How much juice is in your 12 Volt Battery?

Have you ever guessed how much power is still left in your 12 volt RV battery bank, after you had cloudy and windless days? No sun for the solar panels and no wind for the wind generator. You are wondering if you should fire up the gas or diesel generator because you are not plugged into a power outlet somewhere. The scenery is fantastic you are boondocking and like to stay where you are, had numerous lights burning and watched a movie on the TV last night. Life is good.

A three or four digit 12 V digital voltmeter gauge could tell you easy the state of charge in your battery bank and when it is time to charge your battery.  Running the voltage of your battery bank too low will decrease the lifespan of your batteries. Replacing the batteries cost plenty dollars but buying and installing a decent digital voltmeter gauge is dramatically cheaper. The meter I liked and going to install was only $17.99 for the blue, or $19.97 for the red one incl. free shipping at Amazon. That meter handles voltage between 0-15 VDC

Why a digital voltmeter and not the older fashion analog voltmeter, the one with the moving needle? Analog meters are prone to error; reading from an angle makes it hard to get an accurate reading. A 12 volt analog meter can be off by up to 30% of the actual reading vice versa a digital 12 voltmeter with only a 0.5 - 3% error margin of the actual voltage!

Here is a good table for the state of charge for AGM Batteries, like the one we have on our Jayco travel trailer.

12.8 v - 100%

12.7 v -    90%

12.6 v -    80%

12.5 v -    70%

12.3 v -    60%

12.2 v -    50%

12.0 v -    40%

11.8 v -    30%

11.7 v -    20%

11.5 v -    10%

11.4 v -       0%

Look at the 24. November 2015 write up about AGM Batteries on this blog!

Depleting the charge of deep cycle or starter batteries below of the 50% state of charge, will cut down the lifespan of the batteries. When you read 12.2 volt on your digital voltmeter gauge, it is definitely time to do some good and charge up your house bank.

Following are some pictures about the easy installation of a digital voltmeter gauge on our Jayco travel trailer!

Voltmeter purchase from Amazon

Voltmeter with packing and instructions

Me (Benno) drilling 2" hole into cabinet with hole saw

RV carbon monoxide/propan gas alarm hanging out

and new hole for meter

Hanging meter wired to carbon monoxide/propane gas alarm

12 volt supply wire

Installed meter

After the installation I thought we deserved a nice meal!