2008 GMC Yukon hybrid(Dec/07production), 12V battery charge drops and not able to start the car if not driven or started in 48 hours. Nothing that looks obvious is turned on which might cause this to happen. At one time during the shipping of the vehical, the 12v battery was drained dead, for several days before was charged which may explain the short life cycle of the battery. I had a local shop test the battery, I am told the battery is bad.

My question, is the 12V Hybrid Electric Propulsion (HP2) battery same as regular battery? Anyone has replaced the 12V battery? If so, did you use a direct replacement or aftermarket?

 

It is just a Maintenance Free 12V battery as far as I know. You will need to match the CCA's and total capacity. My '09 Hybrid Silverado has an AC Delco 8542, 70 amp/hour with 730 Cold Cranking Amps. I am not sure what they mean when they say "maintenance free". It may be an AGM (absorbed glass mat), which is a great battery but more expensive. I would not put anything except a sealed battery in your truck. But any comparable will do. A malfunctioning 12V can cause some weird problems in a hybrid however. Wasn't there a recall on something related to the 12V battery in the early '08's?

 

"maintenance free" is a marketing term from the 1980s. This means you don't have to regularly top off the acid in the battery. They used to have screw tops, then with the "maintenance free" they switched to what looked like a sealed top, but they are just lids on the three-cells that are pried-off with a screwdriver. They can still be filled up just like the old batteries. For the most part, they are "maintenance free" because they don't need to be filled with normal use, BUT you can still check them out and fill them with distilled water, if needed.