Monday, May 2, 2011

Infrastructure Issues? Did MINI-E #250 cause a Transformer Meltdown?

When I arrived at work a few days ago, I plugged in as usual, just to top off my charge and be ready for the next 100 miles or so. However after about a half hour, I noticed some of the power in the restaurant went out. Not all of the power, just about a third of it. I have seen this before, so I knew exactly what happened. I had lost one leg of the buildings three phase electric supply. I quickly walked outside to the utility pole to take a look and just as I imagined, one of the transformers had a wire that was disconnected and was arcing with sparks falling from it.

I quickly called PSE&G, and they arrived about a half hour later and quickly repaired the wire and the restaurant was back to normal and my car resumed charging. Since the wire was arcing and sparks were falling, the Montclair fire department was on scene and made sure nobody walked under the area. 

Now here's the problem: This happened about six months ago and at that time my car was also charging when the problem occurred. The PSE&G technician that repaired the line asked me "What do you guys have in the restaurant, I've never seen a the same transformer wire meltdown like this twice in six months" He than said the wire was all charred and looked like it had been in a fire. He suggested I call my electrician to better "balance the load" at the restaurant or this problem will continue to happen. I get what he's saying, perhaps the load isn't balanced well and I should analyze it and properly spread the load evenly among the three phases. However, I built the building eleven years ago and never had a problem, now this has happened twice in the past year that I have been charging #250 there, so I am inclined to think while there was an existing balance issue, charging the car at 12 kWh is definitely the draw that pushed it over the limit.

One of the things I have said I love about the MINI-E is it's ability to charge so quickly. It can charge up to 50amps at 12kWh and completely charge the 35kWh pack in about three hours. Compare that to the Nissan LEAF which only has a 24 kWh pack, and still takes eight hours to charge because it can only charge at 3.3kWh. This means it can only accept about 1/3 of the electricity that my MINI-E which isn't great when you want to charge up quickly, but definitely easier on your utility company. I definitely think this reason is why most of the major auto manufacturers are setting the charge rate of their EV's at 3.3kWh (LEAF & Volt) or 6.6kWh (Focus, Coda) instead of higher. Future BMW EV's (ActiveE & i3) will be limited to 7.7kWh which is probably a good decision, as balancing fast charging against not wanting their customers to blow up their transformers needs to be considered. Tesla on the other hand is going to continue to allow charging up to 16.8 kWh and uses the same AC Propulsion technology that allows the MINI-E to charge at such a high rate. They don't seem to be concerned about supply issues, only time will tell if they are correct. I know this, if after plucking down $60,000 or so to buy a new Model S, you find out that you keep overwhelming your utility supply and cannot charge your car, you aren't going to be very happy.

There will be growing pains. As electric cars become more and more prevalent, expect to hear about electricity supply problems from time to time. The one good thing about relatively slow adoption of electric cars is that it will allow the utilities to identify weaknesses and problem areas, and upgrade what need to be upgraded before there are millions of EV's driving around everywhere and not enough supply to charge them.


  1. A colleague is building a new home and just now having electric connected. They ask the size of the home - presumably to appropriately specify power sizing, etc.
    So if your property similarly was specified based on it's needs years ago, then you add the huge draw of car charging, isn't it likely that something previously ok is now stressed?

  2. Ian: Yes and No. My commercial building uses a lot of power so the car really is just a drop in the bucket. However, as I said I have three-phase power supply, different than what you would have in a home. So while I have plenty of power available, I need to balance the usage so that any one leg of the power doesn't have a much bigger draw than the other two legs which is evidently happening. The car was just "the final straw" that pushed the one leg over it's maximum power supply. I'll have my electrician move some of the breakers around, and balance my power a bit better and all should be good.

    Home charging should primarily take place overnight when electricity demand is low and there is plenty of power available. All new EV's allow you to set what time the car will charge so you can set it to begin charging at 1:00am even if you actually plug it in when you get home from work. As long as you give the car enough time to complete charging before yo leave the next day, the later you set it to charge the better.

  3. Ideally an electric car should have enough range to only have to be charged once a day or less not twice as many people with long commutes are having to do. Hopefully as battery costs come down ranges will go up to make this twice a day charging thing unnecessary.

  4. Anonymous: I do agree with that. You shouldn't try to fit a square peg in a round hole.
    Just so you know, I don't "need" to charge at work. My round trip is 63 miles. I do it just because I like to have the car fully charged just in case I suddenly need to drive far (which rarely in necessary).

    I also charge at work because the electricity is much cheaper, .12 compared to .18 per kWh

  5. Tom, can you charge at a lower rate than 50 amps at work? I remember you said you do not always plug in right away. This might be more of an advantage as the weather gets hot and the AC is running more.

    But I bet you have a major balance issue. Since you have three phase, your 208 volt charger is always drawing from two legs of the three. only 120 volt loads draw from a single leg to neutral.