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For all of you who don't have a voltmeter, I doubt you will find a deal better than this $6 digital meter:
http://www.mpja.com/08-06-13.asp?r=00000&s=21
I can't guarantee this particular meter, but I've used this source for surplus electronic parts for over a decade and they've always been great. Better yet, get TWO of these meters and monitor each battery independently. If you don't like red, they also have green and blue for a dollar more.

Being Red LEDs you can see them at night. Generally these meters use about 50mA (about 1/20th of an amp) so a meter, left on indefinitely, will drain a battery to death in about 3 months. But you can power the meter through the ignition switch so that it only comes on with the key; you lose up to about a volt, going through the truck wiring, key switch, battery disconnect, etc. but the absolute value is not as important as catching any changes in battery voltage (and my meter is hooked up this way; it drops another volt if I turn on my headlights and accessory lighting).
For the ultimate in accuracy you would want to run dedicated wires directly from the battery terminals to the meter(s) with a separate switch to connect the meters when needed; virtually any sized wiring will be acceptable for such a small current draw -- #22 AWG wire (the typical small stuff) will lose less than 2 hundredths of a volt (0.02V) after running ten feet each way to the meters. Best here to size the wires so they have enough insulation to prevent chafing, after all, they are connected right to the battery and any possible shorts will create smoke and/or flames.

My expectations for my truck are 26.5 to 28V when running (28 during the day, 26.5 at night with lights on). Most of these meters register and display the voltage many times a second, so you can catch the battery voltage when cranking -- 20-21 volts is about the minimum I expect from decent batteries. If your batteries gets down into the teens (less than 20V) you are probably in need of either new batteries or a good independent charge of the batteries.

Nice, might grab a couple of the green ones.....great idea

ouch, I just bought one that is about the same size, same colour, same features, and same voltage for $50. I might buy an extra couple of these for my aux batteries.

Where are you going to mount it?

Go down the list of items. There is one that shows volts and amps. Might be good to keep track of an aux battery.

Thanks for the tip Jim. I picked up a couple of the red ones and this panel from Daystar: After some careful knife work I got both meters to fit. I plan to mount it on the bulkhead behind the drivers seat so it's not much of a distraction at night.

That electronics outfit also carries a nice bench top variable power supply for trying out all your Pinz goodies: http://www.mpja.com/0-30V0-5A-Mini-Benc ... 1017%20PS/

Paul, I might not share anymore if you keep out-doing me! That's a beautiful job in the perfect panel!

Would this be wired directly to the batteries?

"For the ultimate in accuracy you would want to run dedicated wires directly from the battery terminals to the meter(s) with a separate switch to connect the meters when needed; virtually any sized wiring will be acceptable for such a small current draw -- #22 AWG wire (the typical small stuff) will lose less than 2 hundredths of a volt (0.02V) after running ten feet each way to the meters. Best here to size the wires so they have enough insulation to prevent chafing, after all, they are connected right to the battery and any possible shorts will create smoke and/or flames."

Jimm391730 wrote:Paul, I might not share anymore if you keep out-doing me! That's a beautiful job in the perfect panel!

Thanks Jim! Please never stop sharing - I need the inspiration

compunerdy wrote:"For the ultimate in accuracy you would want to run dedicated wires directly from the battery terminals to the meter(s) with a separate switch to connect the meters when needed; virtually any sized wiring will be acceptable for such a small current draw -- #22 AWG wire (the typical small stuff) will lose less than 2 hundredths of a volt (0.02V) after running ten feet each way to the meters. Best here to size the wires so they have enough insulation to prevent chafing, after all, they are connected right to the battery and any possible shorts will create smoke and/or flames."

Thx!

"For the ultimate in accuracy you would want to run dedicated wires directly from the battery terminals to the meter

But of course you'd still want to have a fuse to protect those wires.

But of course you'd still want to have a fuse to protect those wires.

True, and those fuses should be close to the battery connections so any possible shorts outside of the battery compartment will be protected.

For this dual voltmeter application you really need only three wires -- the negative most battery terminal, the connection between the two batteries, and the positive most battery terminal. For short protection you should fuse the wire to the connection between the batteries and fuse the positive most terminal because if either of these short to chassis there will be smoke or worse. You might think that the negative connection does not need a fuse since it is connected to the chassis and a short to the chassis would not create any problems, right? WRONG - if the battery switch is disconnected, and this wire was touching the chassis, any heavy loads (like trying to start the truck) would result in that current going through that small wire to chassis, possibly burning up the wire. This probably is not very likely to happen, but COULD happen. Fuses are used to prevent faults from burning up the wiring, and this is where a fuse to the most negative side, too, would be wise.

Stekay is right, installing fuses are very good idea.

Spring time is great for working on old projects that have been piling up. I finally got my battery meters finished. Not sure if I'll make a fancy label or not.

I used part of a dog-destroyed extension cord with ground to get the three voltage points off the main batteries. Same for the aux. each wire has an inline fuse as close to the battery as I could muster.

I have a double pole relay powered from the key that turns them on with the vehicle.





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Nice job! Where did you locate the voltage meter box?

The box is a LeGrand junction box. Ordered from France through a contracted project a few years ago. Din rail and Phoenix terminals also remnants of old contract jobs. The relays I had were too tall to fit in the box, so I have them on a rib behind the drivers seat, unprotected.

I haven't decided where to mount it, so right now it's just floating around on a cable so I can tuck it anywhere.


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