They are usually readily available. Be sure to pull any vent hoses off at the battery connection before you lift the old battery out. Mine had a vent on the passenger side which I broke off where it goes through the floor. Don’t make my mistake.

 

Probably a Group 78 with close to 800 CCA.

Vented battery - hose goes through floor pan.

p.s. - the original battery may have been a Group 79 (like mine) but they're as scarce as hen's teeth now. Only differences are a slightly larger case for the 79 and maybe round vent connectors for the 78.

 

The vent battery is a little more money but you need the battery vented. I saw a DTS with a non vented battery inside the car it's not worth saving the small amount and endanger yourself and passengers.

 

.......... and a non-vented battery WILL cause extensive under-seat corrosion in short order.

 

It's an H8.

 

I took out the back seat today to check what was in there. It's an AC Delco #94RAGM. I saw 1 hose on the passenger side of the battery and it was loose with a broken connection on the end of it. Looks like whoever replaced it last time broke it as mentioned above. I'll have to figure out where it goes to reconnect it. No issues though, looks good under there. Are all vented batteries AGM's?

 

No, and the 2008 uses the wrong charging and voltage protocol for an AGM battery.

You need to find what type and number of battery was installed as original - flooded lead-acid, gel, and AGM are all different batteries with different charging/voltage specs. Some are vented, some are not.

My "vented" post assumed a flooded lead-acid battery with vents - they must have the tube(s) attached and routed outside the body.

 

You need to find what type and number of battery was installed as original

Other than trusting the parts store, is there a way to tell which battery was originally installed by any of the numbers on the back side of my trunk cover?

 

If I'm understanding the Delco correctly (94R "AGM") then I guess the wrong type battery is in there now?

 

Group Size H6 externally vented

 

In 2008 or 2009, the DTS switched from a Side post battery (Group 79) to a Top post battery (Group 94/H7)

You can always replace the vent hose.

Also when you buy a new 94 battery, the terminal protector plastic comes with a plug for the other side of the battery

https://a.co/d/iJjhnVk

 

I just looked through my costco receipts. You are right, it was an H7 that was installed in my 2008.

 

Good to know when the type change went into effect.

 

According to gmpartsonline.net this is the type of battery that was used in 2008. However, it also says this product has been discontinued. (FYI: My 2007 DTS battery is a vented side-post model: 79PG)

 

According to gmpartsonline.net this is the type of battery that was used in 2008. However, it also says this product has been discontinued. (FYI: My 2007 DTS battery is a vented side-post model: 79PG) View attachment 627869

In the meantime, I also went to the AC Delco online site and they also stated that the 88865934, like you have posted, was the correct one for my car. I then called my local Chevy Dealer, who also sells Cadillac parts, and they have one in stock. I believe he already did, but I will verify the application when I get there.

 

Appreciate all the replies.

What is in there now is a 94RAGM (88864542) Top Post Side Vent.

Wrong battery all this time? (since last replacement)

 

94R ? Did they replaced your battery cables to make it fit? The OEM 79PG uses screw-in terminals located on the front and has vents on the side.
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What the heck - if the voltages look good, the car starts easily and runs right - don't sweat it.

Just for grins one lazy day - get in, stick the key in the ignition (or whatever it takes) and call up Voltage in the DIC.

Post the Engine Off voltage, normal idle voltage, cruise voltage, voltage with A/C and headlamps on.

In order - 12.4 to 12.6,............ ...13.8 - 14.2, ................14.0 - 14.8,.................. 13.8 - 14.6.

Although an AGM uses a different charging/maintenance electrical protocol the car's system may be "smart" enough to compensate for differences. As always, If it ain't broke, don't fix it.

 

Appreciate the info. Strange as I searched around at O'Reilly's, Advance, AutoZone and Wal-Mart and 3 of them had an application that stated an "AGM" was correct for my car.

By the way, what type of battery is the 88865934 94R/PG?