Battery BMS replacement LIPo4

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mtdandy   10 µW

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Battery BMS replacement LIPo4

Post by mtdandy » Jan 08 2018 9:08pm

G'day. I have a 48v 25a LiPO4 battery i use on my ebike. The battery shuts down at around 48v and it should be 45v. The manufacturer (China) has sent me another BMS to suit the battery and i was wondering if someone was able to install the new BMS for me. Any info much appreciated. Cheers. Brian in Melbourne Australia.

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amberwolf   100 GW

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Re: Battery BMS replacement LIPo4

Post by amberwolf » Jan 08 2018 11:34pm

Most likely there is nothing wrong with the BMS, and it is just doing it's job: it is probably shutting down the pack to protect against overdischarging a cell (group) that is dropping below LVC under load faster/further than others do.

What are the voltages of the individual cell groups as measured at the sense wires on the BMS? Measure them both without a load, and under load, at the low end of charge (and you can also check them at the high end, but definitely do it at the low end when almost empty).

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fechter   100 GW

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Re: Battery BMS replacement LIPo4

Post by fechter » Jan 09 2018 9:20am

Right, the BMS doesn't respond to a particular pack voltage, it shuts down when any single cell reaches the low cutoff point, which should be around 2.75v or so. It's possible you have one (or more) cells that are weaker than the others and it's shutting off to protect it.
"One test is worth a thousand opinions"

mtdandy   10 µW

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Re: Battery BMS replacement LIPo4

Post by mtdandy » Jan 21 2018 7:00pm

Thanks for the 2 replies. I understand them both. Im looking for someone with good knowledge and skills to be able to test the LiPO4 battery for me, and see if the BMS needs changing. The battery is shrink wrapped and so it needs opening up and i am not that steady handed or confident to be testing the BMS or the cells for voltage. My email address is vk3fidx@gmail.com.

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