I recently purchased a dual voltmeter/ammeter. I have connected the voltage wiring across the van battery terminals, but as there are multiple points to wire to, where do I connect the two wires to give me amp draw. The van has a solar panel on the roof with solar regulator and a battery charger in circuit when connected to 240 volt power. I would like to be able to check total current draw from the battery as well as current going into the battery from the solar panel and the battery charger when on 240 volt. Hoping someone can help with the wiring to this ammeter.
The ammeter can only read one thing at a time. So if you want to read several things then you cannot do it at one point. If you have the point at the battery terminal then it will read what is going in or out of the battery, but if the current is coming from the solar and being used at the same time in the van, for example, then only the excess going to the battery will be read.It is not simple to know everything at once
The voltmeter measures a potential difference, PD, between two points. Extremely little current goes through the meter.
Whereas, an ammeter measures the current flowing in a circuit. All of the current flows through it. Connected properly it will not affect the voltage.
Therefore if you think of a capital T, with the battery on the right hand side, the solar cells and controller on the bottom, and the van wiring (all loads and the feed from the car etc on the left, you can see that the ammeter can go in only one leg of the T at any one time.
An ammeter in the battery leg, or one in the van leg, has to be bi-directional. The one in the solar leg can be one direction only. The positive of the ammeter goes to the source while the negative goes to the load for a forward reading.
Some would wire in three ammeters to keep an eye on the whole system.
A single voltmeter, measuring DC of course, should do just with the positive wired to the centre of the T and the negative connected to the negative of the circuit - in this case the battery negative post. If the controller has a voltmeter inbuilt then that should do the job.
The key is to make all connections secure and clean, whatever the function is. For ammeters they need to be substantial as well. Poor connections bring about voltage drop, heating, current loss and failure.
Also, make sure that all connections are insulated - safe from wayward spanners, watch bands and toolboxes.
Don't forget to have a fuse or fuses in there, at least in the battery leg.
I'm only running a fridge & charging phone, camera & torches. So voltage is pretty much the same near or further from the battery. The analogue voltage meter works well.
My analogue amp meter I have wired in from the solar panels so I know how many amps they are providing. I can run the load via the MPPT & that provides a pile of information on the phone for everything but after a while you do get a pretty good feel for usage so I don't really both anymore looking at the phone.
A DC clamp meter is very useful to check everything out when designing your system & spot checks & when things go wrong. If you make a positive or negative wire accessible at key locations you could whip around with a clamp meter if you feel inclined.
