Adding a Voltmeter to check Battery Status

[Shadow Catcher]

A volt meter is only accurate when the battery has been at rest, no in or out for a few hours.

[flboy]

A volt meter is only accurate when the battery has been at rest, no in or out for a few hours.

That is correct in a perfect world/lab. The use of the battery distorts the voltage curve and they should rest for at least 4 hours. Lithium batteries, because of their flat discharge, are even harder to determine with a voltage measurement. However, for the purposes of an RV and trying to make sure your lead acid batteries don't go below 50%, "monitoring" your batteries with a voltage based measurement is good enough and very inexpensive.

A hydrometer is not practical in an RV on a ongoing basis and the coulomb counting and the impedance spectroscopy methods can be expensive in terms of the monitors. I believe some very expensive controller/chargers may use those methods via internal computers. If I spent the money for lithium batteries, I'd buy a better monitoring system; however, the lithium batteries can be drained almost 100%, so the inverter will monitor it and shut down at 10.5 volts and the charger will stop charging when full.

The meter I have basically tells you how many amp hours I have used, however, it also is charging continually in the sun... so I just keep an eye on the voltage to make sure it stays in a good area, especially under and a moderate load. The Hydrometer can be used to check the battery health periodically (once a month) when I check the water levels since I am using lead acid batteries (that's why I like the FLA over the AGM or Gel also... plus they are very cheap relatively and last a long time if cared for properly).

[John61CT]

SmartGauge works fine, believe that can be found for under $200 delivered

[low277]

Simple battery gauges aren't perfect but they are very commonly in use on battery powered equipment. Golf carts, scissor lifts, boats and RVs. There are better more expensive gauges, meters, but for most everyday users they get the job done at a affordable cost. I like simple! Simple is good!

[bdosborn]

A volt meter is only accurate when the battery has been at rest, no in or out for a few hours.

I used to check my teardrop with a voltmeter when I got up on the morning as the battery was at rest for 8 hours or so. I could easily go a weekend without having to worry about discharging a fully charged battery too much so checking it wasn't really required till I went on longer trips. Then I upgraded to a 12v DC fridge and installed a Trimetric meter to keep a closer eye on things. However, a typical teardroper doesn't use their battery at night like we do with our fridges and heaters.

Bruce

[flboy]

Simple battery gauges aren't perfect but they are very commonly in use on battery powered equipment. Golf carts, scissor lifts, boats and RVs. There are better more expensive gauges, meters, but for most everyday users they get the job done at a affordable cost. I like simple! Simple is good!

[cdub]

I purchased a drok power meter for mine so I can see volt and amperage. I have tested it but not permanent mounted yet. Where on Van isle are you as I am in Parksville ?

[vincigj]

I use a voltmeter/ clock/thermometer all the time. Voltmeter is just for trending. Don't need lab quality for that.


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[CoventryKid]

cdub:

I purchased a drok power meter for mine so I can see volt and amperage. I have tested it but not permanent mounted yet.

Where did you get it? Locally??

Thanks!

[cdub]

I bought it through ebay as the amazon US store wont ship to Canada, and the amazon Canada site didnt have the meter i was looking for.
https://www.amazon.com/gp/product/B017B ... multimeter
hopefully I am allowed to post links.

[CoventryKid]

Thanks, cdub. Yeah, links are good!

[flboy]

I am using those meters also and they work great. The link was for a 50A shunt. Make sure you get one with a shunt for the right amount of current. If you are running an inverter greater that 500W, that meter and shunt will not measure beyond 50A. The voltmeter doesn't care. If you are just running lights and a few small things... that probably is fine.

I got the 100A shunts because I use a larger inverter and it will almost all of that if I am pushing it.

[cdub]

How did you mount the meter?
I am looking at using a Decora style Nylon plug cover and trying to cut to size. They didnt leave much area for the locking tabs to grab onto.

[CoventryKid]

cdub:

I haven't mounted the meter yet as I'm thinking I'll try and find something a little simpler - like a meter that does not require power. As Don (flboy) mentioned, he wondered whether 12V to power this meter might harm the meter (when it says it requires only 5V to power it).

As I mentioned, I'm good at wiring, just not good at electronics - I think I'd rather find a meter with 2 leads and use the KISS method.

However, to answer your question, the meter I have is a "snap-in" type - just cut a hole the right size and pop it into place which is what I want to do. It has retaining tabs on the side so no cover plate is required.

WTH, I may just try wiring it with 12V and see what happens. If it works, great. If not, plan B explained above.

[cdub]

Sorry i should have specified the question to ftboy as he used the same units I have.
The unit i bought is 6.5-100vdc so under over voltage isnt an issue.
The unit you have could be powered from a USB adapter as i believe they are 5volts.