Aux Battery Replacement

[bavautosport]

After 8 years and 130k miles, the main battery finally gave up. I replaced it with the Duralast one from Autozone and registered via BimmerLink. My question is if it’s a good time to replace the aux battery as well? I’m not sure which signs to look for, or how to check its health? And yes, I did my homework both in and outside of the forum’s discussions but couldn’t really find answers for my questions. Lastly, if you could please point to a replacement battery for the aux, that would be much appreciated! Thanks in advance!

[TOPEC]

I believe AC DELCO seems to be the only one that makes a battery with similar physical dimensions n battery specs.

[Qsilver7]

Originally Posted by bavautosport

... Lastly, if you could please point to a replacement battery for the aux, that would be much appreciated! Thanks in advance!

AGM LN1 which is a 140R/H4 battery class size for the auxiliary battery. Rock Auto sells it and I believe (from the past aux battery threads)...the AC Delco brand can be purchased from a GM dealership. (?)

[stocktree]

It's 8 years old. That's really pushing it. Replace it.

[bavautosport]

Much appreciated for all of your replies. Ordered one from Rock Auto. Can’t wait to install

[Dking078]

Typically not too many warning signs.
Atleast with my F10 which had intergral active rear steering, the low aux made the system go on the frits.

The batteries were a bit uncommon years ago and the dealer got my wallet on that one

[Qsilver7]

Originally Posted by bavautosport

Much appreciated for all of your replies. Ordered one from Rock Auto. Can’t wait to install

Thanks for the update.

Just some reminders…don’t forget to vent the aux battery (since it is enclosed)…there should be a little black elbow that connects the vehicles vent tube to the vent hole in the side of the battery. Don’t throw that little black elbow away when you remove the old aux battery. Also, don’t throw away the little red protective cap over the positive battery terminal on the new battery BEFORE removing the knock-out plug that is designed into the cap. You’ll need that little plug to close off the other side of the aux battery so that the gases vented by the battery don’t release inside the vehicle…but will go out the vent tube to the exterior.

You can see the knock-out plug circled in green in the pic below…again, you’ll need it to plug up the hole on the opposite side of the battery you connected the vent tube to (see 2nd pic below for little black elbow that connects the gray vent tube to the battery):

[50iXman]

We have 2 batteries?

[bavautosport]

Originally Posted by Qsilver7

Thanks for the update.

Just some reminders…don’t forget to vent the aux battery (since it is enclosed)…there should be a little black elbow that connects the vehicles vent tube to the vent hole in the side of the battery. Don’t throw that little black elbow away when you remove the old aux battery. Also, don’t throw away the little red protective cap over the positive battery terminal on the new battery BEFORE removing the knock-out plug that is designed into the cap. You’ll need that little plug to close off the other side of the aux battery so that the gases vented by the battery don’t release inside the vehicle…but will go out the vent tube to the exterior.

You can see the knock-out plug circled in green in the pic below…again, you’ll need it to plug up the hole on the opposite side of the battery you connected the vent tube to (see 2nd pic below for little black elbow that connects the gray vent tube to the battery):

THANK YOU! Truth be told, I did forget about them! Much appreciated!

[Qsilver7]

Originally Posted by bavautosport

THANK YOU! Truth be told, I did forget about them! Much appreciated!

Originally Posted by 50iXman

We have 2 batteries?

Yes...but it can also depend on your options...but most f15 X5s have a dual battery setup...with the PCU (power control unit) sitting between them. The PCU monitors/assists the aux battery which is why it may last a bit longer than the main battery.

If you remove the plastic cover below the rear of the cargo floor...you can verify if you do or don't. The smaller aux battery will be to the right of your main battery.