drained batteries - help

[grymsr]

yeah, I like the NAPA AGM ones too. My son and I will be crawling all around the truck to track down the problem. The dead ones are optima yellow tops from 2017, way out of warranty. Too bad. I hear optima makes fair batteries. Not as good as they were ten years ago, I'm told, but still good.

[grymsr]

Cue Twilight Zone music...
after I was about to give up on the optimas, I gave them one more shot with an old analog charger (circa 1973) and voila' they are fine.
hmmm...
still need to find why they went dead in the first place.
the quest continues...

[Nailhead]

Cue Twilight Zone music...
after I was about to give up on the optimas, I gave them one more shot with an old analog charger (circa 1973) and voila' they are fine.
hmmm...
still need to find why they went dead in the first place.
the quest continues...

I have heard that newer Optimas tend to self discharge, and experience with my own seems to bear this out. That may also be the one-wire GM alternator I have, but I have to keep the truck on a Battery Tender if I go more than a month between drives.

[grymsr]

yeah, I have the battery tender hooked up now.I'm going to mount it eventually.

[plumas.placer.miner]

This is probably a silly suggestion, but did you leave the military light switch on? The only reason I say this is because I did that and sure enough, my battery was dead the next day. haha. Learning curve.

I didn't understand the military light switch when I first bought the truck. Unlike some of the old timers on this site, I didn't drive one of these when I was in the service.

[brute4c]

Never heard of one myself until 1995...

I left mine on and ran the batteries down...unless the headlights or parking lights were on, it shouldnt though with good batteries...

The worse thing to do is leave the on off switch on after shutting the truck off...if the points are open, ok....if the points are closed, it will ruin the coil...

[grymsr]

not sure what happened but I'm extra careful to switch off. but I'm probably going to install a battery cut out switch anyway.

[Nailhead]

Never heard of one myself until 1995...

I left mine on and ran the batteries down...unless the headlights or parking lights were on, it shouldnt though with good batteries...

The worse thing to do is leave the on off switch on after shutting the truck off...if the points are open, ok....if the points are closed, it will ruin the coil...

Tenders are worth their weight in gold, Jon.

[ColoradoSpringsRob]

Thanks for that link Kwai, just ordered one. On a quest to figure out why my truck's electrical system hates me.

[Nailhead]

One thing I have learned of late researching RV batteries & solar charging systems is that different battery chemistries require different charging voltages. AGM requires a higher charging voltage than lead acid, and that is likely what has been at play with the Optima Blue Top (AGM) I have been running in my truck: the 12si alternator in it doesn't supply the higher voltage required by that battery, and consequently, the battery never gets fully charged.

A couple of months ago, I needed a battery charger to fill the hole between the Battery Tender and the Forney 60-amp roll-around charger/booster I have, so I bought (unintentionally) a charger with different charging programs for different chemistries. 24 hours later on the AGM setting, that Blue Top was fully charged for the first time in I don't know how long. This is when the light went on concerning charge voltage and that battery. I top it up occasionally now, and after every drive.