The EarthX batteries have a built-in BMS.
Does anyone have experience with these batteries using electronic ignition?
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
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.)
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
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
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
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.
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
Sorry, Kathy, but if the graph is labeled correctly, it isn't an equivalent curve (there's no time axis).
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.
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.
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 will fit into any 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
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.
All three sizes are in the same exterior form factor...