I would appreciate your advice and feedback regarding using Lithium Polymer batteries, to dump weight.

I learned that when "properly maintained" they last 10 years and have great power output for cranking.
Prismatic cells are safest, for fire-risk mitigation.
Battery management system (BMS) is essential feature.

It's been said that Lithium "ages" rapidly when exposed to heat: Should be in cool place like trunk!!!
(when asking AntiGravity about it, they rebutted that suggesting that engine bay does not get over 140F: I strongly disagree for Evo application, with hot water & oil at 100C+, and hot turbo with EGTs hitting 1600F of course there is high temperature)

Also, rated capacity of Lithium Polymer battery can be fully utilized, i.e. if it's 50 Ah (amp hour) battery all 50 Ah are available.
In contrast Lead Acid battery only can provide adequate voltage down to about 50% of it's rated capacity to be useful.


High price of Lithium Polymer batteries are a deterrent, and I've called manufacturers with little valuable feedback.
Seem most are repackaging some remote OEM product and are acting as Re-Branded brand-marketing & sales.
They lack basic knowledge to compute simple calculations.

When asking "what do I need" an array of options is offered, top of the line $800 is pitched, but if also $400-500 option available: some fear is passed down to instill trust into the $800 option.


I am between Miata AGM battery like Die Hard, 24lbs small and actually OEM size on Evo 5 and 6, and a Lithium Polymer.
My car is frequent driver, and I prefer not to have to use a Battery-Kill-Switch nor "trickle-charger" Maintanier.
It has only OEM silly radio, and Fuel Pumps upgrade drawing more power when at full Voltage than OEM.


Please share your wizdom and experience.

 

what you want is lithium Iron Phosphate (LiFePo 4). This chemistry is the safest and the voltage range matches a 12v lead acid battery the closest of all the lithium types. The thing to keep in mind about the lithium batteries is that their environmental tolerance is much lower than lead acid. They don't do well with low temps and can be damaged if used at freezing or below, likewise high heat will shorten their life. The reason most legit batteries will be expensive has more to do with a complex BMS then the batteries themselves. They need to be balanced, under and over volt protected, over current/short circuit protected, and temperature protected. All that while putting as low a draw on the battery as possible.

 

If you daily the car and aren't going after points, minimum comp weight, require enough amps to start 4 of our engines, etc etc etc then the AGM will exceed your requirements. You won't feel the difference of 15lbs between the two cruising or city driving. What would stop me is the fact that If you f* up and leave some accessory on going into a restaurant and drain the battery past x volts, you're about to have a long day with Li.

 

I tried to respond to your PM but it said your mailbox was full. I have a 16cell Antigravity. But my car isnt a daily and most nonessential electronics have been removed from the car. I also have the proper charger for it.

No issues to speak of with mine. If it goes bad ill just buy another one anyway.

 

I have the antigravity battery too with low voltage cuttoff. That part is pretty critical for Lithium incase you do leave something stupid on (we've all done it...). Can just hit the bypass button and fire up the car to be on your way.

The batteries are so light it takes almost nothing to keep them in place. I cut down a stock tray since its plastic and light, and use 2 high strength zipties to hold it in place. I also keep an old ETS battery in my tool box just in case something happens at the track.

My future plans though are to move it to the trunk and run a big battery and never have to think about stored electricity.

 

Yes I hear you,
V8MR, I cleaned the inbox.
Thanks for trying.

I will use Miata battery for now, and if some good development occurs, and prices become more reasonable, I may get a bettery for track use.