ETLB Squawk Forums — Archive

Whats the deal with lithium batteries, supposedly 1/3 the weight of a lead acid battery but from what I have read the battery needs a special charger if it has been deep discharged. From what I have read the lithium iron batteries are the most user friendly.

I have an EarthX lithium iron phosphate (LiFePO4) for my Rotax 503 starter.  It charges correctly using the 503's built in alternator and a Key West regulator/rectifier.  EarthX batteries have a built in battery management system that lets them work with any normal charger that provides between 13.5 and 14.6 volts.  The weight of a lithium battery is 70% less than a lead acid battery (about 1/6 the weight).  The only downside to lithium is that they are very expensive.

https://earthxbatteries.com/our-batteries/lithium-battery-technology

Thanks rad, anytime you say the word aviation, there is a loud cha Ching sound. I found a lithium iron battery for $55. 6 ah batt that weighs 1 pound.

DO NOT UNDER ANY CIRCUMSTANCES DO THIS WITH THE STANDARD ROTAX REGULATOR. Within an hour, the battery destroyed itself and the electrical system in my Max. The battery, fitted under my seat melted and failed before it caught fire, fortunately. I have gone back to a sealed lead acid.

For what it is worth, I have had truly excellent value from a Ballistic EVO2 battery with a Limbach engine.

Quoted from tomshep DO NOT UNDER ANY CIRCUMSTANCES DO THIS WITH THE STANDARD ROTAX REGULATOR. Within an hour, the battery destroyed itself and the electrical system in my Max. The battery, fitted under my seat melted and failed before it caught fire, fortunately. I have gone back to a sealed lead acid.

You must not use a plain lithium iron or lithium iron phosphate battery with a normal charging system.  They require a special battery management system to both charge the cells to the proper voltage and to balance the cells so that all have the same voltage.  Overcharging a lithium iron battery leads to overheating and melt down.  Luckily, lithium iron batteries don't often explode and catch fire like lithium polymer (cell phone battery!) ones.

The EarthX batteries have a BMS built into the battery case and are safe to use with a charging system providing 13.5 to 14.6 volts.  Mine works with a Rotax 503 and a Key West regulator/rectifier.  

i run a aerovoltz Li-fe and a key west regulator with no problems. i did purchase the special charger to balance the cells once a month but the regulator maintains the voltage.

monte p  

I suspect most of the problems come from when the voltage is ran way down, and that is when you need a "special charger". I appears earthx batteries do have circuitry built in for any charging system including typical lead acid chargers.

If your LiFePo battery has a built in charge controller you can use almost any 12 volt charging system EXCEPT those that put out a periodic voltage spike to prevent  or retard sulfating of the Lead Acid battery plates.  These chargers are usually the higher end 12 volt charger systems, with out a detailed spec sheet or possibly an oscilloscope its hard to tell if your charger is emitting these spikes. The spike will destroy your charge controller and the battery!

The Rotax regulator is a porcupine in this respect and I can confirm that it destroys LiFePO4 batteries.

here is the instructions i received with my battery:

Aerovoltz Batteries are very different in chemistry
and construction from a traditional lead acid
battery. Aerovoltz Batteries do not require regular
maintenance charging and will only lose less than 10%
of their total charge over a (12) month period of static
use. They are compatible with your vehicle’s charging
system and can be used in a “total loss” application.
Any automotive or motorcycle based charger is
acceptable to recharge your Aerovoltz Battery as
long as it has a auto-shut off at 14.4v to prevent over
charging. If you are a using an automatic charger, be
sure that it is not used in a automatic desulfication
mode designed for lead-acid batteries, this can damag

Yes. An oscilloscope on the output of the regulator is a truly horrifying trace. Voltage control is almost non existent and the spikes go up to very high voltages. The recommended capacitor makes little difference.
I would start with a bridge rectifier working into 12 Ohms 50Watts in parallel with
10,000 microfarads at 63 Volts then a variable TO-3 regulator IC set up to 14.2 Volts at 20 degrees Celsius.. Mount the regulator close to the battery. Across the generator terminals, put 22NF 400V to knock the spike energy down a bit.

Haven't ran any numbers, just spitballing an idea, would a small line reactor level it out? (In my experience it makes a world of difference on long run 480V 3phase surge/inrush current peaks, MAYBE it could do the same assuming it's a rectified alternating charging system if placed before the bridge rectifier)

Yeah, I really need to sit down and stick a scope on my charging system and see how bad it is..