Sorry, but this post is a bit lengthy...

I picked up a 2007 H2 last summer, and the dealer had replaced the battery right before the sale. The battery completely died within 3 months. This first battery would not take a charge and was replaced under warranty. Got a brand new (second) battery, that died in about 2 months. It wouldn't take a charge on my charger and showed as sulfated, also according to my charger. The parts store was able to put a charge on it and lasted another month before it died again. I haven't tried to charge it yet this third time, but I figure it's about 50/50 that it will take a charge, at least on my charger at home.

As for a little background-The truck did have a Clifford aftermarket alarm installed when I bought it, but I had it professionally removed by a reputable alarm shop. However, I guess the alarm wasn't the culprit. I also noticed evidence that the PO had installed a battery tender directly to the battery terminals, so I am thinking that this could have been an issue in the past? Also, I only drive the truck every week or two, but I don't think that should be enough time to drain a battery under normal circumstances.

One other thing I notice about this truck. It seems to have a very slight leak in the rear air suspension, and the rear will (sometimes but not always) sag a bit after not being driven for a week or so. Could the compressor be kicking on to level the vehicle, or does the vehicle need to be started for that to occur?
I am starting to wonder if that could be the reason for the drain?

I would appreciate all thoughts on this! Thanks!

 

Do a search on parasitic battery drains. I think this will help.

 

My nickles worth of stuff would have the alternator checked. It could be going bad but slowly and sometimes charge but most the time not at the a charge level to keep the battery in good charge condition. Obviously the previous owner had this problem if he put that minder on the battery.

Could also be the wire from alternator to battery suffers internal high resistance and voltage drops every now and then. Or battery clamps or alternator ground to motor problem. This is just a maybe so no one attack me for writing it. Maybe at idle the alternator reads normal but driving speed it falls off and your using the battery more than it getting charged but enough charge to not go dead. That would cause a sulfated condition over a period.

When you pull a battery cable off the battery is there sparks when you touch the cable back to the battery? Put a digital charge meter on the battery back to the cabin and see what it tells you when driving.

 

Thanks for the input! I will check the alternator out. When I touched the battery cable back to battery, I did not notice a spark.

 

What year is your truck? If its an early model with the single stage rear suspension compressor there is programming updates for compressor cycling with ign off. If it has the dual stage compressor they are not programmable even though it can be programmed. Don't do it as it will lock up the module.

 

Never mind, re read your post, doesn't apply, sorry

 

Make sure when you turn the key to the off position the little red battery light goes off. I fought a draining battery off and on with my 03 and it was a worn ign switch that was not turning off everything. If you see the little red battery light on when you exit the vehicle, you WILL have a dead battery. A new switch fixed mine. Not the key portion, the electrical portion of the switch.

 

I don't see the red battery light. All lights seems to be off when the ignition is off. I'll have to double check-with my luck the bulb is burnt out in the battery light! LOL!

 

Well, I just reconnected battery positive side first, and did get a spark when connecting negative. Normally I do the reverse, but I wasn't thinking.

 

To help here, does anyone have a definitive answer as to what the stand-by current should be?

I checked mine and after a few minutes it dropped to 130mA but I suspect that it goes lower than that as the battery is fine, I read somewhere to wait for 15 mins

For a H2, with no aftermarket accessories etc, 25 to 40mA would seem about the right value, can anyone confirm this?