13 December 2009

I finally caught the culprit

How many Mini E drivers have this problem charging from the 240 volt wall box in the cold?  Mostly in New Jersey?

Here is what I am pretty sure is happening:

The AC Propulsion electronics (the big brass box under the hood) checks the voltage when you plug it in.  If it thinks it is too high, it won't charge to protect itself, or it will start charging and then see the problem and stop.

Something about the colder weather (maybe combined with a low battery charge) is making it judge the AC line voltage (mains voltage) too strictly.  I typically have over 126.5 volts at the regular outlets around the house.  So at the Clipper Creek charging interface (or wall box), it sees twice that, which is over 253 volts.  (Please Please DO NOT try to measure this directly if you are a civilian.  There are safe meters such as the Kill A Watt which will measure a regular outlet and you can multiply that by 2 for an estimate.)

Normally I would guess the AC Propulsion box is happy if the charging voltage is below 260 volts, but in the winter that threshold has slipped down about 3% and it now thinks 253 volts is too high.  Well, our local power company PSE&G does a very good job keeping the voltage up in central New Jersey.  I don't think there really is a problem from the power companies' point of view until the voltage gets to 128 volts, but I am not having any luck finding a specification.  I just remember that from somewhere.

I think I can prove this to Mini, although they can probably verify it themselves.  Too bad, I was looking forward to the promised house call.  But I am super busy at work right now so I probably would not have time to meet them anyway until January.

If you are one of the Mini E drivers with this issue, try turning on everything in the house before you plug in your E.  The extra load should pull the voltage down a bit and might be enough to make the car judge the voltage as safe.  Don't forget to turn things off again as soon as the car has been charging for 15 seconds, especially the stove or the dryer.  I even ran the Microwave but be sure to put at least a cup of water in it, they don't like to run empty.

I switched back and forth several times, and the car would always continue charging when the line voltage was at 240 or slightly below, but back up at 253 volts it would either not start at all or only blink a few times and then stop.

After all the theories that have come and gone, I am going to be really embarrassed if this gets disproved.  But I am pretty confident this time.  The real test will be tomorrow after the long commute to and from work and the low battery charge.


  1. That's some great work Jim! I knew it had to be something related to the supply because people that were having this problem could charge without incident at locations other than their home. What you're saying makes all the sense in the world. I wish you would have checked my voltage when you came to the restaurant. It could have been more data/proof for your findings if my voltage was lower. I did have the voltage checked about 4 years ago and it was low at the time. So much so that my HVAC contractor was concerned that my A/C units might not have the minimum voltage needed to run them. Anyway, great work!

  2. I will be interested to see how they progress this idea. I was told by my service manager that "they would call" to schedule this home visit. but i have heard nothing for over a week. I called the Mini 800 number and got told to call my service manager. I called my service manager and he went to check and I ended up abandoned on hold. Left him a message at the dealer saying he left me on hold and to call back and never heard from him. I am pretty sure at the end of this experiment i will never buy a Mini. An electric vehicle yes, just not from BMW. Sad, but I have low expectations on this getting fixed at all. I have seen no evidence that Mini even acknowledges that there is an issue.

    I like the turn everything on idea, but with 2 sleeping kids at that time of night it just isn't practical for me. Keep up the good work, I hope that they match your enthusiasm.

  3. Mike

    I guess you don't have an electric stove? Even just turning on a toaster might be enough to get your car to start charging. Then the car will load the supply down by several volts and you can turn the toaster off right away and the car will keep charging.

    Our service rep at Princeton Mini is extremely helpful, I intend to write a letter to his boss saying that Jimmy Garito presents the picture of Mini that will bring back customers. (And Jimmy said you should call him, he would not mind trying to help you.) Maybe you should write to your dealer and tell them their service department has convinced you to never buy a Mini.


    I didn't know you were having trouble too? At the restaurant or at home or both? Sounds like all the excuse I need to drive up for a visit and some pasta. I'll bring my instruments. How about next Saturday?

  4. Mike

    A hair dryer on high might do it. Do you have any electric space heaters in the house?

  5. During my home visit, the flying doctor, the field tech rep and one of the engineers assigned from Germany saw the problems and in my opinion are quite committed to getting to the bottom of things. I am still waiting for follow-up from the field rep but expect that to come shortly.

    As for findings, I can also report that the voltage from the wall box was 250v. In my opinion, the problem is being caused by the protection scheme in the software. What's still curious is why charging would work so intermittently, but I don't know much about the load dynamics of the power grid. I'll keep you posted on any progress I hear.

  6. Jim,
    No I'm not having any problems at either of my charging stations. What I meant was, if you checked the voltage at Nauna's and it was 240 or even lower, it would be right in line with what you are saying because nobody that has charged there has had any problems. Now if you get a reading of 253 or higher there then it gets even more interesting. My guess is you are onto the problem. Also, in the winter, there is less of a demand for electric so the available supply increases. This could be the reason why these charging problems did not surface much until September of later, once everyone shut down their power sucking central a/c units. If you want to stop up to Nauna's to check out the voltage that's fine with me, just let me know when you're coming.

  7. Michael

    Thanks for the voltage reading from your house call. That supports my latest theory. Do you remember if it was 250.0 exactly? I had to load my house down to 249.7 tonight to get the car to continue charging. It worked again. But it is not so cold today.


    I see, I should have read more carefully. I just noticed your restaurant is not on the charger sharing site, I'll go get your address from your blog. Yes, I want to get a reading of your voltage, I bet it is below 250.

  8. Europe power is 230V, not 240V ... a simple +/-10% would lead you to 230+23=253V ... I wonder?!

  9. Jim,
    I was thinking about this during the day and I wouldn't have any problems at Nauna's because I have three phase, 208 service there. I remember when I had the HVAC issue the voltege readings were around 200 and 202 which is low but acceptable. At my home though I do not have three phase service (who does) and I don't have any charging problems. A few times in the summer when it was really hot the wall box tripped into protection mode overnight and the car didn't charge but I always suspected that it was because of low voltage due which will happen on hot days when everyone has air conditioning on. Now that electricity demand is low, the available voltage is higher and causing the problems you and the others are seeing. Did you or any of the others have this problem back in the summer? My friend is an electrician. He's going to stop over my house and take a voltage reading. i'll send you the results when I have them.

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