Electric Question

[defuzz]

So, I've been having problems recently with alternators and battteryies


to this end, I'd like to be able to monitor battery voltage from the cab,  to achieve this I am lookign to run a small cable from each terminal into the cab which will allow me to attach the voltmeter for constant or time to time readings of voltage.

Now, obviously  I will make sure the terminals in the cab are insulated and protected from shorting together by an errant spanner etc.... but if I were to leave the terminals in the vehiclke indefinately potentially with the voltmeter connected permantely, will it cause problems? eg will it drain the battery?

If needs be I'd put a push button on the circuit so the live terminal in the cab is only live when the button is pushed.

As you can see my electrical knowledge is pretty low..........

[ChrisW]

will it drain the battery?

Eventually yes, depends on use of vehicle and how long it stands doing nothing for.

I'd put a push button on the circuit so the live terminal in the cab is only live when the button is pushed.

Go for it  

[karloss]

Alternatively buy a proper gauge for next to nothing, wire it up properly and have constant checking of battery status with no draining. Works for me.

[Bulli]

You dont have to run a wire to the battery, all you need ot do is find an ignition live and run the earth to a suitable earth. That way the gauge will only be on when your ignition is on. There is no difference between the reading if you do it this way or run to the battery as it is one big circuit.
Hope that helps, bulli

[muddyweb]

Depends if you want to monitor the battery voltage or the system voltage.

They aren't *always* the same due to the number of connections in a vehicle loom.  If the problems he's having are being cause by a dry joint / bad earth / wiring fault  then there may well be a disparity between the voltage at the terminals and the voltage at the dashboard.


IMHO, the better solution is to fit an ammeter so you can monitor the charge / discharge of the battery, rather than just the voltage.. since that doesn't give you as much idea what is going on.  But, that is a slightly bigger job :-(

[sparkes]

for a simple monitor solution fit a fag lighter socket to the meter and plug it in there, it should be close enough.

For a propa job, fit a volt meter to the fuse box, look for a  spare relay slot and test for a constant live in its terminals

Steve

[petergalileo]

You can pick voltmeters up for a couple of ££ on ebay, you can even buy a pod to mount it in so it sits nice on the dash.  

Wire it up to a live on an accesory like the radio as voltmeters do slowly drain the battery.  If your battery is okay you wont have a problem but if its on its way out it might loose its ability to turn the engine in a few days.

Peter