12 v battery change

[johnjackgallag]

I have 2019 rex s. is it worth just buying a battery replacement and installing even though no signs of needing one? If I buy the replacement to have on hand and periodically trickle charge it just in case?

 

[mojo]

To an extent, it depends where you are in the world. In Europe the batteries are relatively cheap from a BMW dealer, so it probably makes sense to just do this as preventative maintenance at 5 years old. But in North America they are quite a lot more expensive (from a dealer) so the decision may be a bit more difficult.

I personally would not plan to keep a lead/acid battery on trickle charge for any length of time, because it is likely to slowly deteriorate - better to get a fresh one when you need it.

 

[alohart]

is it worth just buying a battery replacement and installing even though no signs of needing one? If I buy the replacement to have on hand and periodically trickle charge it just in case?

That's what I've done twice so that I would have a replacement battery immediately when needing it. In 2018, I bought a battery for our 2014 i3 that we bought new from a local East Penn Manufacturing battery dealer for considerably less than our BMW dealer's price. The original battery didn't begin to fail until 2021, so I stored the replacement for 3 years recharging it ~3 times/year so that it wouldn't self-discharge too much. An AGM battery has a long shelf life when it isn't allowed to self-discharge completely, so I was not worried about my stored battery degrading much. I sold our 2014 i3 within 6 months of replacing its battery and haven't kept in touch with the new owner, so I don't know how long the replacement battery lasted.

Since my 2018 battery purchase, East Penn Manufacturing seems to have limited the sale of its AUX18L to BMW dealers. I could no longer buy one from other local East Penn Manufacturing battery dealers in 2022 when I wanted to store one for eventual installation in the used 2019 i3 that I had purchased. I could have purchased an East Penn Manufacturing ETX18L motor sports battery from local dealers, but that's not an ideal battery for an i3.

Instead, I installed an Ohmmu G1DC22 22 Ah lithium iron phosphate (LFP) battery in our 2019 i3 when its original battery failed after 4 years. When I bought our used 2021 i3, I swapped its original battery with the LFP battery in our 2019 i3. I have a second Ohmmu LFP battery in storage for installation when the Ohmmu battery in our 2021 i3 fails. I'm hoping that a LFP battery will have a much longer life than the OEM battery.

 

[robthebold]

I have 2019 rex s. is it worth just buying a battery replacement and installing even though no signs of needing one? If I buy the replacement to have on hand and periodically trickle charge it just in case?

If your battery died tomorrow, what would you pay to be able to snap your fingers and have a new one installed yesterday? I bet wrong, don't be me.

 

[tob1as]

I’m with @Mondomensch. I replace my 12v every 3 years profilactically (learned about sourcing and how when the original one failed at 3 years - DC charging was starting to glitch/trouble opening charge port in cold weather, weird dash messages …). It’s a low cost simple procedure ($150) to not get stranded in the middle of winter. Certainly have read about people getting a lot longer life out of theirs, but I live in extreme hot/cold climate (and the i3 lives outside), so this is my personal preference. No need to bother having a battery replacement sit on the shelf and needing to nurture that.

 

[mojo]

Probably the worst bit is that sometimes you get very little warning that it's about to die (maybe a cell plate collapse happens quickly - I'm not sure). In the UK there was a tale of someone having theirs fail in an indoor car park, and they had to pay to have a special tracked vehicle extract it because a conventional recovery vehicle would not fit in the building!

(Yes, I know - it would have been far cheaper to call in a mobile specialist to come and change the battery in situ, but they didn't know that).

 

[tob1as]

Probably the worst bit is that sometimes you get very little warning that it's about to die (maybe a cell plate collapse happens quickly - I'm not sure). In the UK there was a tale of someone having theirs fail in an indoor car park, and they had to pay to have a special tracked vehicle extract it because a conventional recovery vehicle would not fit in the building!

(Yes, I know - it would have been far cheaper to call in a mobile specialist to come and change the battery in situ, but they didn't know that).

Yeah, the three design decisions BMW should have altered: non-standard 12V battery, non-standard tires (!!!), leaky frunk. Others?

 

[Mavourneen19]

To an extent, it depends where you are in the world. In Europe the batteries are relatively cheap from a BMW dealer, so it probably makes sense to just do this as preventative maintenance at 5 years old. But in North America they are quite a lot more expensive (from a dealer) so the decision may be a bit more difficult.

I personally would not plan to keep a lead/acid battery on trickle charge for any length of time, because it is likely to slowly deteriorate - better to get a fresh one when you need it.

If your battery died tomorrow, what would you pay to be able to snap your fingers and have a new one installed yesterday? I bet wrong, don't be me.

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.

 

[Edszhi1]

That's what I've done twice so that I would have a replacement battery immediately when needing it. In 2018, I bought a battery for our 2014 i3 that we bought new from a local East Penn Manufacturing battery dealer for considerably less than our BMW dealer's price. The original battery didn't begin to fail until 2021, so I stored the replacement for 3 years recharging it ~3 times/year so that it wouldn't self-discharge too much. An AGM battery has a long shelf life when it isn't allowed to self-discharge completely, so I was not worried about my stored battery degrading much. I sold our 2014 i3 within 6 months of replacing its battery and haven't kept in touch with the new owner, so I don't know how long the replacement battery lasted.

Since my 2018 battery purchase, East Penn Manufacturing seems to have limited the sale of its AUX18L to BMW dealers. I could no longer buy one from other local East Penn Manufacturing battery dealers in 2022 when I wanted to store one for eventual installation in the used 2019 i3 that I had purchased. I could have purchased an East Penn Manufacturing ETX18L motor sports battery from local dealers, but that's not an ideal battery for an i3.

Instead, I installed an Ohmmu G1DC22 22 Ah lithium iron phosphate (LFP) battery in our 2019 i3 when its original battery failed after 4 years. When I bought our used 2021 i3, I swapped its original battery with the LFP battery in our 2019 i3. I have a second Ohmmu LFP battery in storage for installation when the Ohmmu battery in our 2021 i3 fails. I'm hoping that a LFP battery will have a much longer life than the OEM battery.

Note: Based on their web page the shipping is only $19 for anywhere in continental U.S. (from Prescott, AZ). Now then, I fear doing the wrong thing when dealing with modern day electronics. And the Internet doesn't always have the correct information out there for replacing automotive equipment. Which youtube vidoe should I follow when I replace my 4 year old 12 Volt battery? Thanks in advance.

 

[tob1as]

Note: Based on their web page the shipping is only $19 for anywhere in continental U.S. (from Prescott, AZ). Now then, I fear doing the wrong thing when dealing with modern day electronics. And the Internet doesn't always have the correct information out there for replacing automotive equipment. Which youtube vidoe should I follow when I replace my 4 year old 12 Volt battery? Thanks in advance.

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
For instructions this video was what I used:

 

[Mondomensch]

Wow, didn't appreciate quite how tight the clearances are to get at the battery. Appreciate the tiny details in the linked video.

 

[tob1as]

Wow, didn't appreciate quite how tight the clearances are to get at the battery. Appreciate the tiny details in the linked video.

A word of encouragement: I don’t have small appendages, but I was able to do it. That said: Be careful to not damage the windshield wiper reservoir. I may have done that the first time and ended up with a persistent leak (now fixed).

 

[alohart]

I’d caution slightly. This battery seems to be a different physical size than the OEM, and the terminals look different as well.

Yes, any 12V battery that is taller than the OEM battery will make installation more difficult. The Ohmmu G1DC22 LFP battery is ~½" taller which makes attaching the battery's bracket more difficult but doable. Ohmmu's LFP battery for a Rivian truck is slightly shorter so would fit well but is more expensive. Both batteries are thinner, but Ohmmu includes a spacer that makes them fit well. The battery's width isn't so critical as long as it fits in the battery tray.

The OEM screw-on terminals don't fit most non-OEM batteries, so they must either be modified to fit or different screw-on SAE posts must be used. I used SAE posts that Ohmmu designed for its Tesla Model S LFP battery. I still had to grind a small amount of brass off 2 sides of each post so that they would fit snugly.

 

[alohart]

Now then, I fear doing the wrong thing when dealing with modern day electronics. And the Internet doesn't always have the correct information out there for replacing automotive equipment.

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.