I purchased a new, old stock gimbal which came with four 18650 batteries. Two are in the gimbal and two still wrapped. To my disappointment the two installed batteries were dead. For some reason the manufacturer installed the batteries in the gimbal without a plastic separator so the batteries aren’t in circuit. I measured the open voltage at 0.340 volts and the other was 1.4 volts. The two unused batteries measured 3.8 volts each so that’s good. Is it OK to charge and use the dead batteries or are they bombs at this point? I am currently charging them at 0.25 amps and monitoring the temperature.
I would probably still use the one with more than 1V for low current applications, but the opther one would be too unsafe for me.
And please note it on the battery that it was discharged to 1.4V so you don’t forget
Just had a brand new 14500 beeing killed by a defective driver. Had 0.00V but was fine after recharging via lab PSU - I threw it away anyway, those batteries are too cheap to risk it.
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Anything that was discharged below 2-2.5V resting voltage goes straight to recycling. Deep discharged cells start forming copper dendrites on the cathode which can pierce or at least weaken the separator and short out the cell which leads to a strongly exothermal reaction, particularly when you add more energy by charging it.
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Personally the 0.340V would be an instant ‘write-off’ for me and the 1.4V is also below what I feel comfortable, trying to safe that battery, certainly with the (in general) relatively affordable prices for 18650’s.
A question: how are the batteries placed/connected in the gimbal. Are it 2 (regular) unprotected 18650’s that are inserted seperately? And are they connected in series or in parallel?
It’s always a good practice to couple a pair of closely matching Li-ion cells when they go in the same appliance, but certainly when they are in series. (Think of matching like: identical cells/same capacity, same age, same number of charge/discharge cycles they had, etc.)
So even if you managed to save only one of those cells and would match it with a brand new identical cell, there might (and probably will) an imbalance between the 2 and in a series connection that would not be preferable.
So personally I would just go for 2 new (matching) 18650’s and keep that pair together for the Gimbal. If you still want to use one of the revived cells, do what @L4M4 stated: use it in a low current application (which requires a single 18650).
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No, I’m not from that opinion. I have some 14500 and 18650 batteries very, well below 2 volts, and continue to work without any problems. Be careful, I am not saying that this is good, or that it does not affect the battery. I am saying that, definitely, they can continue to be used despite that deep discharge, but they will have lost a small part of their good original performance.
Yes they are individual cells not in a pack. They appear to be unprotected cells since they are shorter than my protected cell. The batteries are inserted parallel and I would’ve thought they should have the same voltage as they try to equalize each other.
That is also what I would normally suspect to happen.
It makes me wonder if they are actually used in parallel, or that they are just inserted in the same orientation, but that they’re not actually (parallel) connected, but that both batteries power different circuits/functions. If that would be the case, then it could possibly also explain the diffent voltages, if both circuits have different levels of parasitic drain.
It would be curious setup though, if that would really be the case, since they’re often powered by just a single battery(pack).
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Depending on where you are in the world, cells are pretty inexpensive- I’m on team “recycle and buy new”. Of course, you are free to do what you want with the cells, but know that if you have issues, it’s your fault, not the manufacturer. Most datasheets have a “do not recharge below X.XV”, if you’ve legitimate cells you could look up the datasheets.
Depending on the quality of the cells that were originally included, new 18650s might have significantly higher capacity (and therefore longer runtime).
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