Monitoring the condition of two batteries

I have starter battery and two more batteries in parallel, with isolator switch between starter and aux. #1 and also between aux. #1 and aux. #2. Is it possible to rig up a permanent device to continuously monitor the voltage of aux. battery #1 and aux. battery #2, and also the amps being drawn from each?

You can certainly rig up two ammeters. The simplest method is to use ammeters with a current clamp- just fit one to the positive cable of each battery and it will show current flowing in or out of each. No need to cut into the existing cables.

You can connect a voltmeter to each battery too, though when they're connected in parallel the voltages will be equal, and it's best not to have them permanently connected.The voltmeter for the starting battery can be switched through the ignition. For the auxiliary battery I'd power that via a relay which is controlled by the ignition switch.

For gauges, I think the ideal would be a dual needle gauge if such a thing exists- either a combined voltmeter/ammeter for each battery, or a dual voltmeter and dual ammeter- this would save having four separate gauges. Not aware of any specific products though.

VDO make dual volts, not sure on amps, they died out for the main part, or you could get a couple of panel mount dual meters of ebay for a few quid, just make sure you get the clamp ammeter type.

Wonder if wiring up a couple of these would work for you?

DC200A/100V Car Battery Meter Digital Amps Gauge Volt LED Ammeter 12V 24v e-BIKE | eBay

somthing like that would do, but id still look for an inductor ammeter, that one you'd need to mess about with shunts.

I have a manual switch to the solenoid connecting my batteries. A volt meter to both batteries is simply enough and you can flick the switch off to see the voltage of both. I have an ammeter on the auxiliary battery which is of the standard type i.e. no shunts. All my ancillaries run from the aux battery so lights, interior light, CB, stereo, cigarette lighters etc so this work out very well.

One thing you could try for dual volt meters is to fit cigarette lighters to each battery and then use these:

LED Car Battery Electric Cigarette Lighter Voltmeter Voltage Meter Gauge Tester | eBay

I've gone for standard volt meters but this would be a cheap way of doing it.

You could copy the setup used for twin fuel tanks and have a couple of relays switching the gauges from one battery to the other. Then you'd just need a pair of regular gauges and a switch somewhere.

FlyingPete said:

You could copy the setup used for twin fuel tanks and have a couple of relays switching the gauges from one battery to the other. Then you'd just need a pair of regular gauges and a switch somewhere.

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The problem with that is switching the ammeter. All the current used by that battery passes through the meter (unless you use a shunt). If you are using a shunt on each battery then forget the relays and just use a multi pole switch so that you can switch several things with the same switch.