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Top balancing then adding to current battery in production.

SeanWatts

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Jun 29, 2021
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I am currently top balancing 8, 3.2v 100ah battery hookup packs all hooked up in parallel.

I set the power supply to 3.65v, and letting it finish.

After these are top balanced, I will hook them up in series (24v), then hook up the bms.

When I go to add this new pack to my existing pack that is already hooked up to my solar setup, how much difference in voltage between the two batteries is safe?

For instance, my current battery shows it is at 27 volts. If when I go to add the new battery in parallel, at let's say 28 volts, will that be too much of a voltage rush?

Sorry if this has been discussed a bunch already. I did search, and did learn some new things, but did not find the answer to my question.
 
LiFePO4 batteries have low internal resistance and voltage deviations can indeed lead to a big rush of current. I don't remember what the voltage difference was when I did the same thing with 2 x 48V battery packs. Personally, I'm thinking they should certainly be less than 0.5V difference and maybe as close as 200mV to be safe.
 
I agree 500 mV might be a bit much. Much better at 200mV or less.
Nothing wrong with monitoring a cycle and connect as the voltage converges.
 
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