Batteries Dying

[gimpyhauler]

Something is dragging my batteries down. I had them tested recently and they tested good under load test.

It takes a matter of days to get to where I don't have enough power to turn it over.

Anyone with an idea of where I should look first? Nothing I've added to cause this.

[DmaxMaverick]

First, make SURE you aren't leaving any accessory connected when it sets. If you have any aftermarket electronics added, they would be the first suspects. Also, phone chargers (and the like), even with no phone/device connected, WILL draw power. Once you've eliminated this as a possible cause, read on:

You probably have one failing battery, despite your load test results (they are rarely accurate). If the truck sets for days at a time, use two of these episodes of this to test each battery, individually. This is a good time of year for the test, needing less power for starting, compared to cold winter.

Charge batteries fully, either by driving or charger. When you are ready for it to set for a period, disconnect the passenger side battery (ground terminal only). After a day or two, try to start it. If it's dead, disconnect it and connect the other. The engine should start (it should do fine with one good battery). If it doesn't start, the passenger battery is bad (the usual suspect). If it does start, reconnect both batteries and fully charge. Repeat the same test with the driver side battery disconnected, and the same time period. If the second time it doesn't start, but does once the driver side battery is connected, the passenger side battery is bad.

If the test results in both batteries failing, you may have a real gremlin stealing power. Now the fun begins. Isolating the system can be a long, difficult process.

2001-2002 trucks should last a month or more with good batteries, and still start well. 2003-2005 a little less, and 2006+ less yet. The electronic "stand by" power requirements increase with technology changes (more gizmos and gadgets).

Don't rely on volt meter or load tests after they aren't used for a day or more. They will lie to you, with superficial high voltage readings and load results. Having two batteries connected parallel with one bad battery will discharge both batteries much faster/deeper than one bad battery by itself.

[gimpyhauler]

DmaxMaverick,

> Charge batteries fully, either by driving or charger.

Charged them for the last 24 hours. Both showed fully charged.

> When you are ready for it to set for a period, disconnect the passenger side battery (ground terminal only). After a day or two, try to start it.

I tried it after disconnecting the charger. I disconnected the passenger side, it wouldn't start. I re-attached the passenger side battery and it still wouldn't start.

I drive an '07 Classic. 165,000 miles. They are replacement batteries but have no idea how old. I'm thinking it's time to replace both batteries before I take it to the mechanic to diagnose the problem I'm fairly confident I figured out with your helpful instructions.

Any suggestion on brand of batteries? Are the six packs (Optima) worth the money? Interstate, which ones?

However, my truck may sit for a month or more at a time. Should I keep it plugged in with a battery tender or is there another option?

I appreciate this help. :cool:

[DmaxMaverick]

I'm not sure anymore about the battery brands. Optima used to be a premium, and I used/use them. Quality isn't what it used to be, and the price went through the roof, so I don't know. At this time, I'd have to default to the AC Delco batteries. They've seemed to be the most consistent of the bunch. The commercial/industrial line are more durable, but cost more.

If you are leaving your truck unused for a month or more at a time, I suggest disconnecting the batteries, and perhaps removing them from the truck for longer periods (if it isn't too inconvenient). Unless you have a need for the truck to remain continually powered, "tending" batteries usually proves to be counterproductive. A fully charged battery should remain sufficiently charged for several months, if it's healthy and clean (dirty tops will discharge them), and disconnected.

[gimpyhauler]

DmaxMaverick,

> If you are leaving your truck unused for a month or more at a time, I suggest disconnecting the batteries, and perhaps removing them from the truck for longer periods (if it isn't too inconvenient).

As an old man with bad shoulders, removing them isn't an option. I'm sure it'd be a good thing to make sure I start it and drive it even short distances once per week.

> Unless you have a need for the truck to remain continually powered, "tending" batteries usually proves to be counterproductive.

I do have a premium tender. I ought to use it if I'm not going to drive it regularly.

Called a friend with my truck with a short bed. He just uses the Bosch premium batteries from Pep Boys (Manny, Moe and Jack). I just went out after two days and it started fine. If they were the prior batteries, I'da had to jump it.

I appreciate your help very much. This is a great place with great people to find help.

[JohnC]

I'm sure it'd be a good thing to make sure I start it and drive it even short distances once per week.

I strongly recommend against this. All it will do is get the oil permeated with water vapor, which combines with the combustion byproducts to form acids. These, in turn, promote corrosion throughout the engine. If you can't drive it long enough to get it up to operating temperature and keep it there for a half-hour or so, you're better off not touching it. IMHO...

[DmaxMaverick]

I strongly recommend against this. All it will do is get the oil permeated with water vapor, which combines with the combustion byproducts to form acids. These, in turn, promote corrosion throughout the engine. If you can't drive it long enough to get it up to operating temperature and keep it there for a half-hour or so, you're better off not touching it. IMHO...

I agree, absolutely.

[More Power]

My Lil Red project Duramax has sat for months, and still started without touching the batteries. This is a 2001/02 engine and electronic system. It does take about 4-5 months of sitting unattended before it cranks noticeably slower. A couple of years ago I began using a battery tender at least once a month when it sits through the winter, just to keep them fully charged.

My 2001 GMC 2500HD (bought in December 2000) still has the original ACDelco batteries - still cranks fine, even through this past cold winter. It seems those truck owners who live in the warmer areas of the country see shorter battery life. So, it seems heat is more of a battery life problem than either cold or time. For myself, I'm sticking with ACDelco.... ;)

It sounds as though your truck has a battery drain problem. Remove one of the negative battery terminals, then measure battey drain on the other battery (use an ammeter between the negative battery terminal and the negative battery cable). Once you know whether there is a significant battery drain (there will be a small drain - that's normal), you can pull fuses to see what circuit is causing the biggest drain in the electrical system.

Jim