Dual battery voltage gauge setup (1 Viewer)

[OzSahara61]

Hey crew - have tried many a drawing on a napkin but not really sure so figured it's always best to ask the experts.

24v HJ61 import Landcruiser with the original 'dual battery' set up to get the 24v. The factory voltage gauge is cooked, but I also want to keep an eye on the batteries individually.
I have purchased a dual gauge with the intention of being able for the left one to read the passenger battery, right one the driver side.

I can work out how to wire them up but also want to put a switch in there so I can turn it on when I need to.

Option 1 is to use an on off on switch that turns each one on individually,
Second option is to have an on off switch that turns them both on at the same time.

My question is how exactly do I wire this up to make all that magic happen haha

Thank you in advance and ps - I may need a drawing

 

[jgranthevagrant]

I got a gauge and charging point in a little panel from Blue Sea. There is a switch that puts power to the whole panel. Haven't looked for a while, but they probably have one that has two gauges.

 

[e9999]

if you want to turn them both on or off at the same time, you can just have both use the same ground connection and put the switch on that wire. (I'm assuming that there are only 2 wires per gauge, with no separate lighting wiring.) The nice thing about voltmeters is that they don't use much power at all, so small wires and switches are fine.

 

[Mrtwooooo]

I'd look into the BlueSea OLED volt meter they sell and just don't even worry about a switch. A single volt meter pulled 15mA. So 2 would pull 30mA. The gauges can be on a month straight and only use maybe 1ah of power. Plus the display on the bluesea meters looks a lot better than the ones you've shown.

 

[AirheadNut]

if you want to turn them both on or off at the same time, you can just have both use the same ground connection and put the switch on that wire. (I'm assuming that there are only 2 wires per gauge, with no separate lighting wiring.) The nice thing about voltmeters is that they don't use much power at all, so small wires and switches are fine.

Pretty sure when measuring individual battery voltage on a 24v system you couldn't use a common ground for the gauges, otherwise one will read a single battery voltage and the other will read system voltage (24v nominal). To run individual gauges each gauge would have to be wired directly to the battery, both positive and ground, and both could be switched by a single, 2-pole switch.

 

[LandLocked93]

Another option...
One could have just a single display.
And using a 3 pole switch - ON - OFF - ON...
Switch to the left to view Passenger batt,
Switch to the right to view Driver batt,
Switch to center position to turn off display.

 

[OzSahara61]

I was going to hijack this thread - but then I realised I started it in the first place haha.
I looked into the Bluesea option but I'm happy to go with this cheaper option.
I have since got me an on-off-on switch and was wondering how difficult it would be to have it where one shows the batteries individually, while the second shows the 24v system as a whole? And third would be off.
I've tried chatGPT but strangely enough, that just confused me even more.

I'm just after a simple old diagram if anyone can help with one I've got fuses to go in there as well and I get the concept of having them wired up to show both batteries individually, just wondering on how to get it to show a total as well (my factory V gauge is cooked).
Thanks legends

 

[FrazzledHunter]

I was going to hijack this thread - but then I realised I started it in the first place haha.
I looked into the Bluesea option but I'm happy to go with this cheaper option.
I have since got me an on-off-on switch and was wondering how difficult it would be to have it where one shows the batteries individually, while the second shows the 24v system as a whole? And third would be off.
I've tried chatGPT but strangely enough, that just confused me even more.

I'm just after a simple old diagram if anyone can help with one I've got fuses to go in there as well and I get the concept of having them wired up to show both batteries individually, just wondering on how to get it to show a total as well (my factory V gauge is cooked).
Thanks legends

Disclaimer, I'm not an electrical engineer. My formal training is Chemical Engineering.
But wow this takes me all the way back to college where I was taught to program an analog computer for the purposes of monitoring instruments in pilot plants; plants whose design and size was meant to provide data in order that they be scaled up to production size. My training would tell me to apply the use of op-amps to be used as electrical summers.

The gotcha is that I think you need to have a power supply for the op amp that might be a greater voltage than the 12V batteries you are monitoring. So you might need a few 9V batteries to power the op amp.

REFS:
https://www.electronics-tutorials.ws/opamp/opamp_4.html

https://www.circuits-diy.com/summing-amplifier-or-op-amp-adder-circuit-lm358/

 

[e9999]

well, as mentioned above, it is easy to have both an individual and the sum showing at the same time on a dual display. So, not too hard to figure out the other one. Or use a switch to flip from one individual battery reading to the other while keeping the sum showing. Or get another voltmeter and stick it in the cigarette lighter if you have one, $10 maybe, no wiring.

 

[FrazzledHunter]

well, as mentioned above, it is easy to have both an individual and the sum showing at the same time on a dual display. So, not too hard to figure out the other one. Or use a switch to flip from one individual battery reading to the other while keeping the sum showing. Or get another voltmeter and stick it in the cigarette lighter if you have one, $10 maybe, no wiring.

Now that's just way too easy LOL.