I have a Chevy Silverado 2005 1500 hybrid. I suffered the same problem as jmarshall. I was driving home and everything shut down. No brakes and no steering. I almost went the someone's fence. This is so dangerous. I towed it to my mechanic who tried to fix it to no avail. He said the regular battery kept frying. He suggested I take it to the dealer. I absolutely hate the dealer nearest to me. He has absolutely taken advantage of me in the past so I preceded to look for another mechanic in town. I found someone who was sure he could fix it. Had my son talk to him also because I am an older woman and didn't want to get taken advantage of. He said the hybrid batteries are shot. He called Chevy Corp and found out they quite making the batteries. We have called salvage yards, ebay and about 20 places that sell hybrid batteries. to no avail. Now I have a truck that in excellent shape with only 136,000 miles that won't run. As far as I can find out it might have to be a part truck. This seems so unfair that I can't get a battery. Does anyone have a suggestion?

 

so I have seen a few questions about these and finally read a bit. so this "hybrid" seems to have all of the down sides of relying on it's extra batteries for cranking the engine, steering and brake booster. but not much upside in fuel mileage because no power goes to the wheels.

anyways, what I see is your have 3 lead acid batteries under the back seat somewhere used as hybrid batteries. these are made by Panasonic # looks like HV1255.

if you Google that you'll find listings but all are European. it also says it's a VRLA valve regulated lead acid battery.




https://na.industrial.panasonic.com/...lead-acid-vrla

I'd email Panasonic industry and see what they say.



so I kinda went thru this VRLA battery crap at work this last season. we got a new deice truck built in Europe shipped in, supposedly this was shipped to Denmark as their test bed for using US based chassis instead of their normal Volvo's. so long story short turns out the 2 batterys used to run the 24v side of things had gotten very weak and couldn't hold a load. most likely from sitting around for 2 years dealing with customs and getting into and out ports. we just got "lucky" by getting the test bed. it had tons of other issues too, but the batteries called out were a AGM VRLA. well we Googled and nothing local but seemed common on European websites. so after talking to the company, they told us all agm batteries have to be internally valve regulated. they are sealed and have a valve that can pop open to vent if they overheat before they explode or something.
just Europe seems to use the term and we don't. so we speced out the physical size and the amp hour ratings of the 2 12v batteries local to us, tossed them in and worked fine and they credited us the cost under warranty. saved them shipping from Denmark to the US for the same battery type with different branding.

I can't really find any spec of these HV1255 batteries. but if you do and can get the same type of battery, such as flooded acid or agm, with the same amp hour rating. my 2 cents before scrapping the truck as a parts truck would be to install them, use a gm scanner to do their procedure for replacing the batteries and go.

according to what I have it says Panasonic battery are designed to have a life span of 36000 amp hours and if all 3 batteries are replaced you need to reset that to 0 in the battery electronics control module. plus looks like all 3 need to be charged to 100% before install, because the ecm only uses 50% of the state of charge and it needs to know what 100% is to do its math.

I'd check with Panasonic first and hope they have info, but I have a feeling theses aren't all that special of a battery, a replacement might have a little shorter life but looks like it's supposed to throw a check engine code if there's a battery pack issue before it just gives out and you loose Assistance.

just my thoughts. I don't have any experience with these older trucks at all. but seems a shame to scrap a truck over 3 12v lead acid batteries.

 

wouldn't it be a better idea to jjust replace the SLA batteries with a capacitor bank instead? which have pretty much an unlimited life cycle

you can find VRLA batteries at a place that sells fork lift batteries modding might be required..