LiFePo battery?

[grayforge]

Oh, and welcome to VAF!

[rjbob]

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

[jcaplins]

Originally Posted by grayforge

The EarthX batteries have a built-in BMS.

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]

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.

[Bevan]

Originally Posted by rjbob

Does anyone have experience with these batteries using electronic ignition?

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

[rjbob]

Originally Posted by Bevan

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.

[EarthX Lithium]

Originally Posted by jcaplins

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.)

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

[EarthX Lithium]

Originally Posted by Bevan

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

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]

Originally Posted by EarthX Lithium

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

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]

Originally Posted by EarthX Lithium

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

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/docume...M-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