Battery Voltmeter Installation Question

mabynack wrote:
Is it wired in parallel across the warning lights or in series?

Definitely NOT in series. Always in parallel.

I don't recall specifically what wires I connected to, but they are behind that panel above the meter. And it really doesn't matter. You just need to connect across a +12V and a -12V pair of wires. Your meter will have at least two wires, a + and a -. Some have additional wires for a power supply or a backlight. Those will still work, but the simplest versions just have the 2 wires, and the internal power supply and backlight are all on the same source. It is not necessary to use the wires that go to your existing monitor panel. Any 12V wiring anywhere in the trailer will work.

Here are a couple of different meters that look like they should work fine.

https://www.amazon.com/dp/B00E1CW7FY/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=374PCOJ0N57ZQ&coliid=I1G7N6FCFI49K7

https://www.amazon.com/dp/B00H8KNQUQ/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=374PCOJ0N57ZQ&coliid=IE381E0RNCUJC

Those are both 4 digit, which will read hundredths of a volt.

If you want to keep it plug and play simple, you could get this Voltminder model. It is the same thing I have in the pics above, but it appears it has been remodeled a bit and a fuse added to the cable. It's a little too expensive in my opinion, but the simplicity might appeal. Just plug it into your cigar lighter socket. Hard wire it in later if you want.

http://www.voltminder.com/

bpounds wrote:

mabynack wrote:
Unfortunately the post is now moot since my cat knocked the voltmeter off the counter and the dog crushed it into little pieces.

That's too bad. Fortunately small digital meter panels are very inexpensive.

Just a simple voltmeter is one of the most useful additions I have done to our last two trailers. It's just so simple and with a little experience with it, you'll know a lot about the level of charge in your batteries, as well as what draws a lot of current, and what doesn't. Not to the digital level that a Trimetric can provide, but so much simpler, and at the campsite, just as useful.

I've had the one below for many years. Originally it had a cigar lighter plug on one end, and was intended for use in a truck cab. Has a low battery alarm and beeps. Eventually I wired it in directly. There are better meters out there now. I would insist that it displays hundredths of a volt, like the one below does. You will find that 4th digit is useful. The low voltage alarm and beeping is not really useful to me.

Is it wired in parallel across the warning lights or in series?

+1 Mr Wizard.

You can see it readily on the meter. Watch it while your generator is running, then cut the power. The voltage will drop immediately, then taper downward. You can watch it, and within an hour or less it will have stabilized. I do agree that it is still artificially high and is not a true indicator of amps available. But that does not mean it has no value. You will definitely know when you need to run the genset again to prevent excessive discharge.

It doesn't take an 8 hour wait to get the true voltage, when you are camping and have loads on the battery, in our case there are 8 fans running right now
It only takes a few minutes with a light load to remove surface charge and give you a battery under load True Voltage
Reading

mabynack wrote:
Unfortunately the post is now moot since my cat knocked the voltmeter off the counter and the dog crushed it into little pieces.

That's too bad. Fortunately small digital meter panels are very inexpensive.

Just a simple voltmeter is one of the most useful additions I have done to our last two trailers. It's just so simple and with a little experience with it, you'll know a lot about the level of charge in your batteries, as well as what draws a lot of current, and what doesn't. Not to the digital level that a Trimetric can provide, but so much simpler, and at the campsite, just as useful.

I've had the one below for many years. Originally it had a cigar lighter plug on one end, and was intended for use in a truck cab. Has a low battery alarm and beeps. Eventually I wired it in directly. There are better meters out there now. I would insist that it displays hundredths of a volt, like the one below does. You will find that 4th digit is useful. The low voltage alarm and beeping is not really useful to me.

Unfortunately the post is now moot since my cat knocked the voltmeter off the counter and the dog crushed it into little pieces.

I think you will find the voltmeter will say the same as the voltage monitor lights and not be helpful. As someone mentioned, when plugged into shore power the lights and voltmeter see the charging voltage. Even after unplugging, the surface charge in the battery will be at the charging voltage, only gradually decreasing to give a decent indication of state of charge 8 hours or more after all charging is stopped.

When you are tired of unplugging for 8 hours to measure the voltage, you will have to buy a battery monitor that keeps track of the charge (amp-hours) going into and out of the batteries. Only that provides an accurate per cent of full charge. I have a $30 one from China via eBay that works well for me.

never mind. not worth it.

JWRoberts wrote:
As a retired electrical engineer, I assure you there will be NO difference. A digital meter draws micro amps of current from the measuring point so no significant voltage drop will exist.

I have seen quite a difference when moving 50+ amps in the same wire.

mabynack wrote:
Thanks folks.

There is NO difference in high or low voltage DC. The voltage has NOTHING to do with the voltage drop in the wire. It is the amount of current flowing in the wire and it is the same with DC current or RMS AC current.

And if you are getting .5V drop in the wiring, you should clean and tighten your connections. If that doesn't do it, then your wire is too small.