I want to install a 12V digital volt meter

Fixed Sight Training wrote:
I used a voltmeter that just plugged into the 12 v cigarette lighter. It was pretty accurate when checked with my multi meter. No drilling or wiring and I can pull it out and check other RVs or cars with it.

I have one of those and I also like it. I have decided to go down a different route for a couple reasons. (1) I already have this voltmeter that has been sitting in the tool box for a year or so and I'm motivated to install it. I think it will be more "pro" looking. (2) The 12V outlet that I've used for the plug-in voltmeter is on the same circuit as the propane detector and radio. This winter I decided to pull that fuse to reduce the parasitic draws while the TT is parked in the driveway for the winter. I have found that when my solar panels get buried under the snow, my battery voltage starts to fall behind after a few days and I'll have to plug the TT in and let the converter charge them back up to 100%. This winter I pulled that fuse and notice an improvement in maintaining battery voltage during this scenario. But to check the voltage I have that plug in meter in a different 12V outlet that is less convenient to check. It is in my pass-through storage area where my solar controller and inverter are installed. So this motivated me to come up with something better and leads back to my reason (1)! :)

As an update, I wired up the voltmeter last night to verify that I get a good 12V reading. I picked some "favorite" wire nut junctions that I confirmed with my multimeter will give me an always-hot 12V reading and wired the voltmeter directly to them. I was initially disappointed because the voltmeter consistently read 0.2V lower than what my multimeter read. My other plug-in voltmeter at the other location confirmed the multimeter reading. I went back to the amazon listing for the voltmeter and read in the reviews that the reading can be calibrated by turning a potentiometer on the rear of the unit. I confirmed that this is the case and I adjusted to voltage reading so it was the same as the multimeter reading. I'll update again when the project is finished.