RV Battery question

[4aSong]

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.

[Chuck_thehammer]

quasi wrote:
Good question Fulltimer50. The short answer is yes, the procedure for testing a deep cycle (RV) lead acid battery is the same as for a starting battery. For the long answer and the definitive way to properly test a lead acid battery,check out www.pacificpowerbatteries.com, scroll down and click on battery school then deep cycle batteries.

(For some reason, I can't paste the link in this response.)

There's more to testing a battery properly than clamping a load tester and reading a go/no-go gauge. (Release the Trolls . . . )

Jim

You are so CORRECT,,, a lead acid battery (most) is just 2 items from being a life form...

and a 12.6 volt battery is really (6) 2.1 volt batteries...
each its own chamber.. and LIFE.
and 1 under performer affects the other 5. directly or indirectly.

43 years in the business .. I learned a few things.

[quasi]

Good question Fulltimer50. The short answer is yes, the procedure for testing a deep cycle (RV) lead acid battery is the same as for a starting battery. For the long answer and the definitive way to properly test a lead acid battery,check out www.pacificpowerbatteries.com, scroll down and click on battery school then deep cycle batteries.

(For some reason, I can't paste the link in this response.)

There's more to testing a battery properly than clamping a load tester and reading a go/no-go gauge. (Release the Trolls . . . )

Jim

[Boon_Docker]

Fulltimer50 wrote:
Is a load test designed for a starting battery going to be a useful test for a RV use battery?

Yes, it will work just fine.

[Veebyes]

Fulltimer50 wrote:
Is a load test designed for a starting battery going to be a useful test for a RV use battery?

Are you serious or stirring the pot?

[Fulltimer50]

Is a load test designed for a starting battery going to be a useful test for a RV use battery?

[bexparza]

Chuck's post above is right on the money. Have it load tested.

[Chuck_thehammer]

Veebyes wrote:

Chuck_thehammer wrote:
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...

Having your own is good. For $30-$40 saves the hassel of lugging the battery to Autozone, or whoever, & bringing it back.

You are Correct..
as I am a retired auto mechanic.. all of my STUFF is at home....
100 amp load tester...
1000 amp meter. yes 1000 amp (starter testing)
2 tool chests...etc. a ton of air tools... you name it.

but most do not own one .. an may test a battery every 8 years or so.

and where can you find a TRUE 100 amp load tester for 40 bucks?
mine was over 150.. 20 years ago.

[Veebyes]

Chuck_thehammer wrote:
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...

Having your own is good. For $30-$40 saves the hassel of lugging the battery to Autozone, or whoever, & bringing it back.

[quasi]

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.

[Chuck_thehammer]

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...

[4aSong]

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]

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]

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.