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How to determine the health state of a LiPo battery?

obones

Hello,

I have taken out those two batteries from a device that needs both.
Clearly, the one on the right is dead and needs replacing.

image

However, I'm wondering about the state of the one on the left as it was manufactured at the same time.

Considering how expensive it is to come by the same model in France, I'd rather avoid buying two when one would be enough.

Here, I have a bench power supply, a bench DMM, an oscilloscope, a few ESP32s or arduino, even a RedPitaya but I doubt this one would be of any help here without specialized apparatus.

Many thanks for any suggestion.

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  • 0

    Hi,

    If the unloaded terminal voltage (i.e. just apply multimeter to the terminals with the battery disconnected from the equipment) is lower than about 3.0V, then it's likely a risk to use it, some damage may have occurred. I've had that occur from new, with a lithium ion battery which was clearly in storage for many years before I received it, and it puffed up on the first charge.

    On the other hand, some batteries won't puff up and will appear to work again when deliberately charged even though inside the equipment the battery charger circuit would refuse to charge due to the low voltage, and even measured values like 88-90% of cell capacity by charging fully and then discharging through a load, but it would be hard to trust them.

    Beyond that it's hard to measure much else; the cell internal resistance needs a more involved measurement with extra equipment (AC measurement), and won't help much anyway, unless you had known good batteries to compare with at different amounts of charge.

  • 0 in reply to shabaz

    Thanks, I measured that and they both give around 3.6V which feels inconclusive, especially for the puffed one.

  • 0 in reply to obones

    Puffed up batteries continue to work : ) But you know you need to replace that one.

    What's not good is if the non-puffed up one is below about 3.0V, because then it's a higher risk to try to charge and use that.

    In other words: below 3.0V, replace. Above 3.0V and not puffed up: use your judgement, since you have no way of measuring and comparing internal resistance with a spec or known good battery. 

    (Personally if it were me, if in any doubt, I'd replace it, because that is quite a high capacity cell).

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  • 0 in reply to obones

    Puffed up batteries continue to work : ) But you know you need to replace that one.

    What's not good is if the non-puffed up one is below about 3.0V, because then it's a higher risk to try to charge and use that.

    In other words: below 3.0V, replace. Above 3.0V and not puffed up: use your judgement, since you have no way of measuring and comparing internal resistance with a spec or known good battery. 

    (Personally if it were me, if in any doubt, I'd replace it, because that is quite a high capacity cell).

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