Draining Rear Battery

[sandcobra164]

I'm having an issue with my M1028 and unfortunately, I'm about 640 miles away from it. My wife tried to start it to move it and cut the grass. She stated that the Gen 1 light was really dim, Gen 2 light was bright, wait light really dim and of course, it wouldn't attempt to start. She hooked up the battery charger to the front battery and it indicated 12.5 volts, rear battery, 10.2 volts. I told her to let the rear battery charge and it should be good to go. The interior light switch on the headlight switch had been left on, I guess when I left the truck for a static display and I didn't catch it. It's switched off now. Now after letting the charger cycle a few times over the last two days, it still won't start. I told her to disconnect the wires to the rear battery and try charging it like that (I'm so proud she was able to do it!). Is there anything else that could be discharging the battery or does it simply take a long time to recover and recharge a 2 year old Exide 6TL battery. I won't be able to look at it myself till the 15th, I'm wondering if something else could have been switched on that I'm not aware of. Thoughts please!!!

 

[tstone]

Your interior light operates off of the front battery as does all of the 12 volt system. The rear battery is in series with the front battery and will only be used for the starting circuit and for minimal service through the fuse block for other 24 volt requirements. I would guess that the battery is bad or is being drained down through the # 2 alternator. Test the system with a fresh battery and determine where the drain is occuring.

 

[papercu]

Even if battery is showing 12.5 volts doesn't mean the starting amps are there. Need to charge both batteries and check for 24v, STE/ICE would work great here. Good luck, Wayne

 

[doghead]

Have you rebuilt the alternators yet?

 

[sandcobra164]

Negative Sir! Might be looking into it when I get home. That's the frustrating part of it all, I won't really be able to touch it for another 13 days. I'll have the wife charge the battery, hook it up, move the truck and report what happens or if either of the Gen lights come on. I'll have her leave it hooked up for a day and check it. Then unhook it just to be safe. I don't want to ruin the battery.

 

[corelokt]

I had a battery that did the same. The battery had a hole through the case and was draining into the tray. It would actually drain the voltage. a bad cell will do the same. Leave it unconnected and see if it holds a charge.

 

[doghead]

Unfortunately, the alts do seem to go bad after the trucks have sat for a long time then put back into use.

I'd get a couple of rebuild kits and replace the small internals. Then you should be good for years.

 

[Matt65]

I'd get a couple of rebuild kits and replace the small internals. Then you should be good for years.

Here's a good source.

 

[sandcobra164]

Wife reported that she charged rear battery with it disconnected. Reconnected it (not sure if wires were good and tight) and still just clicking when she attempted to start. She said that the front battery was at 12.5 volts when she checked a few days ago. When she disconnected the rear battery after attempting to start, she said the charger only made it to 80% when it started charging. Just adding some more info. She said to heck with it, left the batteries disconnected and told me I could deal with it once I got home.

 

[sandcobra164]

Got home, slaved the truck off so it could get closer to the shed. Ran a test on the alts, all is good. Shut it off, checked for drains by testing with the voltmeter and found none with the light switch and interior lights off. Tried to recover the front battery and couldn't. It was sulfated pretty badly and was ready to be recycled. Now, a few bucks down the road, both batteries are replaced with new 6T's and the truck is ready to roll. Why did I change the back battery? It was 3 years old and I wanted them to both be ready to start the truck at anytime since this is actually my wife's MV. They'll also go dead about the same time so they are back on the same cycle so to speak. Next time, I'll save up and get some Hawkers like I have in my Deuce and this M818 that showed up one day behind the M936A2. You can discharge them to 3 volts and they'll recharge without issue!!!!