Do I Need New Batteries?

[richp]

Hi,

I've been working at a remote ranger station in eastern Utah. After a week or more sitting quietly, my 2009 DMAX needed a jump and boost to start. Deader than a doornail -- wouldn't even work the power door locks....

So when it finally starts, the ammeter stays on "9" for a minute or two, and then slowly climbs to a bit over "14". Truck ran OK over about 20 miles. The next day it starts OK, the ammeter goes to about "11" and stays there for a few miles, then goes to "14" or so.

I decide to take it to a dealer (the closest one being 45 miles away), where they find nothing wrong. No codes, battery voltages OK. Since I'm located so far from them, there is no chance of leaving it overnight for an AM diagnosis.

So I returned to the ranger station, and the starting pattern of unusual battery charging continues each morning.

Are the batteries ruined, or is there something else I ought to be considering?

Any advice would be appreciated.

[DmaxMaverick]

Your batteries are probably OK, for now. Too many deep discharges like that will kill them, though. Discharging an automotive starting battery below 10.5V is considered a "deep cycle", and these batteries are not designed for that service (that's what "deep cycle" batteries are for). It should hold out for more than a week. If you have no power using devices (ANY AT ALL) plugged/wired in, then you need to accommodate the condition, and count on it being dead after a week. I know, not a solution, but the reality. More expensive or higher capacity batteries would likely be just as dead under the same conditions. One solution would be to isolate your batteries so you don't leave both connected while the truck sits. You could disconnect both, if you don't mind resetting the clock. I've installed ground isolation switches on several trucks for just this purpose (the ground is easier because it's one wire per battery, vs. 2-4 for batt+). Any switch you use should be capable of handling 1,000 amps or more (careful not to save too much money on this item). Another possible solution may be a solar battery charger/conditioner for these extended periods. Don't go too cheap on these. The cheap solar chargers do fine during the day in full sunlight, but usually discharge at least as much in the absence of sunlight, and worse as the days are shorter than night. There are several kits available for your condition.

Your charging cycles sound absolutely normal for the conditions you describe. The voltage will always be lower immediately after a cold start, to provide additional power to the glow plugs and intake air heater.

[richp]

Hi DmaxMaverick,

Thanks for the quick reply. I think I know what caused the power drain on this occasion, and have remedied it. It was something that didn't matter much at home when I was using the truck every day, but when it wasn't charged up for a week or more, I guess even that small load drew things down a lot more than I estimated.

I was pretty worried about the charging pattern suggesting battery damage from this one incident. But in all fairness, I never paid the ammeter much attention until I had this problem, so it's good to hear that what I'm seeing is normal.

Best to you.

[NutNbutGMC]

Hi DmaxMaverick,

Thanks for the quick reply. I think I know what caused the power drain on this occasion, and have remedied it. It was something that didn't matter much at home when I was using the truck every day, but when it wasn't charged up for a week or more, I guess even that small load drew things down a lot more than I estimated.

I was pretty worried about the charging pattern suggesting battery damage from this one incident. But in all fairness, I never paid the ammeter much attention until I had this problem, so it's good to hear that what I'm seeing is normal.

Best to you.

http://www.batterymart.com/p-del-021-0128.html




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[trailrider0493]

I had this same thing happen on my 01 D/A truck. It turned out to be a stuck relay in the a/c unit. No trouble until the other day when my 7 year batteries went bad after 8 years.

[Mark Rinker]

http://cgi.ebay.com/ebaymotors/vw-volkswagen-solar-battery-charger_W0QQcmdZViewItemQQhashZitem35a4f8bcf9QQite mZ230401031417QQptZLHQ5fDefaultDomainQ5f100

These work - every VW comes with one, they sell cheap on Ebay all the time.