Battery drain...Can't make it one night

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magconpres

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Joined
Jul 29, 2008
Posts
53
I have a relatively new (and recently tested) group 29 house battery with a RC rating of 210.
I can't make it through the night without the battery going dead.

Went out last weekend and boondocked at around 9pm.  This was after a long day of driving and being on shore power the night before, so the house battery should have been fully charged.
We ran a few lights for a bit (I'd say less than 1 hour with maybe 2 lights), and used the water pump a few times (enough to rinse some dishes and flush the toilet).

After that it was nothing but the fridge.  Got up about 3am to start up the furnace and  the battery was too low to do so.

When I got home, I checked the drain on the battery.
Just parked with nothing on, there's about a 700 mA draw on the house battery due to the propane valve.  Starting the fridge brings it up to about 1 Amp.  lights seem to draw 1/2 an amp.

Even if I left a few lights on, there should only have been about a 2 Amp load for 6 hours....12 AH doesn't seem like much.

I had the battery tested at Interstate before I left and they said it was about 90% of ti's rating....but I'm not sure what rating they were talking about.  Maybe the CCA rating?

Do I just need a new battery at this point?  I've only had this one for about 2 years.
 

Gary RV_Wizard

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Feb 2, 2005
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74,959
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At my Silver Springs FL home
The battery load testers used in stores are usually designed to measure cranking amps, but they give a fair indication for  amp-hour capacity as well.  I don't know what 90% means either, but the fact that it is less than 100% suggests whatever they measured was less than ideal.

Each incandescent light bulb draws 0.5-1.0 amps, depending on the bulb type. Water pump doesn't run long enough to be significant overall.


Without some battery voltage or specific gravity measurements, it's hard to guess what is happening, but a weak battery is a fair guess. A fully charged 12v battery should be at 12.6v at rest, after not being charged for awhile.  With the charger active, it should show 13.3-13.6v.
 

Frank B

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Joined
Apr 23, 2005
Posts
1,465
Location
Calgary, Alberta
As Gary suggested, I would be inclined to check the actual state of charge of the battery after it has been on Shore power for a day or two. It may not be fully charged as you assume.


Cheapest way is to check the electrolyte by measuring the specific gravity with a hydrometer.
 

magconpres

Well-known member
Joined
Jul 29, 2008
Posts
53
It's on the charger now. I'll find my hydrometer and measure SG later this week.
Do I check each cell?
 
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