question

4ncar avatar image
4ncar asked

SOC does not increase while charging ...

I have a bmv 712. When charging via battery charger/generator, the SOC does not increase. It does show the voltage increase being created by the charger, bot there is no change in SOC. I only know the batteries are charged when the charger shows 100%

BMV Battery Monitor
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1 Answer
Kevin Windrem avatar image
Kevin Windrem answered ·

Make sure nothing is connected direcly to the battery negative terminal. All loads and charging sources should be connected to the load side of the shunt.

The BMV uses a voltage trigger to reset SOC to 100% so that's independent of the charge accumulation based on battery current.

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4ncar avatar image 4ncar commented ·

Yes, nothing other then the shunt is connected to the negative battery terminal (other then the battery charger clamps). Are you saying if I connected the battery charger to the shunt negative I would see the increase?

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Kevin Windrem avatar image Kevin Windrem 4ncar commented ·

That is correct. The shunt has to sense the charging current also.

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4ncar avatar image 4ncar Kevin Windrem commented ·

Just so I’m clear, connect battery charger negative clamp to “house” side of the shunt?


thanks, Kevin!


phil

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Kevin Windrem avatar image Kevin Windrem 4ncar commented ·

Yes

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speck1956 avatar image speck1956 Kevin Windrem commented ·

I am having the same issue. I have to manually enter SOC based on voltage. The only thing I can think of is wiring 2 batteries in parallel I have to connect negative to negative so shunt cable shares that one cable. Should I hook up anather way. Thanks

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Kevin Windrem avatar image Kevin Windrem speck1956 commented ·

Both battery negatives to the BATT - on the shunt.

All loads and charging sources to the shunt Load/System -

You can parallel the batteries then send one negative to the shunt. Make sure to take the positive cable off the opposite battery.

Don't forget to set the total battery capacity in AH: If you have two 100 AH batteries in parallel, enter 200 AH.

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matias avatar image matias Kevin Windrem commented ·

Hello Kevin, can you clarify your comment to remove the "positive cable from opposite battery" ? If they are all on parallel shouldn't all the positive terminals be connected?

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Kevin Windrem avatar image Kevin Windrem matias commented ·
There is always some voltage drop in the cables regardless of how large they are. If you connect loads and charging sources to pos and neg from one battery, then the other battery will supply less energy. Taking positive from one battery and negative from the other balances that because the voltage drops are equal for both batteries.
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matias avatar image matias Kevin Windrem commented ·
Thank you.
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