#automobiles + #bmw-i3

AUX18L Auxiliary and Start/Stop Battery, by East Penn

good 12v battery replacement vid

We used the Remy 12V Battery AUX18L

In the US it's important to know that you can use the: Energizer TX24HL AGM Motorcycle and ATV 12V Battery​ as a replacement for the 12 volt. It costs $105 at Amazon. Its been working flawlessly since November of 2023. It may be important to note that in my 2014 the entire car went dead and I had to watch a YouTube to find the emergency hood pull. I had bought the car from a dealer in 2017 so my original 12 volt was between 7 and 9 years old. Absolutely amazing.

I’d caution slightly. This battery seems to be a different physical size than the OEM, and the terminals look different as well. I like this one, because it is a one for one replacement: https://remybattery.com/start-stop-aux18l-auxiliary-battery.html

I worked with Ohmmu to ensure that its LFP battery would work well with an i3. The i3 DC-DC converter's output voltage is ideal for an LFP battery. The 0.5V higher resting voltage of Ohmmu's LFP isn't a problem with an i3's 12V electronics because 12V components are designed work well with the 14.0+ output voltage of the DC-DC converter. The higher resting voltage and the much more flat voltage vs. charge level curve of a LFP battery means that the risk of all of the spurious DTC's being stored when the OEM battery's voltage drops too low when it fails isn't as great with a LFP battery. My Ohmmu LFP battery has been in our former 2019 and current 2021 i3's for about a year without any problems.

If your car still has its original 12 volt battery, your problems may be caused by a 12 volt battery failure. They tend to fail within 4 or 5 years, and, when they do, the car becomes completely inoperable.