Changing Out BMW E36 Trunk Battery

How to jumper out the old BMW battery in your E36, and then install a new battery without erasing the ECU memory and radio code.

I have a 1998 BMW 328i, 4 Door, E36 wth a battery that began dieing (not able to crank engine) in cold weather. This battery lasted a total of 7 years, which is not bad considering most batteries die within 3 to 5 years (regardless of the 10-year warranty). I shopped around, but a lot of the Optima jell type batteries are too tall (causes the battery cover to protrude out and prevents the lugs from reaching the posts). I decided to bite the bullet and get the OEM BMW Group 92 battery (Douglas battery, 75 AH, 650 CCA). I purchased the battery from SavageBMW of Ontario, CA for $150.00 (I know, I got raped). The new battery, apparently, due to industry re-testing is now rated at 65 AH, 550 CCA at 32 deg F (I am still questioning this, since the new battery has decreased in length, which means Douglas either made the plates closer together, which is unlikely, or there are fewer plates...which means less plate surface area and less charege and Amp-Hrs. I bought the battery anyway, despite this, since it is hard to find Group 92 batteries in the normal chain of retail stores, i.e. Autozone.

Since removing the battery from your BMW will cause a radio code and ECU reset, I figured I could jumper around this...which worked 100%. Here is the procedure I followed:

Tools needed: 2 sets of jumper cables (8 or 10 AWG), BMW stock wrench and screw driver, socket wrench and fittings, and a brand new BMW BCI Group 92 battery.

Total time required: 30 minutes to 1 hour, depending on speed and skill level.

1. Open up battery cover, located on the right side of the trunk, and remove the plastic srew and nuts holding it in place.

2. Remove the battery bracket holder, located on the negative side of the battery, using the socket wrench and fitting.

3. Take the new BMW battery and connect the negative end of jumper cable from the negative post of the new battery to the negative end of the battery ground (preferably on the nut bolted onto the chassis).

4. Connect the postive end of the jumper cable from the positive end of the new battery to the postive end of the edge of the lug of the old battery.

5. Loosen the nuts holding the negative and postive lugs on the old battery and remove the negative, then postive lugs. (make sure the postive end of the jumper cable and lug does not touch the chassis by placing it on top of a piece of cardboard.

6. Next, remove the black air-breather tube, located on the postive end of the top edge of the battery.

7. Pull the old battery out, and then bring it to the front of the car. Open the hood and the postive connector cover. Jumper the old battery onto the negative and postive posts located on the upper front left side of the engine bay.

8. Take the new battery, bolt is it place, and then bolt the negative and postive lugs in place. (make sure that the battery is flushed with upper right hand corner of the battery housing so that the battery cover can be placed back over it when finished.

9. Remove the old battery from the engine bay by removing the negative and then postive jumper ends...then place the postive post cover back onto the postive post.

10. Close up the battery tray in the trunk after securing the battery in place.

11. Put the key in the ignition, start the car, and let it run idle for 15 - 30 min to allow the alternator to charge the battery (the battery already comes charged 95% - 100% capacity from BMW). You may also drive the car around. Note, that there should be no radio code errors...as with what I experienced, if the steps were followed properly. Savage BMW quoted me $369.00 total for installation and the cost of the new battery. I saved $219.00 in labor (which I can use to buy some after marked parts).

Enjoy!

James Alaoen

My 98 328 does not have a radio code -specifically says so in my owners manual. I disconnected it the other day to work on my instrument cluster (it is recommended you disconnect battery when removing airbag) and no probs.

whats the power cable's AWG on 6cilinder e36s?
maybe someone knows a good battery terminal for it and an audio amp? =)

Cool little DIY,

Not to shoot you down, only to add to what you've written,

I work at Battery World, a shop dedicated to selling only batteries - and have been there over 3 years.

Optima's are an Absorbed Glass Matt (AGM) battery - not gel. Gel batteries are no good at starting cars, where as AGM are ideal. BUT Agm cost alot.
A very good cheaper alternative to the optima battery is a Silver-Calcium battery (not calcium-calcium), such as Bosch or Varta.

The other part is that no shop should charge you for battery installation. We do it for free, and even for really difficult cars we only charge around $10.
Our cars should not need a radio code - i've done plenty and never been asked. It never hurts tho to run the backup power to save all your radio settings and wicked-rad equalizer curves.

good writeup man,

any questions, pm me

the other part i forgot to add is that yes, you should have the Din65 sized battery. These are called a din65 because in older days they were 65a/h. In reality, you are not after amp hours, but instead CCA (cold cranking amps). The reason your new one may have been shorter is that larger sizes will also fit inside the car. In mine I run a din75, so the last owner may have upgraded also.

The PO of my car put a normal battery in

I might be upgrading to a yellow top optima

I believe that you can also plug a battery tender into the cigarette lighter when changing the battery and it will supply enough juice to keep from losing ECU settings, radio codes etc.

Originally Posted by TnT817

The PO of my car put a normal battery in

I might be upgrading to a yellow top optima

What's the difference between the blue and yellow top?

Originally Posted by Skillet77

What's the difference between the blue and yellow top?

blue top recommended for marine, red top for tough starts, yellow top for systems and high output and such. i have a yellow top in mine. love it with all my heart
and i got it cheap since we sell them at my job

Originally Posted by Daddyt06

blue top recommended for marine, red top for tough starts, yellow top for systems and high output and such. i have a yellow top in mine. love it with all my heart
and i got it cheap since we sell them at my job

well I can't pay 200 bucks for it.

Originally Posted by Daddyt06

blue top recommended for marine, red top for tough starts, yellow top for systems and high output and such. i have a yellow top in mine. love it with all my heart
and i got it cheap since we sell them at my job

Could you get me one cheap

I work at best buy and could return the favor

the absolute only difference between the blue and the yellow is the extra accesory terminals. This is the ONLY difference.
there is however different colored greys in each. The dark gray cases are for deep cycle, and the lighter grey are for starting.

I just glued about 47 Duracell 9-volts together and it's been working out pretty well for me.

What size Optima are you using? Does the battery cover still fit?

Not on mine. I think mine is a 900 cca and the cover sits about 1.5 - 2 inches higher than normal. It still fits "in" the opening, but you need to but like a "shim" to keep it level so it doesnt fall off.