Losing charge when idle

Hi, any suggestions why my battery gradually loses charge? Recently built 10S6P using new cells and new BMS.
What are the most likely causes of loss of charge when the battery is idle and disconnected from the motor?
It worked fine for the first few cycles.
Thanks. John.

Could be a number of issues. Can you take recordings of voltage, and how voltage drop you see over a measured period of time?

Cells do self-discharge. Some slowly but some annoyingly quickly (thinking of yesteryear's NiCd batteries, gah). Old or abused lithium cells are more subject to self-discharge than fresh ones.

Also, the BMS draws its power from the battery, sometimes only one or two cell groups. Even if the BMS isn't powering or depowering anything, it drains a very small current to stay on while it monitors voltage. This is hardly noticeable in a pack that gets used and charged frequently, but it can literally destroy a pack that's derelicted for long periods without any recharging.

Chalo said:

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Chalo, I sent you a PM ... did you get it ?

How long time are we talking about? A good li ion battery not connected to anything seems to hold most of its charge for a few years. Connected to bms it last shorter, 6 months to a year maybe?