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Old 01-15-2020, 01:48 AM   #278 (permalink)
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HyBro - '08 Chevy Tahoe HY2
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Originally Posted by redpoint5 View Post
I've discussed replacing the 12v lead acid battery with LiFePO4 before since the voltages (in 4s configuration) and chemistry lend itself to direct replacement. However, the downside is the inability to charge when temperatures are below freezing, higher cost, and lower energy density when compared with other lithium-ion chemistries.

This thread by Luno got me to wondering if Lithium-ion batteries could directly replace a lead acid. It may be safe to charge these batteries without a BMS considering a 4s pack is well below full charge at the standard ~14v alternator output.

Has anyone experimented with an unmanaged (no BMS) lithium-ion 12v battery replacement? What are the potential issues with this? Would LiPoly be better for any particular reason?

There are 5 Ah batteries available for $30 online that would be a fairly cheap way to experiment with.

Even if there is no way to get around needing a BMS, it should be a fairly simple matter to combine a Lithium-ion battery, BMS, current limiting resistor, and supercap into a 12v battery replacement that should last a long time and provide quick starts in any weather.
at this point a car battery size is not much more with lithium I see them with 1.733KWh =138AH for 465$ and you can get a 90AH for 150$* AGM type cells

* new from Walmart AGM H8 battery with 5 years warranty

465$ will buy you 270ah of lead acid AGM battery..

lead acid is catching up it's just a matter of time
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