I want to install a 12V digital volt meter

[ewarnerusa]

I wanted to install a digital LCD volt meter with LED backlight display that I bought off amazon. I'm familiar and comfortable with 12V electrical and I have decided to just tie into a 12V connection from behind the existing control center (where the tank/battery gauges are, water pump switch, water heater switch, etc.). I'm going to mount the volt meter above the control center. While the LED backlight would draw very little juice, I figured I'd want a way to switch it off to avoid any unnecessary parasitic loads. My plan is to wire up a switch that will turn the volt meter display on and off. I snooped around with my multimeter and there are many different wires carrying the 12V signal to choose from. My plan was to pick a favorite and tie the switch into it, then hook the meter to the switch.
Anyone have any comments or suggestions for my idea? Thanks.

[64thunderbolt]

westend, I like those analogs. Nice job.

[Bob_Vaughn]

They use off shore vendors like e-bay and amazon.....

[hershey]

Sears would have been the last place in the world I would have though to have 12v meters, and what a selection.

[westend]

Bob Vaughn wrote:
I have an analog volt meter which I do not think would hold up to the vibration of going down the road in our rv....

I have an analog meter, circuit interrupted by a switch. It fares well. I also have a Victron battery monitor and Fluke handheld. All of the meters measure close, consistently.



Sears sells a variety of 12V meters.

[hershey]

I installed the meter on our motorhome several years ago along with a toggle switch. I can't remember ever turning the switch off since installation.

[wmoses]

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.

X2. In my case the 12V outlet is in a cabinet so it is not even visible when I am not using it. I suspect that the OP want a more permanent factory-look.

Ooops ... he said that in a later post, and for good reasons. 🙂

[Bob_Vaughn]

The things I have bought on evil bay and amazon turned out to be a 6 to 8 week wait go get it....I think not....

[DrewE]

tenbear wrote:
I don't think an analog voltmeter is what you want for battery monitoring. You are really looking for voltage changes in the 12.0 to 14v range. A tenth of a volt is important. That may be hard to see on an analog meter.

I know some people use them but IMHO, a digital meter is better for this task.

If you want an analog meter, you can always hook up a 5V meter in series with a 10V zener diode or some more sophisticated voltage reference and create a 10-15V analog meter to get better precision in the readings. The meter scale would have to be recalibrated and redrawn, of course.

[tenbear]

I don't think an analog voltmeter is what you want for battery monitoring. You are really looking for voltage changes in the 12.0 to 14v range. A tenth of a volt is important. That may be hard to see on an analog meter.

I know some people use them but IMHO, a digital meter is better for this task.

[Bob_Vaughn]

I have an analog volt meter which I do not think would hold up to the vibration of going down the road in our rv....

[teddyu]

I installed a self-powered voltmeter (under $5) that monitors the auxiliary (coach) battery buss. It’s mounted in the dashboard above the Generator run-hour meter and is connected to an auxiliary (coach) battery terminal on the BCC battery isolator solenoid through a 1A fuse. This allows for continuous monitoring while driving.

By monitoring the auxiliary battery buss:
One, with the engine and shore power/generator OFF – I know the charge condition of the coach batteries. Two, with the engine ON – I know the charge condition of the coach/chassis batteries, the functionally of the BIRD, and the output of the engine alternator. And three, with shore power/generator ON – I know the charge condition of the coach/chassis batteries, functionally of the BIRD, and output of power converter.

I bought (from Jennyear on eBay) a self-powered Green 3~30V (12V) Mini Digital DC LED Battery Voltmeter and bezels (items 130875885643 & 140940500425).

[tenbear]

Bob Vaughn wrote:
Apparently Radio Shack does not sell this type of digital display. I am not a big fan of buying things on line because if it has to be sent back then the advantage is gone. Plus many times the shipping to my home is more than cost of the item then if it has to be returned that makes the cost more than driving to a local store and pick up an item....

You can buy a digital voltmeter on eBay for under $5.

I have had good luck doing this, but if it is not as you expected I have been able to get a new one without returning the old one. Just buy from sellers with good ratings and don't rate the seller until you are satisfied.

At that price you can just throw it away if all else fails.

[Bob_Vaughn]

Apparently Radio Shack does not sell this type of digital display. I am not a big fan of buying things on line because if it has to be sent back then the advantage is gone. Plus many times the shipping to my home is more than cost of the item then if it has to be returned that makes the cost more than driving to a local store and pick up an item....

[ewarnerusa]

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.

[Fixed_Sight_Tra]

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.