Voltmeter and USB ports
After using the leisure battery to power some existing circuits, stage 2 of our electrical system was to add some circuits of our own. Chief among which was a voltmeter for monitoring battery charge. We also fancied a few extra power ports in the back, for charging phones, torches, cameras etc.
The first step is to install a fusebox, we have two for the leisure battery. One powers existing factory circuits via the cars own fusebox (see earlier post) and another powers the new circuits. I prefer the single input type fusebox as it makes it easier to keep things tidy and avoid wire spaghetti. A single power line runs from the battery to the fuse box via a kill switch. This means we can cut power to the whole system easily to kill all current draw when parked for long periods and to make it easy to isolate everything when working on things. This is shown below. (I know it's a bit untidy but it's still a work in progress...)
With the fusebox in place we ordered an ebay voltmeter with USB and cigarette lighter unit. They're really cheap, ours was about a tenner. It does the job really nicely. It was very easy to wire up, just put the three components in parallel. The key to doing it well is to make sure you put it in a sensible place. Then be sure to make good crimp connections so you don't have any voltage drop and inefficiency. Keep the wires short if possible, again reducing resistance in the circuit.
Our panel is installed in the plastic side trim which is at eye level and by the shelf to put your phone on when it's charging. This works really well. I simply drilled three holes and popped it in. It is currently earthed to the bolt that formerly secured the rear seats. I'm probably going to add a direct line back to the battery for the aux circuits though.