[MrNurse]

I tried to start my car and it wouldn’t start. It would try to crank and then wouldn’t anymore when I tried the next day.
I have attached pics of warnings the morning it would start.

1. Is it the battery?

2. What type of battery? It’s impossible finding any info on the M850i, especially something as simple as the battery. Advanced Auto Parts says that the H5, H8, H9 battery groups all work for the M850i but the H9 is much larger than the H5. My stock battery looks more like the H5 size. I tried to google the battery group but no info as well.
Im trying to find the exact battery I need (seems to be $280) that ships to me asap/pick up bc I use that car for work.

I’m thinking to pick up this H5 battery as it seems to be somewhat local to me.
https://shop.advanceautoparts.com/p/...agm/10700670-P


Any info would be appreciated! Thanks!

[claykin]

Probably not the battery. You'd receive a battery related message in iDrive if voltage is low.

Do you have bimmerlink and a supported odb2 reader? If so you can read the fault codes and proceed from there.

Typically Drivetrain Malfunction messages where it says continued driving not possible means the ECU has disabled starting/driving.

Time for a tow to the dealer.

[Tenac]

Just FYI the battery itself in the car has all the details needed to match to another battery... Amps, type etc... Also most BMW's have a 2D barcode on the battery you can take image of that and it will point you to the webpage link.

Curious, because I think I agree with claykin seem like the battery is fine, specially if it tries to crank and you do not get a message of voltage low. I'd get it towed in.

[JCtx]

Even our lowly Porsche Macan sport edition (company car) with a 2.0T 4-banger has an H8 battery at the back too (just replaced it), so I really doubt a large V8 would have anything smaller, but guess it's always possible. I'd definitely get what you have, so just check the specs on the battery (Ah rating, and CCA), and you'd know which one to buy. If you get anything different (especially the Ah rating), you'd have to re-code it (or most likely, a dealer), so better to stick to the original Ah spec.
But yes, seems like you have something more serious that the battery, even if the battery also needs replacing. Good luck.

[bmwfire]

Originally Posted by MrNurse

I tried to start my car and it wouldn’t start. It would try to crank and then wouldn’t anymore when I tried the next day.
I have attached pics of warnings the morning it would start.

1. Is it the battery?

2. What type of battery? It’s impossible finding any info on the M850i, especially something as simple as the battery. Advanced Auto Parts says that the H5, H8, H9 battery groups all work for the M850i but the H9 is much larger than the H5. My stock battery looks more like the H5 size. I tried to google the battery group but no info as well.
Im trying to find the exact battery I need (seems to be $280) that ships to me asap/pick up bc I use that car for work.

I’m thinking to pick up this H5 battery as it seems to be somewhat local to me.
https://shop.advanceautoparts.com/p/...agm/10700670-P


Any info would be appreciated! Thanks!

Curious to see what it ended up being? I hope you figured it out

[bloozemanAZ]

Welcome to the world of the oddity of the M850i. I say that as not sure if the 840i have the same configuration but at least through 2022 all M850is have two batteries. AGM under the hood near the right passenger windshield compartment and a Lithium in the trunk. The M8 (all variants) only have the Lithium in the trunk.

I'm fighting an OTA update and bought a NOCO Genius 10 which handles both AGM and Lithium. Took about a hour for it to get the AGM into "green". Flipped to Lithium and although it tried to do it I'm pretty sure it didn't do anything. The key being is for the Lithium battery the cars BSM cuts if anything over 14 volts to the Lithium battery. The NICO drives 14.8 so guessing I'll need to pick up the CTEK version for Lithium that drives 14V. There is the irony, i.e., the BMW version rebranded and sold is Lithium only regardless that it states it's not truly compatible with my 2020 M850i given the AGM onboard as well.