DIY: Installing a group 34 battery

[FiveOhJoe]

My battery was on its way our but I did not want to install another stock-style battery. Optima was a great battery, but not anymore so that was out of the question. After a ton of research, I settled on an AGM(Absorbed Glass Mat) battery. These batteries are the real deal, they can take a ton of abuse, they don’t leak, don’t require maintenance, and they produce a lot of power for their size. Ener-Sys Odyssey is the leader in this type of battery, and you can get their group 34 battery for about $300, or just do what I did and buy a Die Hard Platinum, which is just a re-labeled Odyssey battery. There is nothing different between the two, it’s literally just re-branded.
The closest battery size to the stocker is the group 34, it’s just a little longer and a little taller, thus it’s not just a drop-in replacement. I got mine during one of Sears’ friends & family nights so I got 10% off. Expect to pay $200-240 for one of these, depending on your area.
Here are some quick specs:
Type: 6-cell Depp-Cycle Absorbed Glass Mat
Size: 7.8” tall // 10.9” long // 6.8” wide
Weight: 53lb
CCA: 850
Warranty: 48 month free replacement – then another 52 months pro-rated from day 1.

Here is a link to the battery I used: DieHard Platinum 34 : Exclusive Maintenance-Free Batteries at Sears

Start by removing your old battery. Mine is an EverStart. Use a ½” wrench to loosen the clamps on the terminals, ground first, then positive. Then look on the passenger side of the battery, you will see the hold-down clamp. Remove the bolt with an 8mm socket and set the bracket to the side. Then lift the battery up out of the car.
You can see now the size difference between the stock sized battery and the Die Hard group 34.

Now we need to remove the battery tray from the car so we can modify it to fit the new battery. Using an 8mm socket, remove the 3 bolts holding it in. One on the bottom, and two holding it to the side of the engine bay.

With the battery tray out of the car, you can see that the new battery is about 1 inch too long. We need to remove the side wall of the battery tray. You can’t remove the front wall because the battery will hit the headlight area, so we have to remove the back wall. You can use whatever you want to cut it. I used a Dremel with a Plastic cut-off blade. It went through it like butter.

Now with the wall removed, the battery can sit in the tray nice and flat, only sticking out maybe ¾”.

I thought I was done, but unfortunately the 3 series battery is about 1/3” more narrow than the stocker so the battery clamp doesn’t even touch the battery. There is not enough give in the bracket to take up the slack. The ridge that the clamp clamps down on is also lower on the new battery, so even if you could just slide the clamp over, it wouldn’t clamp down on the battery properly.

The first thing I did was shorten the clamp. Use your cut off wheel or a hack saw to cut the bracket down to roughly 28-30mm

So now the clamp touches the battery how it should. However there’s not a snowballs chance in hell that the bolt is going to thread in. You can’t just open up the hole either, the plastic would probably break when you tighten the bolt.

What I decided to do was get rid of the OEM bolt and just make my own stud and nut setup. I used a 5/16 x 2 ½ bolt. All I had laying around was this button head bolt, you should use a hex head!!. Then there is a nut that will hold the stud in, then the bracket goes on, then another nut to hold that down.

First we have to drill a hole in the stock battery tray for the new stud. But first you have to get rid of the metal bracket on the bottom side of the tray. Use a cut off wheel to get rid of the melted plastic nubs holding it on, then it will just pry right off.

In this picture you can see my hole for the stud. I suggest drilling this hole with the bracket and the battery all mounted where they need to go, then just drill a 5/16” hole through the braket where you need your stud to end up. Hard to explain that part, sorry.

This is what it looks like with the bracket removed. I also sanded down those two parallel plastic protrusions, they were in the way. The new hole is the one on the top of the picture.

Now stick the stud up through the new hole. Put a nut on it with some red loc-tite and tighten it down. You could use a washer if you want, but it’s not necessary, since the load will be pulling the bolt UP

Now you can test-fit your hold down clamp. You will see that you need to cut out some plastic to clear the nut. Make it so it the clamp can sit flush on the battery tray like in the picture below. In the picture below you can also see the washer and nut I am going to use to clamp it down. I swapped out that knurled nut for a regular nylon locking nut
Before clearancing the bracket:

After, with everything mocked up:

Now test fit everything with your battery. Make sure everything is nice and snug.

If all is good, then you can re-install the battery tray and drop in the battery, then clamp it down! Then re-connect everything. Positive first, then negative
Tray installed:

The battery clears everything fine.

The extra height is a non-issue

 

[Fastphil]

Fantastic, just what I was looking for. I'm shopping for a new battery as my Optima Red Top 34/78 bit the dust. I don't want to go back to a Group 59 either. I'm wondering if there's some way to use the Optima's adapter bracket to avoid all the modifications you've made. Thanks for the write-up!

 

[SVTORANGE]

Excellent detail information - Nicely done

 

[Fastphil]

I just ordered an Exide Group 34 AGM battery (quite a bit cheaper than other brands with similar specs), so I'll be putting this thread to good use within the next week.

 

[Fastphil]

I just installed my Exide Group 34. I had to modify the battery tray like you did, but I was able to modify the adapter brackets that were on my Optima battery. I ground them to shape to fit the lips on the sides of the new battery, and I was then able to use the factory bolt and hold-down wedge in the factory location. Thanks for the post, it was useful!