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najab asked

Voltage difference between Smart Solar and Multiplus

I have a Smart Solar 250/60 connected to a Multiplus 800/24/16 and a 24V LiFePo battery using a bus bar.

While charging there is a ~0.3V difference between the voltage reported by the Smart Solar and the voltage reported by the Multiplus. As an example, at the moment the SmartSolar is reading 27.16V and the Multiplus is reading 26.86V.

I know there will be a slight voltage difference, I'm just not sure if 0.3V is expected or if it points to wiring losses. The system is remote (set up for my parents) so don't want to trouble Dad with redoing the wiring if there's not an obvious problem.


Edit: Forgot to mention, the Multiplus is in an ESS system and the load is fluctuating between 100 and 300W while it's charging.

MPPT Controllerswiring
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wkirby answered ·

You will always get a Voltage drop along a piece of copper when an electric current is flowing through it.
The amount of Voltage drop varies depending upon how much current is flowing and the resistance of the copper in that circuit, copper thickness and length. Also the resistance of the fuses etc.

If you wait until night time when the MPPT is not charging and you could minimise the current going to or from the MultiPlus, then you could expect the Voltage readings to be pretty close since the Voltage drop will also be minimised.

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najab avatar image najab commented ·
I tested again after the sun went down and the Multiplus in charger-only mode and voltage difference was under 0.1V which I can live with.

Thanks.

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