Battery Drain Article
Starter Info
Electrical Info

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How Long Do Batteries Last

Had a friend who worked in the GM battery plant in Indiana (now closed). He said that their knowledge of battery technology was such that on a battery with a 36 month warranty, about 50% would fail within the warranty period but 70% would fail within the next few months following the expiration of the warranty. Stated another way, on a battery with a 36 month warranty 70% would fail within 48 months. It's amazing to me that they could control it that closely.

Anyway, I have gone to replacing my batteries every 3 to 4 years. The old Optima's used to be great, but since they were bought out and commercialized a few years back it seems that they are really no better than any other good quality battery.

One of the major causes of battery failure comes from low charge usually due to short distance driving.. If you don't drive your truck often and far enough the battery never reaches a full charge. This causes acid stratification and sulfation which degrades the battery.

Hummer Batteries and Hold Down Clamps

The correct batteries for a diesel Hummer are Group 78 which has side terminals. The batteries should have 800 cold cranking amps (CCA) and 1000 Cranking Amps. I presently have AC Delco 787YR batteries in my truck. They measure 10.25" long, 6.75" wide and 7.5" high. It looks like you could go up to about 7" wide. Size matters because the battery tray in the Hummer is molded to size. Note: Group 34 Batteries have Top Post terminals. You could use group 34/78 which has top and side posts. You just have to modify the hold down clamp.

Interstate has a MTP-78 That fits.

EverStart Maxx

According to Consumer Reports Oct 2006 the Group 34/78 Everstart MAAX-1N Battery sold by Walmart is the best group 34/78 battery you can buy. I bought 2 in October 2006 for 78.00 each. They are warranted for 3 years replacement. The batteries have a built in handle which is a nice feature. The batteries have 1000 Cranking amps and 875 Cold Cranking Amps (CCA). The battery has top and side terminals thus the 34/78 designation. Note: The battery Walmart lists for the Hummer does not have the same capacity and does not meet the above power specs, although it doesn't have top terminals.

The battery is not a sealed maintenance free battery. That means you will have to check the water level from time to time and fill the cells with distilled water. It also means that your top hold down bracket will not fit over the top terminals.

New Maxx BatteriesI've had the above Everstart batteries in my truck for 2- 1/2 years now and one or both have bit the dust. One day the truck wouldn't crank. The batteries measured 5.5 volts. I charged them up overnight to 12.5 and the truck started. The alternator was putting out 14.5 volts so it was working fine. I shut the truck down and left it sit over night. The next morning the batteries were down to 10.5 volts. The nice thing was I walked into Walmart with the 2 batteries and walked out with 2 new one's for free; no questions asked. The new ones read 12.82 volts. This time I got the Maxx battery without the top terminals. They do not have the same cranking amps but they don't have the top terminals. Even though my bracktet avoided the top terminals I was always worried that they could short out. We'll see how it works. So far the truck starts.

Rusted out battery tray Refurbished Battery Tray

When I pulled out my old batteries I was facing a completely rusted out battery tray. I chipped away the rust and wire wheeled the surface. I painted the tray with 'Rust Bullit'.

I used a hole saw and cut 4, 1-3/8" diameter holes in the bracket. Another problem is that the molded hinges for the carrying handles stick up and keep the hold down bracket from sitting flat on the battery. You can take the handles off and trim the plastic flat with a razor blade or simply glue some rubber to the bottom of the bracket allowing for the bumps in the handle.

An Alternate Battery Hold Down Clamp

by Keith Perry

I also trimmed my battery hold down bracket to allow for the top posts on my Optima Batteries. I don't like the drilled holes because somebody is inevitably going to attach jumper cables to those top posts causing a short on the bracket. I just cut my stock hold down bracket skinnier across the top. It is a heavy duty bracket with two side and center bolts to hold it. Even at half width, it is strong enough to hold them down.

Note.... Do not run your truck without the hold down bracket in place or you will put holes in your hood from the top posts or battery corners when you hit a bump and the batteries go flying aside from ruining the batteries.

Battery Bracket

While hooking up a new battery I got a big spark when I attached the positive wire.

You shouldn't have a big spark. That indicates a short or a large parasitic drain.

As you touch the wires to the posts you will get a little spark that will stop once the connection is secure. If the battery cables get warm after you connect them you have a major short - immediatly disconnect the battery cables from the truck and fix the short. A short large enough to warm the battery cables could cause major damage and possibly start a fire.

Read the parasitic drain article

I pressure washed the truck, saw a big spark and now it won't start.

First: check to make sure the battery terminals are firmly connected to the battery. Check that the ground wire is firmly bolted to the grounding point on the engine. Check the red hot wire for a good connection at the starter.

Next, in order:

Start testing for voltage from the battery. Use the chassis ground (engine block is fine, but not the battery ground)

Have 12V at battery terminal? No=bad terminal connection. Bad ground (retest the ground)

Yes? Test for 12V at the starter main battery terminal (big wire). No voltage? Bad battery cable.

Yes? Test for 12V at the glow plug controller. No voltage? Bad fusible link at the battery terminal.

Yes? Test for 12V at the power distribution block (driver's side wheel well (engine side). No: bad fusible link at glow plug controller, or connection.

Yes? Test for 12V at the fuse block? No: bad fusible link at the distribution block.

This is not an exhaustive set of tests, but will get you started. I suspect you blew the main fusible link at the battery terminal. DO NOT REPLACE THIS WITH PLAIN WIRE, EVEN TO TEST! You *must* if this fusible link blows, replace it with the correct fusible link wire, in the correct size.

The ground to the engine was bad and the insulation, about three inches at the starter terminal end was melted.

I Turn the Key but the Engine won't Start and the Starter won't Turn.


My New Batteries Died within Weeks


Testing Batteries

My truck wasn't starting like it used to. It was getting sluggish.

First do a 'load test' where they just attach alligator clips to the +/- and watch the voltage drop as load is applied. Because the diesel Hummers have 2 batteries you must separate them and test each battery on it's own.

Then run a deep cell test. For this you have to physically remove the batteries from the truck and place them in a machine, which comes complete with safety screens.

Battery Energizers

These are for real. Here's what solargiser which is used by the military says.

The main cause of battery problems and failure is sulfation buildup (sulfur deposits on the lead battery plates). This can be relieved with the use of the PulseTech Solargizer.  Pulse technology is defined by a distinct, patented "pulse waveform". No other battery maintenance system in the world has this specific waveform which means No other system can provide the same exceptional benefits as PulseTech battery maintenance systems. This technology completely eliminates the sulfation buildup by removing the sulfate deposits from the plates and returning them to the battery acid as active electrolyte.  With the plates clean the battery will perform at peak efficiency and battery life is extended dramatically.

Solargizer is not a charger, the power it produces is to maintain the operation of the solargizer only. The solargizer is a solar-powered device that maintains and improves lead-acid batteries. By ensuring peak battery performance, reducing downtime, and increasing battery life dramatically. The Solargizer provides greater charge acceptance enabling a battery to recharge faster and with better quality.  It even prevents the normal loss of battery power on stored vehicles - no matter how long they sit unused! The Solargizer (except multi-wire units) can also be ordered with a specially designed AC adapter for use on vehicles stored in areas without sunlight. They make a device called Power Pulse which is powered by the actual battery. This would be good for trucks that are parked in a garage out of the sun.

Another is made by Canadus and sold through Peterbuilt dealers.

Optima Batteries

Optima's engineers were recommending to AM General's engineers the use of Optima "Red Tops" for the HUMMER (H1).  The 34/78 and 75/25 both have dual setups with posts on the top and GM Side terminals. You need side posts for your H1.

Just to put some numbers to this.  In the 34/78 popular size Optima the Red Top is 800 CCA and the Yellow Top is 750 CCA.  Both do fine as a starter battery. Especially so in the Hummer since there are 2 of them in parallel 1600 CCA vs. 1500 CCA total. The difference should not ever be a problem except in those marginal starting situations that can come up.  The Red Tops will die much sooner according to Optima if deep cycled which is the case with some vehicles running inverters, winches, etc and not having the motor running all the time. This has been found to be true in actual experience. Only a few deep cycles can kill the Red Top or any other non deep cycle regular battery. They can not take the deep cycling, and still start the truck like the Yellow Top. The Yellow Tops are designed to perform in Deep Cycle service up to 300 times as well as serve as a starter.  I have found the Yellow Tops to last about twice as long in my truck as the Red Tops which I tried.  If you have a box stock Hummer that will not have any significant loads for extended periods with the engine not running  (the case AMG Engineers are considering) then the Red Tops will be fine.  Your mileage of course may vary.

Do not use the Optima side terminals if you intend to attach an electric winch to it. I spoke with an Interstate engineer and he stated they will not warranty a DT battery for winch use. It appears that the top post is the main connector to the cells and the Optima uses a relatively thin connector strip from the top post to the side terminal connection. This strip will melt kind of like a fuse or fusible link under winching loads. Hummer owners have reported if you have an electric winch use the Yellow top deep cycle batteries.