Location For Voltmeter

I got my digital meters from EBAY/CHINA.

Mine are mounted in a LOWES PVC Three Gang specialty switch box..

All wiring goes to the battery switch location using PVC flexible conduit.

Doing alot of camping off the power grid we wanted to be able to monitor the static 12VDC feeding the trailer as well as how many DC AMPS the battery banks were producing. It is neat to watch the smart mode charging voltages changing their charge levels when you are in charge mode.

My meter panel looks like this


Mine is great and by watching the meter panel I know how long we can go without doing harm to our battery back. There are a few commercial battery monitors out there Bogart TRIMETRIC TM-2025-RV being a popular one. This comes with alarms that my homemade panels don't have...


Roy Ken

My voltmeter at the television always reads lower than others at the DC distribution center, and converter location. And I'm sure if I had one connected directly to the batteries, it would read different than the others. It has all to do w/ voltage drop, but I don't care because I have them all memorized, and they better be reading what their suppose to, or what they normally do, or I would know I have a problem.

Good point about voltage drop in the wire that goes from the charger to the batteries.

My run is about 20'also and its number 6, looks like another project to make it 4 gauge or better :-)

Thanks...

Ron W.

Different temperature? :h

I have this little digital voltmeter. I had it on its own short thin wires to the battery and it read (to one decimal place) same as my multimeter. I then decided to use it inside the trailer and used a long pair of speaker wires to the meter from the battery. All of a sudden it reads 0.1v high.

Others may be able to confirm that experience or not. YMMV, etc.

I wouldn't think the meter wiring itself would affect the meter's accuracy. The current drawn by the meter is very small.

I'm not sure if you are saying the meter as wired reads higher than it reads if connected directly to the battery, or if it is reading higher than you know the battery voltage is.

All meters are not 100% accurate, they all have a tolerance.

tenbear wrote:

BFL13 wrote:
All true, but my Trimetric and another voltmeter on a long wire to the batteries reads high. No effect from anything else drawing high amps.

I used the Trimetric's program for that to lower its reading to be the same as I get at the battery itself with a multimeter (which has a new battery so it is not reading high like they do with a low battery) (I did have to allow for the Trimetric reading to only one decimal place so it didn't round up unless at 0.5 or above.)

Could the difference be in the location of the ground wire?

Don't know. The Trimetric ground (neg) wire goes to the shunt, which then goes to the battery on a short fat wire.

The other meter is a small LED type that only reads to one decimal place. It is on a very long set of speaker wires (not sure what gauge--not very fat) and reads high by 0.1v like the Trimetric does on its long wire you get with that when you buy one.

So despite the very low amps on the meter itself, it does read high on long wire from that evidence. It may be more of a "rounding error" by being meters with only one decimal place, don't know.

BFL13 wrote:
All true, but my Trimetric and another voltmeter on a long wire to the batteries reads high. No effect from anything else drawing high amps.

I used the Trimetric's program for that to lower its reading to be the same as I get at the battery itself with a multimeter (which has a new battery so it is not reading high like they do with a low battery) (I did have to allow for the Trimetric reading to only one decimal place so it didn't round up unless at 0.5 or above.)

Could the difference be in the location of the ground wire?

tenbear wrote:

rjsurfer wrote:
Tenbear,

You said "Picking up a nearby 12v source may give you a reading higher than the battery voltage when charging the battery in boost mode. Or, maybe lower if you pick a line feeding a high current load, or if lights are on or off. "

Why would the voltage be higher? Just curious.

Thanks

Ron W.

The PD9200 and 4600 series converters put out 14.4v in boost mode. Depending on your battery bank and state of charge, the battery could be drawing 50 or even more Amps. Even a small resistance in the wire between the converter and the battery will result in a voltage drop, so the battery voltage will be lower than the converter voltage.

Many RVs have the fuse panel near the converter so the voltage in the 12v wiring will be the same as the converter voltage unless there is something drawing some current on that wire.

In my case. I have about 20' of #4 wire between the converter and the battery. At a current drain of 50A the 14.4v would be reduced to 14.15v at the battery due to that 20' of wire. There are also other voltage drops in the wiring, like circuit breakers, fuses and connectors.

All true, but my Trimetric and another voltmeter on a long wire to the batteries reads high. No effect from anything else drawing high amps.

I used the Trimetric's program for that to lower its reading to be the same as I get at the battery itself with a multimeter (which has a new battery so it is not reading high like they do with a low battery) (I did have to allow for the Trimetric reading to only one decimal place so it didn't round up unless at 0.5 or above.)

rjsurfer wrote:
Tenbear,

You said "Picking up a nearby 12v source may give you a reading higher than the battery voltage when charging the battery in boost mode. Or, maybe lower if you pick a line feeding a high current load, or if lights are on or off. "

Why would the voltage be higher? Just curious.

Thanks

Ron W.

The PD9200 and 4600 series converters put out 14.4v in boost mode. Depending on your battery bank and state of charge, the battery could be drawing 50 or even more Amps. Even a small resistance in the wire between the converter and the battery will result in a voltage drop, so the battery voltage will be lower than the converter voltage.

Many RVs have the fuse panel near the converter so the voltage in the 12v wiring will be the same as the converter voltage unless there is something drawing some current on that wire.

In my case. I have about 20' of #4 wire between the converter and the battery. At a current drain of 50A the 14.4v would be reduced to 14.15v at the battery due to that 20' of wire. There are also other voltage drops in the wiring, like circuit breakers, fuses and connectors.