12 Volt Auxiliary Battery East Penn Deka AUX18L

[spartacus68]

So couple questions, what's the 40AH version for, and if you fitted would it last any longer, or do these batteries simply fail with age regardless of AH rating.

The 40 AH battery is a larger size, and requires modification of the battery tray and a different windshield washer bottle installed to make room for the bigger battery. It was used as stop-gap alternative replacement to get a car back on the road during a shortage of the 20 AH battery. Longevity would be the same.

Interesting - thank you. I'm not contemplating adjusting the battery tray or washer-bottle, the 20Ah will do!

 

[jadnashuanh]

Do you happen to know what software version made this change? And how to check which software version you have in your car?

No, I read it somewhere on the forum. You can probably get an answer from the Genius line or from your service manager. Someone may remember, and post it (again).

 

[alohart]

It used to be, if you wanted to trickle charge the battery, you had to pull the HV disconnect first. Supposedly, that changes, depending on what system software is in your vehicle. Because the vehicle disconnects the 12vdc sockets in the vehicle, you can't use them to maintain the battery...you have to go to the battery terminals themselves unless you wire in a path specifically for that that might be more accessible.

Do you happen to know what software version made this change? And how to check which software version you have in your car?

According to BMW's TIS:

"If the integration level in the vehicle is up to and including 14-03-504, then the high-voltage system must be deactivated.
If the integration level in the vehicle is 14-03-505 or more recent, then it is not necessary to deactivate the high-voltage system."

This is the system software released in March, 2014, so very few i3's ever ran this version and fewer yet still do.

Even though our 2014 BEV was delivered with July, 2014, system software that has been updated to later versions several times, I still disconnect the high-voltage disconnect prior to disconnecting or charging our 12 V battery. It's easy to do and isolates the high-voltage system from the 12 V system, so I do it to be extra cautious with expensive components.

The Integration level is the value of the <i-step> tag in the driver profile backup. Just open this backup in a text editor to find the integration level.

 

[Fisher99]

Thanks Art. Good info.

 

[Bimmer333]

Unfortunately, Honolulu isn't one of the cities with a warehouse outlet store, so I had to order the Deka AUX18L from a local Deka retail partner. The best price I was able to get was $150 including shipping to Honolulu. Remy Battery wanted to charge ~$80 for shipping increasing the total cost to over $200. The price at BMW of Honolulu is ~$210. I wish I had been able to buy one for mtkkk45's $98 price, but Honolulu is an expensive place to live, so I paid the "paradise tax".

Could you let me know who is the local Deka retail dealer here in Honolulu, please? I need a Aux battery replacement asap!
Thank you!

 

[alohart]

Could you let me know who is the local Deka retail dealer here in Honolulu, please? I need a Aux battery replacement asap!

The last time I bought a Deka AUX18L in Honolulu was in 2017 from an auto parts and repair shop somewhere on N. King St. When I tried to buy one in 2023, Deka told me that BMW of Honolulu is now the only local dealer for the AUX18L and that Carquest is a local dealer for the ETX18L, a 20 Ah power sports battery the same physical size as an AUX18L but without a common cell vent line or terminals that would accept the screw-on SAE posts from the OEM battery without modification. Some i3 owners have installed a less expensive power sports battery instead of the AUX18L. Apparently, the OEM SAE posts can be installed on some ETX18L's while others require some grinding of the posts to make them fit.

I didn't want to install an ETX18L and didn't want to pay the BMW tax at BMW of Honolulu, so I installed a lithium iron phosphate (LFP) 12V battery which seems to be working well after 10 months. I had to order it, so if you need a battery ASAP, this wouldn't be a solution. BMW of Honolulu might be the source of your only plug-and-play solution. If you have the ability to modify the OEM SAE posts, you could install an ETX18L instead.