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EMD_Driver · 01-27-2015, 03:25 PM

Took the Excel to CW last week 01/20/15, to see about some slideout seals. Brought it home and backed it in it's spot under the RV port. Unhooked and put the stabilizers down. Business as usual... Or so I thought.

I went in on Sunday and pulled the bathroom vent.. Things were fine. I left the hallway incandescent light on by accident. I went out yesterday afternoon and tried putting a slide out, so I could replace a missing stove burner igniter. No juice at all... It was then, that I realized I had forgotten to plug in to shore power, when I got home last week.

I carry twin AGM 12v 75AH batteries and they were both dead as a doornail. I plugged the unit in to shore power and the converter fan came on instantly. Not knowing how badly damaged the batteries are/were, I decided to let it charge overnight.

When I went to put the bathroom vent back in, I checked the batteries. With the converter running, I had 13.41v. With the converter cut-off, I had 9.15v.

I called the battery shop, where I buy all my batteries, to ask if they had any more. I told the guy what I had done and he said they may still be salvageable. I told him the converter had been charging them for almost 24 hours and that they were very warm. He said pumping 60AMPS into them probably wouldn't work very well. He suggested putting them on an 8AMP charger, for at least 48 hours.

I put them in the garage, to let them cool down. Once they cool, I will put them on a 3-stage 8AMP charger and see what happens..

I guess we all make mistakes.. Some more expensive than others!

BradBev · 01-28-2015, 01:31 AM

Gary,

If that's your worst mistake, you're doing just fine. Over the years I've done some doozies. Worse recent was making too sharp of turn with a short bed truck. That resulted in a broken back window and a nice crease in the cab. Thanks to a good body shop in Lubbock, TX, it "never happened".

chief02 · 01-28-2015, 08:49 AM

Why would the batteries be damaged from draining? What am I missing?. Also the converter/charger most likely won't be able to recharge a fully drained battery. Take them out check water level, check each cell with a hydrometer and charge with a good charger and rechecking with a hydrometer untill charged or you determine they are bad.

twinboat · 01-28-2015, 09:02 AM

If ypu read the OP, they are AGM batteries, no caps, no water, no hydrometer. All batteries do suffer damage from sitting dead. The age and condition play a big factor in how much damage.

Good luck

Rob17 · 01-28-2015, 09:19 AM

Lead-acid batteries can be damaged if completely discharged.

How Lead Acid Batteries Work: Battery Basics from Progressive Dynamics

chief02 · 01-28-2015, 09:36 AM

Duh my bad..I missed the AGM part..thanks...I thought they died from leaving a light switch on. I understand a battery should not be left sitting or stored unless charged. Thanks

EMD_Driver · 01-28-2015, 09:46 AM

The batteries didn't sit very long, but they were about as completely discharged as possible. I pulled them out and put them on a trickle charger last night. I don't have much hope for them.

I do still have the group 27, that the dealer put new in it. I put that back in for now...

The battery compartment is big enough for two batteries. I'll probably go with a pair of 6v batteries next time...

nothermark · 01-28-2015, 09:47 AM

The lower the charge the easier to freeze damage any lead acid battery. He also should have started with the 8 amp charger and let the cell chemistry get established then gone to the big charger once he had somewhere around 12 V at the battery. Sometimes one needs to add a lamp in series as a current limit to start off bringing back a really flat battery.

EMD_Driver · 01-28-2015, 09:51 AM

Quote:

Originally Posted by nothermark

Sometimes one needs to add a lamp in series as a current limit to start off bringing back a really flat battery.

That's one I have never heard...

Thanks

nothermark · 01-28-2015, 12:35 PM

Lamp keeps the charger from faulting when the current is too high. Usually I use a headlamp or I have a few low value big power resistors. The latter are no longer common stock most places. ;-)

wa8yxm · 01-28-2015, 03:34 PM

Two Group 24 AGMs When you get around to replacing them how would you like to get a 3rd battery for free?

GC2s, are about the same price, hold 230 amp hours, per pair (you must pair them since they are six volt) that is like 3 Group 24's, they are a bit taller, but otherwise should fit in the tray.