The S-10 electric pickup has an analog voltage gauge in the instrument cluster which is useful to get a general picture of how the battery voltage is changing while you drive, but hard to read with any real accuracy. The previous owner had also wired 12v and 120v wires into the center of the dash in an attempt to set up a digital volt meter on the traction batteries. But the 12v supply burnt out his volt meter, and when I purchased the truck it was dead. I bought a 200 volt LED panel display from a surplus supply house for $12 to replace it. I also added a 1A fuse on the 120v supply line in the engine compartment as a safety feature.
Unfortunately, the display I purchased requires an “isolated” power supply, so I am currently powering it using a 9V battery inside the dash. Because the LEDs draws 60mA it would drain the battery in less than a day if left on. So I installed a red push button to activate the volt meter. I calibrated it using my multi-meter, and now I can get readings down to 1/10th of a volt, which is useful to calculate an open circuit voltage when returning to the truck to double-check the Curtis 900 charge-remaining meter or to see what voltage the charger is driving the batteries to.
I purchased an isolated DC/DC power adapter that will convert the truck’s 12v accessory power down to 9v from Digikey (102-1526-ND / VWRAS2-D12-D9-SIP) and once it arrives I may wire things up so that the gauge is turned on by the ignition key powered by the 12v line, as well as being activated by the pushbutton and 9v battery when the key is not in the ignition. [I also have an LCD panel gauge that I purchased to try out (I wasn’t sure if I’d prefer the LED or LCD one, so I bought them both) which I have changed to work at a 20 volt range that I’m thinking of using to monitor the truck’s accessory battery circuit.
Update: I have upgraded this system to a dual gauge system that monitors both the 12 volt accessory system and the 120 volt traction pack.