Monitoring solar powered batteries

[tokoloshe]

I have a "common negative" domestic and engine battery system, controlled by a "One: one plus two and two" switch.

My solar panel has a dual battery controller with positive and negative connections for each battery. No problems so far.

I have now installed a NASA BM2 battery monitor.

The instructions state that all negative wiring on the domestic battery should be connected to the appropriate side of the negative shunt supplied.................so far so good.

But what happens when using the additional NASA, (optional), cable which is connected to the engine battery's positive terminal? Should the negative wire from the solar controller remain connected to the engine battery's negative terminal? Or should it be connected to the shunt along with the domestic battery's other negative wiring?

 

[VicS]

Wire it exactly as shown in Fig 2 of the instruction manual http://www.nasamarine.com/images/file/BM1+-BM2+.pdf
with the battery negatives also wired as shown.

Take the domestic battery negative of the solar panel controller to the point labelled "NEGATIVE TO ALL DOMESTIC LOADS AND GENERATORS"

and the negative for the start battery to the start battery negative'

It would not matter if the two negatives go to the same point ... the above are connected anyway.

I expect your alternator negative is common with the main engine negative and comes initially to the starter battery negative as well.

Your monitor will then monitor all use and charging of the battery you consider to be the domestic battery and, via the optional connection, the start battery voltage

 

[tokoloshe]

Many thanks.

I don't like dc electrics. It goes back to a totally destroyed wiring loom on
a sooped up Ford Anglia in the 60's!