question

joepk avatar image
joepk asked

How to connect/ disconnect batteries with different soc?

Hello, I am sure someone had the same problem, but I cant find the answer.
i have a ESS with 10 kWh batt. The plan is to connect a golf cart with the same kind of batt. This is used a mobile powerbank. If we return home it is a little problematic to connect to the bus bars. Different soc, voltage, etc. What would be the right path to follow?

thanks in advance.

battery charging
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2 Answers
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snoobler answered ·

SoC doesn't matter.


Voltage does.


Connect only when voltage is 0.2V within each other. If > 0.2V, use a suitably rated resistor to limit current flow to something both batteries can handle.


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joepk avatar image
joepk answered ·

Mmm, isnt it correct that a lot of power is consumed bij the resistor this way? U=I*R

Edit, now that I type this it is the differnce V, only a few 0.2 V thanks to the chargecurve of LiFePo4

Thanks

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snoobler avatar image snoobler commented ·
Yep. The idea is to leave it in place temporarily until the battery voltages equalize to within the 0.2V difference, then remove it and make the connection.


This is particularly critical for Lithium batteries with a BMS that may register the surge in current as a short circuit and engage protection. It's less of a concern for lead acid.

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