Thread: Race battery
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      12-17-2021, 08:23 AM   #12

Drives: 135i N55
Join Date: Jan 2017
Location: NY

iTrader: (0)

Originally Posted by joeo View Post
I was able to leave it in the garage for 2 maybe even 3 weeks and it started fine. Car is only used for track; not a daily.
I'm not convinced that the battery management handles the factory charging system correctly.

What charger are you using?
I think it has more to do with cranking a large engine with a tiny 4lb Li battery. That deep discharge upon cranking reduces the battery life. I say this because like above I mentioned the 20lb AGM batteries for which the car was coded correctly (30ah or maybe 40ah?) AGM charging profile. When you are using a battery that is 1/10 to 1/15 the size of the stock battery you kind of have to lower your expectations on how long it's going to last... at least that is what I have rationalized the issue to be.

Maybe it is a charging issue but with how little I drive the car I doubt ~2-3,000 miles per year of alternator output would kill the battery life especially in the case of the 20lb AGM batteries that were coded correctly. It's the deep discharges. I believe the PCM attached to these LI batteries will clip the charging voltage if it goes too high protecting the battery... and the charge current not matching will affect how long the battery takes to re-charge not so much the battery life... source:

Li charging profile and charger is ideal but I don't think it impacts the battery life as much as lead acid/agm profiles for the reasons mentioned in the article. Li doesn't care if it is at 50% capacity. Lead acid/agm does and needs to be recharged before being discharged again. Li does care about being discharged deeply and rapidly though (cranking).

If you go for anti-gravity, DO NOT get the "restart" battery. It is useless for a car. You'll have to crawl through your trunk to press the restart button and then pray the battery even has enough capacity left to crank the car. anti-gravity now recommends their "HD" battery for car applications. HD specifically targets improvements to support cranking a car (power/capacity). The atx20-HD is what I would go for but it does cost a few dollars more than the RS version.

Last edited by bbnks2; 12-17-2021 at 08:37 AM..
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