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Another Renogy BMS Newbie

clint.fish

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Joined
Aug 11, 2022
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Hello forum!
I've been reading some threads about the wiring for the Renogy BMS. Seems I've got everything right.
Still not seeing any incoming charge.
Battery negative, and only battery negative connected to the B-, everything else connects though the P-.

Note, my redarc 1250BCDC has a negative terminal, but that runs to the main vehicles battery. There is no direct negative connection between the charger and the battery, unless it's it's inside the charger itself. The black lead comes out of the charger, and straight to the vehicles battery.
Should I be connecting this to the negative battery bank of the canopy also, even though my lithiums are in that circuit?
 

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I'm not clear on what your setup is. The DC-DC charger, if it doesn't support both positive and negative leads, assumes that the battery that is the charge target uses the same ground (negative) as the battery that is the source of the charge. If that connection isn't made then there won't be any current going into the target battery.

The above is what I think is called a non-isolated charger. An isolated charger has positive and negative leads on both the input and output sides and therefore does not rely on a common ground (negative).

Technically, what you have there is not a BMS. At least not what most of us think as a BMS, which is used to monitor a battery and all the cells within that battery and act when there is a high/low voltage situation for either the battery or any of the cells. You have a shunt.
 
Connect the P- to: vehicle chassis/body/frame/ Redarc negative/ starter battery negative, in addition to your load circuits.

The house battery effective 'negative' is now P-, no other negative cable should be connected to the house battery negative battery post except B- and other negative battery posts if you have batteries in parallel.

The Renogy unit is a battery monitor , the sampler that you wired in series with the house battery, monitors current flow Into and out from the battery . It in no way controls charging, just displays battery status.

The term BMS is used for electronic circuits that monitor and protect lithium cells that make up a lithium battery.

The Redarc controller has a high 14.5 charge voltage that may cause battery shutdown due to its Internal BMS detecting cell over volts.

Mike
 
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