question

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Paul Carmichael asked

Quattro - want to measure battery voltage

Hello all.

I want to measure all the cell voltages in my battery bank (voltage drops to 43 with 2kW load at 90% charge). I'm wondering if switching off the quattro open-circuits the battery bank. Basically, I'm hoping to avoid having to disconnect stuff.

MultiPlus Quattro Inverter Charger
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nickdb avatar image
nickdb answered ·

Afraid not, there's a large bank of caps in the inverter which will still be connected. You should have fuses in-between, convention would have these pulled to properly isolate the battery.

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Paul Carmichael avatar image Paul Carmichael commented ·
Thanks. There is a fuse, but not the type that can be pulled. I'll just have to disconnect at the fuse (away from the hydrogen). Will there be sparks?
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nickdb avatar image nickdb ♦♦ Paul Carmichael commented ·
Almost certainly. Just remember it is good practice to precharge the caps when connecting it all up again. You didn't mention which inverter, but the bigger the inverter the bigger the bank of caps. Maybe take the opportunity to install a cutoff switch for future maintenance.
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Paul Carmichael avatar image Paul Carmichael nickdb ♦♦ commented ·
"Precharge the caps"? It's a 48/8000. If I don't find a duff cell, then I'll be ditching the lot (8000 euros just 7 years ago, boo hoo!) and replacing them with lithium.
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Paul Carmichael avatar image
Paul Carmichael answered ·

Slight thread swerve. I've checked the voltages and all but one cell are at 2.23V which is correct. One cell shows 2.16V. Does anyone know if that could be contributing to my problem? I can never let the batteries go below 80% and even at 80-90% a load of 2/3kW will set the alarms going. A 4kW load will pull the voltage down to 37 and the system shuts down. They are Hoppecke opzs solar power 910ah hc100.

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nickdb avatar image nickdb ♦♦ commented ·

You need to put each cell under a constant load and see which holds its voltage. Measuring at rest won’t help you.

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