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wirehead70 avatar image

Battery Over Voltage Last 2 Days on Blue Solar MPPT 100/50 with 2 12 volt batteries at 200ah What could be wrong

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overvoltage
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JohnC avatar image
JohnC answered ·

@wirehead70

Typically, -3mV per cell per degC, so -1.67mV per degF. For a 6 cell string, then -10 mV/degF. Don't forget the minus sign.

I've seen some batts where that 3mV is 4 or even 5, so a bit mushy. I use ~4, over 24 cells, so a round -100mV with flooded batts.

So take your choice, but I think what you have now is too high. You could also reduce your Absorb setpoint a little if you want, as some batt makers give a range, as they assume most users don't have temp comp. And then don't tell you why there's a range..

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That look more like what It should be screenshot-11.png

screenshot-11.png (19.4 KiB)

@wirehead70

Yeh, that should do. If you're worried, you could pull down one of the Victron Pb battery presets to check. Should show -9mV(F) as default, but -10 is close enough.

BTW, you can create and name a preset of your own, so you won't lose it if you switch about..

Thanks JohnC I dropped it down to -9 and set the amps back to 30 we will see what the next sunny day holds. Freezing rain for today

JohnC avatar image
JohnC answered ·

Hi @wirehead70

Look to your Temperature Compensation. It seems quite cold there, so the set V's will rise.

Also, your TC setting is very high (chopped in your screenshot), much higher than I'm prepared to use. Where did you get that from?

If your temp reading is properly networked, an adjustment there should be pretty much real-time, else you may have to wait for tomorrow's startup.

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rickp avatar image
rickp answered ·

Just quickly scanning, I notice recommended amperage is 30A or less, and you’re set for 50A. I’m not sure if that can cause an over voltage situation, though.

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He has 2x batteries..