Battery Deka or OEM BMW

You can get an Deka AUX18L from batterymart.com for $159 shipped to your door. Deka is the OE manufacturer of the BMW battery for the i3. My original battery lasted 7 years, it’s a no-brainer.

But during the ownership i found it really reliable, the only things i needed fixing were: battery (it was the original one over 7 years old), tyres and brake discs/pads (consumables on any car) and the regular oil/filter services.

The battery is most likely to outlive the rest of the car. No need to worry. If the car has enough range for your daily need, then keeping it will be the best option.

If you really want to buy this one (I find the price quite high, but I don’t know the specific market in Norway), buy an OBD adapter and EVScanner app on iOS with the BMW module. You can check the SOH of the battery and the general state of it as the replacement could be quite costly (around 1500 per module and you could have to replace up to the six if all fail or the BMS). I’d guess the SOH would be at best around 85%, maybe less. The engine itself is pretty reliable as it’s a detuned B48 from the 330i. Go to the infotainment and check the stats from factory and the percentage of eDrive kilometers (full electric) compared to the total kilometers, it would give you an idea of how the car was used and how much charging it got. This specific model of car is great to drive if you can charge everyday and you drive mainly short distances. I do around 80 km daily, almost all highway and my average consumption on those drives is 3.5 liters and 10 kWh/100, so it’s about 2/3 of the cost of my previous car, while beeing a lot better to drive. I’d still buy a 320 or 330i instead because there will be less things that could fail and I would probably not want to get such a high mileage PHEV without knowing how it’s been previously used. Source: I have a 330e from 2021 with 112k km and the SOH of the battery is 90% with around 1400 cycles. Average consumption since factory is 4.9 l/100 km and about half of the distance have been made fully electric.

I took a drive in my i4 a couple of weeks ago that estimated I'd get home with 4% battery. Guess what I rolled into the garage with..... 4% battery. These modern systems are pretty damn accurate.

I just replaced both batteries in my 2018 740iX. Was original battery (build date was Aug 2017) so actually lasted 8 years which was surprising given other problems I had with the car!

I still have the original BMW battery on my 2005 e46 325i , I used a battery tester on it and still say it’s good

I use Deka sealed batteries so less offgassing messing up terminals.

The only issue we’ve had with it is recently a bunch of warning lights started popping up randomly but all at the same time. I assumed it was a wiring issue or something since none of the systems it said were disabled actually were. Dealership couldnt replicate it so it took a couple weeks of bringing it back and forth every time it happened before they were able to see anything on their end. Replaced the battery and it’s been fine since.

My new BMW X3 was reliable.

It reliably would NOT start whenever the temperature dropped below -20C, even with a battery tender on it. The dealer couldn’t find anything wrong with it.