Any BMW 335i owners replace your own battery?

[Paul A.]

I have a 2007 E92 and suspect my battery is giving up the ghost. This will be my 3rd battery and the second one was replced by my indy shop. I'm gonna try to DIY this one. I've been through a few You Tube vid's and it looks pretty simple but are there any "gotcha's" that BMW just loves to engineer into the DIY community for a trunk mounted battery?

Thanks in advance.

[Coleroad]

No straight forward. Just make sure you hook the vent tube back correctly so it vents out of the trunk. You need to program the new battery to the car so it charges correctly, or you'll shorten the life of it. You can use Carly for BMW to do that. Not sure what the app cost is for it now, but it's cheaper than having the dealer do it.

[usshelena725]

^ This. There are some pain in the bum issues with the battery due to the items attached to it for the programmable charging that goes on, but the physical part isn't that hard.

The main problem comes into play in that unlike most cars, you have to program the battery to the car. This requires your ability to code a BMW. If you don't have the ability to do coding or know someone with a KDAN cable that can do it remotely for you, then you are best taking to the dealer.

[WaxMaster1]

When I had my M235i I remember there was an entire rigmarole involved with replacing the battery. UGH!! I got rid of the car, problem solved.

[Coleroad]

It's not complicated, programming the new battery is easy. It's just telling the computer the mileage the new battery went in, and the specifications of the new battery. Takes just a couple of minutes to complete. The dealers make it sound like a big deal to justify the their price. They want you to bring it in because that's quick easy money for them. The only thing the dealer will do that you probably won't is they put a charger on it to save all your settings. You can do it if you want just be careful with your battery leads then.

[Paul A.]

Thank you, all, for chiming in!

Yes, I am aware of the battery registration after install and have a guy with a BT cable and software that"s gonna do it for a car wash. I also have the vent tube considered. Thanks Coleroad.

[oneheadlite]

Just take your time and keep an eye on how things were connected. Be sure not to torque around too much on the positive battery cable.

All you need to unbolt is the 10mm nut - leave the 13mm nut alone as I don't like shifting that connection. I disconnect the slide in connections (blue and silver paint marks) and tuck the wires out of the way to make life easier. I like to cut the zip tie for the interrupt ignitor (leave that yellow connector secured). Flat screwdriver to pop the silver retainer strap off the sides.

The negative cable has an "Intelligent Battery Sensor" that has a 2 wire lead that comes off it - make sure that gets plugged back in. There's a 2 or 3 pin connector in the body harness near it that's empty - that's how they are.

Other than that, just be sure to lift squarely so you don't KO your back! I've got a friend that wrecked himself by twisting while bent over taking a battery out.

Hope this helps - I've done a few dozen of those in my time. (BMW indy Tech)

[Paul A.]

Wow! THANK YOU so much oneheadlite!

[oneheadlite]

Also - What battery are you using? Do you do lots of short trips?

Three batteries in that time is kind of a lot. We do Interstates and genuine BMW here. The price difference is so small, and the genuine batteries have such a track record of going 7+ years, that's always how I lean. (The interstates have been fine in all honesty).

Make sure when the new battery is registered that it's registered as the correct amperage/type as well (IE: 90aH regular vs 92aH AGM/etc.).

If you ever have any questions on your car, feel free to ping me! Always glad to help!!!

[Paul A.]

I am going from a non AMG to an AMG type. H6 I think (hafta check). 900 CCA. Thanks again, I greatly appreciate your expertise and experience.

Yes, lots and lots of short trips, stopping and starting.

[oneheadlite]

I am going from a non AMG to an AMG type. H6 I think (hafta check). 900 CCA. Thanks again, I greatly appreciate your expertise and experience.

Yes, lots and lots of short trips, stopping and starting.

I like to stick with the interstate H8 / 90Ah batteries, even for cars that came with the smaller 80Ah.

I've heard theories both ways with the AGM (Absorbed Glass Matt - basically "gel cell") style batteries as far as if they help with short trip use. Can't hurt to try it if you've been going through the standard "flooded" batteries.

Definitely important the correct registration happens in the engine computer when you switch styles. The AGM requires a much more aggressive charge pattern compared to the regular batteries. This could stand to cook a regular battery registered as an AGM, or not sufficiently charge an AGM registered as a standard battery.

The lots of starts-and-stops isn't so much a problem as a generally short driving distance. But in my experience it usually takes many <5 mile trips to really cause issue for getting "Increased battery discharge" warnings or slow cranking.

I forget you're in Florida - Heat is a killer of batteries too.

[Paul A.]

Quick question...can i drive it a short distance without registerring it? I'll be relocating the car after install to get it programmed in.

[Paul A.]

Whoops, its not an AGM. Sorry. Maxx Everstart H8.

[oneheadlite]

Quick question...can i drive it a short distance without registerring it? I'll be relocating the car after install to get it programmed in.

For sure - short term is ok, but long term takes it's toll on the battery.

I would think that battery should work fine. Don't have much exposure to that brand.

[Paul A.]

Thanks again, brother.