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daveadams asked

Voltage Drop

I have installed the following equipment in my motorhome:

200AH Chins LiFeP04 @ 12V

MultiPlus Compact 12-2000-80/120

BMV-712

SmartSolar MPPT 100-50

525W solar panels

Orion TR 12-12-30 DC-DC charger between chassis battery/alternator and coach batteries.


System is performing well. I have one question/ observation though….

The Orion DC-DC is located at the front of the rig, about a 25ft. run to the coach batteries. I’m seeing an approx .6-.7 volt drop across the #4awg battery cables (already there when I bought it) when charging @ 25-30A. I have the absorption voltage on all 3 chargers set to 14.2V. So, the Orion is hitting the absorb voltage and dropping into float when the batteries are actually only at 13.5-6.

Is this an issue? Should I raise the absorb voltage on this charger to compensate for the IR drop ? The other chargers don’t have this issue as they are connected via 2/0 cables & short runs to the batteries.

battery charging
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kevgermany avatar image kevgermany ♦♦ commented ·
Better to move the Orion close to the batteries. Voltage drop is proportional to current. So compensating with an increased absorb will cause over voltage at the battery as the current drops. You'll get better balance between the chargers that way as well.
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daveadams avatar image daveadams kevgermany ♦♦ commented ·
Yeah, I can’t do that easily. There’s an emergency bypass relay under the hood that enables the coach batteries to start the truck in the case the truck battery goes flat. The Orion needs to be close to that relay, unfortunately.
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