Cheap Battery monitor.

[Cuppa]

I think you’ve got it Sooty. I would do as MT suggests.

Seems there are different types of shunt for different purposes just to confuse things, but in our case we are talking about a shunt for measuring current.

An ammeter shunt allows the measurement of current values too large to be directly measured by a particular ammeter. In this case the shunt, a manganinresistor of accurately known resistance, is placed in series with the load so that all of the current to be measured will flow through it. In order not to disrupt thecircuit, the resistance of the shunt is normally very small. The voltage drop across the shunt is proportional to the current flowing through it and since its resistance is known, a voltmeter connected across the shunt can be scaled to directly display the current value.

from http://en.wikipedia.org/wiki/Shunt_(...rent_measuring

A diagram from my Nasa BM1 ‘Compact’ Manual, showing the shunt installation.

screenshot_159.png

Your diagram + shunt