteries, the PC680 and the ETX680, I am not sure why you had difficulty with the fitment.
Kathy
Odyssey dimensions from their website are 7.15 x 3.00 x 6.65
The odyssey battery fits the battery case supplied by Vans exactly.
The width specified for your battery is 3.1 inches and this does not work.
This is probably the case for most Vans supplied battery cases.
Cheers
The odyssey battery fits the battery case supplied by Vans exactly.
The width specified for your battery is 3.1 inches and this does not work.
This is probably the case for most Vans supplied battery cases.
Cheers
Raymo
Well Known Member
I looked at their website and it said the 1200 was slightly larger than the others. Thus the question on which you purchased.
JohnInReno
Well Known Member
ETX900 installation
I recently installed an ETX900 in my RV9A. As reported by others, it is not EXACTLY a "Drop-In" replacement for the PC680 mounted on the firewall. Adding a couple of washers or shims would solve the depth issue. That still left the hold-down to fabricate because their lugs are in the center.
I elected to use their "universal" box instead. It matches the firewall mounting pattern on the PC680 box and has a front mounted hold-down.
I am satisfied with the installation and it spins the prop like crazy! Others have noted that the EarthX batteries will accept all the amperage your alternator will generate. On my first start, I started the engine with the alternator off to see if it would activate the low voltage light. When I enabled the alternator I saw the amp meter hit 64 amps. Not bad for an alternator rated at 60 amps. The amps started coming down after 15-20 seconds and reached the normal 17 amps in due time. I do not know what the effect 64 amps would have on an ETX680 which is rated for 60 amps. The ETX900 is rated for an 80 amp alternator so I am in spec.
I recently installed an ETX900 in my RV9A. As reported by others, it is not EXACTLY a "Drop-In" replacement for the PC680 mounted on the firewall. Adding a couple of washers or shims would solve the depth issue. That still left the hold-down to fabricate because their lugs are in the center.
I elected to use their "universal" box instead. It matches the firewall mounting pattern on the PC680 box and has a front mounted hold-down.
I am satisfied with the installation and it spins the prop like crazy! Others have noted that the EarthX batteries will accept all the amperage your alternator will generate. On my first start, I started the engine with the alternator off to see if it would activate the low voltage light. When I enabled the alternator I saw the amp meter hit 64 amps. Not bad for an alternator rated at 60 amps. The amps started coming down after 15-20 seconds and reached the normal 17 amps in due time. I do not know what the effect 64 amps would have on an ETX680 which is rated for 60 amps. The ETX900 is rated for an 80 amp alternator so I am in spec.
