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SOC estimation of LFP battery packs
Posted: Sun Apr 07, 2024 6:24 pm
by m.art.y
So as the LFP packs are starting to be used in OEM EVs more widely wonder what chances do we have to use those in projects and conversions? Mainly it is difficult to determine how much charge they have left. What would be our options for BMS and SOC estimation? Would hacking the OEM BMS be a necessity or some aftermarket solutions exist?
Re: SOC estimation of LFP battery packs
Posted: Sun Apr 07, 2024 6:40 pm
by arber333
m.art.y wrote: ↑Sun Apr 07, 2024 6:24 pm
So as the LFP packs are starting to be used in OEM EVs more widely wonder what chances do we have to use those in projects and conversions? Mainly it is difficult to determine how much charge they have left. What would be our options for BMS and SOC estimation? Would hacking the OEM BMS be a necessity or some aftermarket solutions exist?
Well yes. Directly you can order this Wattmeter for HV application
https://de.aliexpress.com/item/10050044 ... ry_from%3A
This one is for lower voltage
https://de.aliexpress.com/item/10050060 ... ry_from%3A
Re: SOC estimation of LFP battery packs
Posted: Mon Apr 08, 2024 9:59 am
by johu
The OI 16-channel BMS is supposed the be accurate enough to estimate LFP SoC. But it needs a 2 hour resting period because the dielectric effects take super long to taper off.
As always hacking the OEM BMS would be the premier approach
Re: SOC estimation of LFP battery packs
Posted: Mon Apr 08, 2024 12:47 pm
by uhi22
Isn't counting watthours after a full charge the only necessary thing? Is it necessary to use the voltage for SOC estimation?
Re: SOC estimation of LFP battery packs
Posted: Mon Apr 08, 2024 2:29 pm
by johu
uhi22 wrote: ↑Mon Apr 08, 2024 12:47 pm
Isn't counting watthours after a full charge the only necessary thing? Is it necessary to use the voltage for SOC estimation?
Yes, amp hours in fact. But then you need to know what the actual capacity is plus you drift away over time because of measurement tolerance