Best approach to deal with dead battery

[panzer948]

Today I discovered my 2015 M4 in my garage with the passenger door partially ajar. While closing it I noticed the car was completely dead, no dome lights, nada. I am a bit surprised an ajar door could kill the battery as I thought there was a timer to cut off interior lights, etc., although the car had been sitting 4-5 days. Anyway, maybe it's time since the car is 6 years old with original battery.

So, I have dealt with dead batteries in less complicated cars before by trickle charging them using a fairly mid level automotive battery charger/analyzer (I know mid-level is relative, but if it helps it cost about $80). However, I have heard BMWs are a little finicky with charging and jump starting and know to do this at the posts under the hood. I just want to make sure my regular $80 smart charger/analyzer is ok for the job and not some fancy BMW charger I have seen others talk about. My goal would be to atleast get it down the road to a shop to do diagnostics to see if I need a new battery and hopefully just swap out while there.

Alternatively, should I just take my backup car (very old Jeep) and purchase a new battery (assuming that is really the problem and not some rat that has chewed threw my wires) and install this myself? I assume there is nothing special about doing so in the M4, other going thru the trunk. I have heard of some having error codes from just having the battery out a few minutes. I guess even screwing up the presets is pain enough. Do some shops have methods to avoid that?

[panzer948]

Well, so much for that plan. My charger will not even detect a 12 volt battery system at the posts. When I hooked up a basic multimeter, it is showing like 0.3 volts at various grounded posts! I can't believe it is that low. But the bigger question is how to get to the battery now to check it directly. Maybe there is some corrosion on the battery that needs cleaning.... However, I don't think I can pull the back seats back to access the trunk without the leaver from inside the trunk being pulled to unlock rear seats. There must be a way to get in there.... Manual is no help.

I hate to go buy a new battery on a whim though but it looks like this car isn't moving until I do as I dont think jumping it off is a good idea. Open for suggestions.

[panzer948]

So after finding a few threads on here with same problem it seems getting something thru the back seats to pull on the emergency handle or seat releases is the only way to get to the battery. Why oh why would they leave out a non-powered way to reach the inside of your trunk is beyond me...

https://f80.bimmerpost.com/forums/sh....php?t=1410407

It's getting late so tomorrow I will have to hook up the old tried and true method and connect my Jeep's V8 to the BMW. It's midnight here and I would wake everyone up trying to run that engine now. But my biggest concern is for my multireader to show less than 1 volt there could something more seriously be wrong.

I was serious about rats/mice concerns as I found them actually trying to nest under my hood a couple of months ago. Everything has seemed fine but I now wonder if they could have done some serious damage and its just now catching up with me...

[Bunnny]

It could have been the door left open, but also it can be that your battery might be too old. They usually stop taking charge around 6 - 7 years and need replacement. It also doesn't help that there is still sensors running in the car, so the car should be started every few days for this reason.
If you can get it boosted and going again, drive it immediately for 45 mins to an hour to try to restore the battery.
Otherwise its about $2200 to buy at the dealer, and it must be the same make and model or else it will need to be coded to work with the car also.

I got lucky last spring after winter and saw a low battery message & was able to charge it back up by driving for an hour or two.
Best of luck with this!

[mapster37]

i would be leaning towards some rodent damage since you mentioned that

[behindthen0thing]

Originally Posted by panzer948

Today I discovered my 2015 M4 in my garage with the passenger door partially ajar. While closing it I noticed the car was completely dead, no dome lights, nada. I am a bit surprised an ajar door could kill the battery as I thought there was a timer to cut off interior lights, etc., although the car had been sitting 4-5 days. Anyway, maybe it's time since the car is 6 years old with original battery.

So, I have dealt with dead batteries in less complicated cars before by trickle charging them using a fairly mid level automotive battery charger/analyzer (I know mid-level is relative, but if it helps it cost about $80). However, I have heard BMWs are a little finicky with charging and jump starting and know to do this at the posts under the hood. I just want to make sure my regular $80 smart charger/analyzer is ok for the job and not some fancy BMW charger I have seen others talk about. My goal would be to atleast get it down the road to a shop to do diagnostics to see if I need a new battery and hopefully just swap out while there.

Alternatively, should I just take my backup car (very old Jeep) and purchase a new battery (assuming that is really the problem and not some rat that has chewed threw my wires) and install this myself? I assume there is nothing special about doing so in the M4, other going thru the trunk. I have heard of some having error codes from just having the battery out a few minutes. I guess even screwing up the presets is pain enough. Do some shops have methods to avoid that?

Get the correct charger for one.

The battery has an undervoltage protection that when the voltage drops the battery opens the circuit to prevent further draining and it will read zero.

"BATTERIES WITH "UNDER VOLTAGE PROTECTION"
Some Lithium batteries have an on-board UVP (under voltage protection) that
disconnects the battery to avoid it becoming too deeply discharged. This prohibits the
charger from detecting that there’s a battery connected. To bypass this, the battery
charger needs to open the UVP. There are two options available to “wake up” the
battery - automatic and manual.
During the automatic “wake up” period the LED will flash until the charge program
is started and LED is lit with a steady light. Automatic "wake up" will be active for
maximum 5 minutes.
If the charger is in Standby mode after 10 minutes ( power led is flashing) the
automatic wake up did not succeed. Try the manual wake up.
To use the manual “wake up”, press the Mode button for approximately 10 seconds
to bypass the UVP. During the “wake up” period the LED will flash until the charge
program is started and the LED is lit with a steady light. If the manual wake up is
unsuccessful the power LED will start to flash after latest 10 minutes. Disconnect any
parallel loads from the battery and try again. If the charging does not start after that, the
battery may need to be replaced."

[panzer948]

Thanks for the info. I just picked up the BMW trickle charger from my local dealership (its the only thing in stock around here). But I still need to get a way to bypass the undervoltage protection system. Looking at getting one of those Li battery boosters later today just to jump the car off. One of these. There are some Youtube Vids out there with folks starting F80s with this product. I would rather use this than another car.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[IVM3]

I would try jump starting it with another car first. That worked for me when my battery died overnight. No problems since then.

[SD ///M4]

Originally Posted by panzer948

Thanks for the info. I just picked up the BMW trickle charger from my local dealership (its the only thing in stock around here). But I still need to get a way to bypass the undervoltage protection system. Looking at getting one of those Li battery boosters later today just to jump the car off. One of these. There are some Youtube Vids out there with folks starting F80s with this product. I would rather use this than another car.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

The CTEK Lithium charger is a better charger than the one in your Amazon link for roughly the same money. Make sure you read the instructions and press and hold the button to override the battery protection circuit.

The BMW charger is a re-branded CTEK charger.

[panzer948]

Originally Posted by IVM3

I would try jump starting it with another car first. That worked for me when my battery died overnight. No problems since then.

Ok, may just do that. Will give all this a go tomorrow AM. Believe it or not I spent most of the day tracking down these two devices locally. Then I called it quits for the day.

I did talk to my local SA about battery replacement while picking up the trickle charger. You guys are correct. OEM battery is almost $1900 and the register and recoding would be another $150 ish... I am just hoping the $$ I spent today will keep a new battery at bay. Yes car is nearly 7 years old but it only has 60K miles. If I can save this battery I will be keeping it on a trickle charge.

[panzer948]

Update: Well finally some good news. These two products seem to have been the ticket to saving me a bunch of money. This AM I used the NOCO GB40 Genuis Battery Bost Plus (GB40), just as the following video described:

It didn't do anything at first but on 3rd attempt the car electrics simply came alive. I quickly opened the trunk with the remote and then disconnected the battery boost and happily the car stayed on. I then quickly connected the BMW trickle charger detailed here:

It started off on #2 (soft start mode), then quickly went to #3 (bulk charging cycle). I did a quick check with my multimeter and it was reading in the low 11 volts!

Lesson learned here is that it seems I likely left something on in the car which dropped the voltage low enough for the car to go into the "under voltage protection" (UVP) mode. But without that emergency boots option of the GB40 to overcome the UVP mode, the trickle charger, my multimeter, and the car itself all registers 0 power. I do have a few accessories running in the car, including a dash cam that does have parking mode but also is supposed to cut off once dropping below a certain voltage. TBH, I didn't want to even bring that up as I do not think the dashcam caused the issue. Regardless, I feel I am lucky indeed and will use my new trickle charger on days I don't drive car. I want this battery to last!

Anyway, I wanted to post what I hope is the final outcome and hope that some of my quick digging and questions answered here will help someone else save some time. Thanks again for advice above.

[SD ///M4]

FYI, the BMW charger shown in your last picture is a CTEK charger re-branded by BMW.

[panzer948]

Originally Posted by SD ///M4

FYI, the BMW charger shown in your last picture is a CTEK charger re-branded by BMW.

Oh I realized that right away, even before I called to see if it was in stock Saturday morning. I tried to find the CTEK charger locally by going to a few stores and shopping online but it would take a day or two to get it to me so paid a few extra bucks to pick this BMW version Saturday at my local dealership. I think they had one left and he put it away for me while I drove out to get it. I was willing to pay a few extra bucks more knowing I would get an answer sooner if I was going to pay $2K for a battery!

Luckily this little gem did the trick and by Sunday evening I was on the road. Drove the car for more than 2 hours and its been good ever since. Yes overpriced but hey, it came with a nice bag

All and all I am happy with outcome!

[SD ///M4]

Originally Posted by panzer948

Oh I realized that right away, even before I called to see if it was in stock Saturday morning. I tried to find the CTEK charger locally by going to a few stores and shopping online but it would take a day or two to get it to me so paid a few extra bucks to pick this BMW version Saturday at my local dealership. I think they had one left and he put it away for me while I drove out to get it. I was willing to pay a few extra bucks more knowing I would get an answer sooner if I was going to pay $2K for a battery!

Luckily this little gem did the trick and by Sunday evening I was on the road. Drove the car for more than 2 hours and its been good ever since. Yes overpriced but hey, it came with a nice bag

All and all I am happy with outcome!

Glad that this worked out for you and you didn't need to (unnecessarily) buy a new battery!