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Oct 20, 2015, 12:49 AM
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parallel charged with a defective parallel cable question.

I parallel charged two batteries. The main battery cable was defective so only one of the two batteries was connected to the charger.

I had both batteries hooked together in parallel with their balance leads and that was connected to the charger.

My question is since I was charging at a high rate that would be fine for two batteries but not one battery, could I have damaged the battery by only having one hooked up to the charger or because they were hooked together in parallel with the balance leads it would charge both and distribute the charge between the two batteries even though only one battery main wires were connected to the charger.

Balance lead wires are actually thicker gauge than the main battery wires.
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Oct 20, 2015, 02:47 AM
Registered User
A lot depends on how "clever" your charger is, but it could damage a battery, as you have said. If the balancing currents flow between the cells in the two batteries quickly, the charger might not notice anything wrong.

It's a strange battery that has thicker balance leads than the main leads, but that might have been good in this case because the two outer wires in the balance leads are connected to the same place as the two main leads, so effectively your second pack's main leads were connected to the charger, albeit via a different route.
Oct 20, 2015, 12:51 PM
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I charge my 3S batteries in parallel every time I charge them. In order to save time I will plug in one or two small 2S batteries into the unused 2S balance connectors on the parallel board. They are charged through the balance connector as your batteries were.

I am not recommending this practice at all especially for larger batteries but you very likely charged your batteries (one through the balance lead) so everything is good—for now.
Oct 20, 2015, 09:33 PM
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Yeah that is what I am seeing. I created a 3s2p 18650 battery pack for heated clothing.

The funny thing is the balance lead wires I put on are 22 gauge, but the main dc connector pigtail I put on is like 26 gauge it is very small.

SInce the outer balance wires are connected exactly where the main battery wires are you would think it would charge both.

The only thing I don't know is that it is slightly a longer connection to go through the balance leads. But does this even matter?

I agree it probably doesn't. I just built these packs and only charged them like this for 10 minutes before realizing.

The Panasonic NCR18650 calls for .5c charge rate and If one battery only got charged I would have charged it close to 1c. But someone who was experimenting charging these at 1c said that they really killed the life by charging them at 1c.
Oct 23, 2015, 12:05 PM
Registered User
As long as it didn't burn up the balance leads the batteries will be fine. With the balance leads in parallel the batteries were in parallel even if only one had the main connector plugged in.

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