Friday, April 1, 2011

MINI-E Dismantle, Battery Pack Replacement

It all started about a two months ago when I sent an email to Richard Steinberg, manager of electric vehicle operations and strategy for BMW North America. I asked him if BMW would replace the battery pack in MINI-E #250 because the original pack now has 53,000 miles and is beginning to degrade so my range is suffering. Richard gave me the usual company line about how the lithium ion batteries are expensive and if they did it for me then they'll have to do it for everybody and it will blow their whole bloody budget out the window.

First we disconnected the high voltage battery
Nonetheless, he said he would call Munich and see if it could be arraigned. A few weeks later Richard sent me an email and directed me to give him a call. I did just that and he prefaced the call by saying he wanted me to know he did all he could, but the BMW top brass wouldn't authorize it. He then told me all about a conference call he had with none other than BMW CEO Dr. Norbert Reithofer, Project i boss, Dr Ulrich Kranz as well as Hugo Vangeem and Marian Hawryluk who are electric vehicle project managers for BMW. Noticeably absent from the discussion was BMW North American president, Jim O'Donnell, but from what I'm told, they don't really let him make any decisions around there anymore anyway.  In any event after some discussion, the answer was "No new batteries for Tom".

I ordered 7 boxes, each with 5kWh
Those of you that know me, know that I don't particularly like being told no. In fact, I've been known to go to great lengths and at great expense to turn no's into yes. This wouldn't be any different. If BMW wouldn't give me a new pack, I'll just install one myself! So the quest began. 

We begin to take out the PEU

I quickly realized that it's not difficult to procure batteries for an EV as there are lot's of home conversion websites you can order anything you need from. It was a cinch to get the same exact cells used by BMW in the MINI-E. So last Saturday it was time to do the dirty work. Luckily, I have become friends with one of the area's leading EV mechanics and he offered his shop and services to do the swap. He really likes the MINI-E, so he looked forward to the opportunity to take one apart.  It didn't take us long to realize that much of the cars electronics had to be removed to replace the battery pack so we figured it would be better if we just did a complete dismantle. EV's are really simple and taking one apart and putting it back together is much easier than an internal combustion engine car, where only a experienced mechanic should even think about doing so.

Opening the PEU isn't allowed: oops!
Lot's of wires to reconnect!


EVERYTHING was removed!
Mind you, this isn't exactly allowed by BMW so there might be some splainin' to do once they realize I took part one of their precious prototypes. In the end, we did the swap, put everything back together and MINI-E #250 is running like new. If anyone want's some more photo's of the car when it was all taken apart, just ask!
PEU & motor assembly is all one piece

The suspension was in great shape
UPDATE: After a week of driving #250 with the new batteries, I can report the range is back to like it was when the car was brand new!
Mission accomplished!

UPDATE #2:  4/2/11: Just in case you didn't figure this out yet, it was an April Fools post and never actually happened. The car still has great range, although it may be starting to have slightly less now that it has been charged over 1,000 times and driven 53,000 miles. I plan on doing a range comparison post soon that will compare the cars range in different temperatures in the first year and second year I've had it.

If I had done what I said I did, BMW would probably be at my door today with a bus load of lawyers and repossess the car from me. Before getting the car, the trial lease participants all had to sign documents that we wouldn't alter the car in any way, we aren't even allowed to change a tire or put on window tint. Besides that, the battery pack is located behind the seats in the car so if we did change the pack, we wouldn't even have to open the hood, let alone dismantle the entire car!  I did take a photo of us removing a muffler, but figured if I posted that one, nobody would have been tricked! I hope you had fun with this!


  1. Tom,
    I'm assuming you got a real deal on the swap out, but how much would it cost for the average person?

    Also, how much further do you think you could have gone on the first battery pack before you absolutely had to replace it?

    53,000 miles doesn't seem like that much to me, and the thought of having to replace an EV's battery pack every two to five years, depending on the annual miles one drives, isn't very enticing.

    In fact, it would potentially to kill the whole argument that EVs are cheaper in terms of their long-term total cost of ownership.

  2. Is this an april fool or not?

  3. If you really didn't have permission for this then I would expect you will have some explaining to do. What do you plan to do with the old batterie. I would expect you to take them to recycle, right?

  4. Tom,
    Thank you for the excellent post.

    I'm glad you took matters into your own hands. I'm thinking a fire might have happened if you allowed the original cells to degrade to the point they became unstable with to much internal resistance thus ignition.

    I don't know why BMW would refuse a battery changeout, after all, think of the bad press they would get if one of their cars ever caught fire.


    Mini-E #183

  5. Degrading at 53,000 miles already to the point it needs a swap out? I'm starting to regret my LEAF order since the battery warranty doesn't cover degradation.

  6. Good one Tom ;-)

  7. Please tell us this is an April Fools joke.

  8. Last April Fools 250 caught fire and was destroyed but if this isn't a joke its a lot more scary than a burned up car.

  9. Would BMW really allow this? You might lose your privileges over this

  10. This can't be real. BMW would be at your home this morning with a tow truck and a subpoena if it were. Good crack though

  11. Tom, your report was breathtaking;)
    I guess, you found a way to install an additional liquid cooling/heating system for the battery pack to make it more reliable. If you did so, some pictures would be great so i can make a similar modification to my MINI E!

  12. Hi Stefan!

    Yes, as a matter of fact I did add active thermal management. I was able to take the system from a recently crashed Tesla Roadster and retrofit it. You know, the MINI-E and the roadster use very similar battery modules, as both are basically from AC Propulsion. I did consult Rob Healy, technical coordinator for the MINI-E here in the US for some advice. He was really helpful explaining to me how to tap into the MINI-E electrical system and instrumentation.

    I'll email you the pictures and instructions, but you're on your own getting the system from a Tesla.

  13. Tom, thank you for the information you sent me! That really looks like a retrofit is possible. Fortunately we have a Tesla-dealership in Munich, so I think I'll contact them next week.


  14. Wow and i thought that i was the only one to tamper with and take apart a MINI E. Good joke though.

  15. Originally it said 31. March as the date of this post. It's correct now, so I can sleep quietly, knowing everything is OK :)

    Really good one though, i fully believed it until the last sentence!

  16. OK, I admit you got me when I read this in the morning. Good one.

  17. OK, April Fools -- I get it now. Got me!

    Of course, in my own defense, I read it first on March 31 at about 11:30 p.m. Mountain Time. ;-)

  18. Re: “Lot's of wires to reconnect!” picture. That looks just like the CHAdeMO connector from a LEAF. Tell me you didn’t add a Quick Charge port too!

  19. Exactly! You got it. Now I can charge at level 3! I figured while I was doing everything else, might as well....

  20. I read through some of your posts and found it really interesting. Especially this one on EV batteries. I'm trying to build an electric mini myself. Check out my blog at and feel free to comment or give advise. Keep up the good work.