We have two group 24 Interstate installed and recently we noticed they were not holding a charge (ie, after being fully charged and no load on them they dropped down to a low of 12.04v.in less than 8 hours.)After fully recharging them once again the voltage has remained at 12.91v for over 2 day with no load (cannot understand the 12.91v as 12.6 is 100% charged. Question is, can bad battery's show a higher voltage than 12.6v when they are failing? I am totally confused by this and any assistance would be appreciated.

Maybe the surface charge had not completely dissipated. That can take a couple of days if there isn't a load on the batteries.There is some measurement tolerance on meters also.

How do you measure them ? What did you use to measure voltage ?Were they removed from your rig ? All wiring removed from terminals ?

How do you measure them ? What did you use to measure voltage ?I have hardwired in the unit the Volt Minder 12 Volt Battery Alarm from Universal Power - Part 71730The Volt Minder 12 Volt Battery Alarm from Universal Power gives a digital readout of battery voltage, and has a settable battery voltage audible alarm. This can prevent starting issues, and battery damage from over-discharge conditions. The readout can also be used to verify battery charger or alternator function. These come with lighter plug adapters installed, but could be hardwired if desired. They have an illuminated LCD, for easy nighttime viewing. The lighted LCD display is a negligible milliamp draw. There are numerous inexpensive digital meters around, most of which are inaccurate up to a couple of tenths, which is huge in battery management. These are among the most accurate we found, down to the hundredths of a volt. These are mountable, or can be used as a portable meter, and are excellent for industrial equipment or any 12 volt battery, or battery system. Were they removed from your rig ? All wiring removed from terminals ? No, still connected.

only way to properly TEST a battery .... is a 100 amp load test..most auto part stores test batteries.. just make sure its a 100 amp test.. all others are a waste of time...think of battery power as water for a minute..1 oz of water is 12 volts.5 gallons of water is 12 volts.the amount of water is the WORK.. not that water is there.so you can have 12 volts and almost no amps.so no work can be done...

In order to charge a battery to a nominal 12.6 volts, the charger will supply well over 13 volts. With only the battery's internal loss, they may retain the higher voltage for a time. My concern would be why the voltage dropped off initially and why the charger allowed the charging to continue beyond the normal set point.

RV Battery question | Good Sam Community

4aSong
Explorer
Feb 05, 2016
How do you measure them ? What did you use to measure voltage ?

I have hardwired in the unit the
Volt Minder 12 Volt Battery Alarm from Universal Power - Part 71730

The Volt Minder 12 Volt Battery Alarm from Universal Power gives a digital readout of battery voltage, and has a settable battery voltage audible alarm. This can prevent starting issues, and battery damage from over-discharge conditions. The readout can also be used to verify battery charger or alternator function. These come with lighter plug adapters installed, but could be hardwired if desired. They have an illuminated LCD, for easy nighttime viewing. The lighted LCD display is a negligible milliamp draw. There are numerous inexpensive digital meters around, most of which are inaccurate up to a couple of tenths, which is huge in battery management. These are among the most accurate we found, down to the hundredths of a volt. These are mountable, or can be used as a portable meter, and are excellent for industrial equipment or any 12 volt battery, or battery system.

Were they removed from your rig ? All wiring removed from terminals ?

No, still connected.
GoPackGo
Explorer
Feb 05, 2016
How do you measure them ? What did you use to measure voltage ?

Were they removed from your rig ? All wiring removed from terminals ?
Clay_L
Explorer
Feb 05, 2016
Maybe the surface charge had not completely dissipated. That can take a couple of days if there isn't a load on the batteries.There is some measurement tolerance on meters also.

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