A warning, for what it's worth, concerning the factory sealed batteries on the GM Duramax's.
I was at a drag boat event a few weeks ago and recieved a phone call from my wife informing me that the truck blew up in the bank parking lot. She said that there was a huge explosion when she attempted to start the truck and lots of smoke came out from under the hood; she also said that the bank security guard came running out, pistol in hand thinking there was an attempt to blow up the bank!
She went on that she opened the hood after an appropiate amount of time of quiet and no smoke and found that the battery blew up. I told her that I would be there as soon as possible but in the mean time if possible the acid needed to be washed down. That didn't fly so I knew I would have to hussle to limit the amount of damage being done by the acid. I made it in a little over an hour and found that there were no hose bibs on the bank so we went to the house an filled several coolers with water, stocked cleaning supplies and sped back to the bank. The entire top of the battery was blown off and came to rest over the turbo and the sides were partially blown out as well, quite an explosion. The amount of acid on things was not as bad as what I had expected. I cleaned as much as possible, removed what was left of the battery and cleaned some more. I think I was actually lucky as damage seem to be limited to paint discoloration under the hood and some pitting of the fuel filter housing and the AC lines; I guess time will tell if the damage grows any more.
The cause; there is no way of knowing for sure but my theory is this: You cannot tell what the acid level is in these sealed batteries so after so much time the acid level gets down to a point where plates and cross-over are exposed to a acid gas (explosive gas!). I think this is more common on the passenger side battery because of the high heat location of the battery placement, this is the one that blew up. The low acid level in this case is probably why there was less acid on things than what you would first think. The low acid level also increased the volumn of explosive gas and the reason that the explosion was so large. Now what set off the explosion; I think that the acid level got below the cell links and deteriorated one to the point that there was a near gap, so when she cranked the truck the high draw arched at the weak connection and boom the rest is history.

So how do you avoid this happening to you. A good question, In our case the truck showed no signs, what so ever, of weak batteries; always cranked over and started instantly. Interesting fact in our case is that before our last trip to Colorado a month ago I told the wife that the batteries were getting old enough that we ought to go ahead and replace them before they did go bad and that doing that before the trip would be a good idea. Intentions of course don't get things done.
Any suggestions other than gels or regular service batteries?

Randy