Charge time at 240 volts 12 amps

A few days ago I posted results from running the battery way down past zero.  And then I charged it over night at 12 amps with the big 240 volt charger.

It took about 12 hours to go from zero to 100%.  This is much less than half of the  charge time at 120 volt 12 amps, which I measured at well over 30 hours back in the heat of summer.  See an older post.

But it is cooler now, and the battery fan runs much slower.  I suspect that is the major difference.

One of these days I will analyze my log file (now posted in with the blog links on the right) and see if I am getting noticeably more juice into the battery at work in this cooler weather.  But I can't do it right now, I am spending too much time driving my Mini E.

By the way, I am noticing some trouble getting the Mini E to start charging from the 240 volt big box when the car is set for 12 amps.  Sometimes it starts and stops, and I have to pull out the plug and put it back in, sometimes twice.  At first I thought that was because I had run the battery down so far in the experiment a few posts back.  But now I notice it even when the battery is above 25%.  Maybe it has always been like this, and I only noticed it with the small 120 volt charger that can only be used at 12 amps.  It is only recently that I have started just leaving the car set for 12 amps almost all the time because it usually charges fast enough overnight to reach 100% by morning.  The idea is to draw most of the power late at night when the grid load is low.

Staying warm

Mini wants the air recirculation control off most of the time.  I agree generally, especially in combustion powered cars where carbon monoxide poisoning is always a danger.

But in the Mini E the story is a little different.  First, the colder September weather now  in the North East US means using the cabin heater.  And I can stay warmer while using less power when the air is recirculating.  Besides, the battery ventilation is always pulling air out of the cabin, even if only through air leaks when the air is set to recirculate.

Now I would like to use heat with the cabin air fan off, since the lowest setting is still too high for these 40 degree mornings.  The battery fan draws enough air though the cabin ventilation vents. But the heater won't come on without the cabin air fan being on.  So the next best way to reduce cold air ingress is to use the recirculation button.

Of course, Mini set it on a timer to turn off after 5 minutes or so. When I notice it getting cold again, I push it again.

There are conventional Minis where I work, so I'll have to ask if this functions the same way on the gasoline powered models which have waste heat to spare.

I would like to see a reversible air flow where battery heat could go into the cabin, but maybe that would not work.  Maybe that was too much to get into a prototype.  In any case, the heater load appears to be much smaller than I expected.  I always assumed the heater in winter would be the Achilles' heel of electric cars.  So far from my measurements (see earlier posting) the heater load looks small. 

Running on empty

Today I heard that I will not get one of the left over charging stations to install at work since I work in Pennsylvania, and the Mini E program is only setup to supervise charge station installations in NJ, NY, and CA. Fine, I understand.

So it is time to see what happens when you drive a Mini E well past zero.

In a previous post I noted that it can take awhile to actually get the gauge to stay at zero. When it first reaches zero, it tends to bounce back up as high as +3% when regenerative braking is used or just when standing at a stop light.

Tonight I purposely kept driving past the point at which the gauge stays at zero. With the heater running. Just driving around the block by my house.

I got almost another ten miles as the maximum power slowly declined. There is not a road speed limit per se as the charge drops below zero, but a torque limit that gets greater. So you can still go fairly fast on level road or downhill, but I got to the point where a moderate hill limited me to 15 mph.

The real issue is that it doesn't want to start charging when it has been driven well below zero. I finally pulled out the 120 volt portable charger, and it would accept charge from that. After a few minutes charging at 120 volts, the car would accept 240 volts at 12 amps. Then I bumped it up to 32 amps. No problem. A few minutes more and I bumped up to 50 amps. OK. But it was almost ten minutes before the gauge went above 0%.

Also, the charge gauge needle never drops below zero while driving. That range between Zero and Off is not a "negative zone". It just makes it clear when the car is on or off. The digital gauge never shows negative either.

So I am not worried about shorter range in the approaching winter. I can make do with the 120 volt charger at work. My 120 mile commute has usually left me with 20 miles of range when I get home after also charging at work with the little box. And I can get over 30 miles left when I arrive home if I am careful. So as the heater gets used and colder weather reduces the range a bit, I'll be fine. Now I know there is another ten miles in there if something goes wrong. I hope I never have to use it again though.

Heater power consumption at lowest setting

One hour twenty five minutes of only heater use with lowest fan and lowest heat setting consumed 4% of charge. The cabin temperature went from 47 degrees F to 64.

Headlight power consumption

Four hours of only headlights on consumed 3% of charge.

I don't think we need to worry about headlights reducing the range noticeably.

Heater power consumption

Running the fan at its lowest speed with the heater at maximum for 1:55 drew the charge meter down 9%.  I don't expect to need max heat often, so I suspect I'll have enough range this winter.  My drive is typically around 1:35, and I have often preheated my cars in the morning during winter with a 900 watt automotive electric heater.  So I probably won't need heat the whole drive.

I took the measurements this morning with the car fully charged, windows open and in the garage.  Ambient temperature in the garage started at 62 degrees F, same as cabin temperature.  After the one hour and 55 minute test, the ambient temperature read 65 and the cabin was 79.

Mini announced a while back that there are some extra high power chargers available for lessees to install at work, now that all the high power chargers have been installed at the homes of  lessees.  I use the low power portable charger at work and have always had a comfortable margin of range for my 3+ hour commute, even in the hot weather where I was running the AC a lot.  But I don't know about the winter when aerodynamic resistance increases, rolling resistance increases, batteries get "stiff" and the heater is on.

At this rate of heater power consumption, I'm not worried.  But it will be nice if they grant me a second charger.  But if they don't, I will deal with it.  I am driving the Mini E this winter, whatever it takes.  I expect it will not be a problem, since everything else has performed as expected or better.

I tried making measurements a couple weeks back using the "Amp Hours per 100 miles" reading on the dash board.  There is too much filtering however, so I could not get numbers that looked trustworthy.  My method was to zero all the gauges, coast in neutral down a small hill for 0.1 miles and then run the heater or AC for ten minutes.  If it worked, it would have given a result in less time.  I'll make some more readings with the longer method described at the beginning, but at different heater settings and post them later.

The monsoon is over

A couple weeks back we had some very wet weather again in New Jersey.  I recall reports of seven inches in one day in my county.  I was out driving #458 in some of the heaviest rain on the weekend without any problems.  I admit it is a curious feeling to pull in the garage out of rain so hard that visibility is down to a few car lengths, and then plug into a charging box that puts out 16 horsepower at 240 volts.  Again, no problem.  Big grin on my face.

(You know, it takes about as much time to plug in this car at home as it does to plug in my mobile phone, which I also do when I get home.  But I never spend any time at the gas station.  Another big grin.)

Then on the following Monday it was still raining and I went to work on the low roads along the Delaware river again.  Lots of big puddles.  Not a single problem.  Even when I hit puddles too fast that were bigger than I thought.

I know I sound like a stuck record but we really like this car.  I hope they hurry up and put something like it up for sale.  I cannot imagine a Nissan being this  nice.  But we won't ever buy a piston car again if there is anything close to this available.

109.4 mile average range

I now have data on thirty trips to work where I started at 100% charge. (Click on the title of this posting to see the spreadsheet if you want the details.) Most of these trips were about 60 miles, mostly not on the freeway and averaging just below 40 mph with the stop signs and lights. A few included some freeway travel, but the best I can do with out going well out of my way is about half on the freeway.

The average of trip distance plus estimated remaining miles upon arriving at work is 109.4 miles. This is for mid June through August traveling in New Jersey and Pennsylvania. Some use of AC, some not, for that level of detail see the log spreadsheet.

For those who have not seen the display in the Mini E dash board, the photo at the top of my blog's main page shows the best estimated range I have achieved. It takes a couple cycles of driving at average speeds in the low 30 mph region for the estimate to creep up to that 140+ mile level. But I can reliably exceed 120 miles on one charge just by driving gently. I usually don't, but I can at any time.

Other bloggers have said they checked range when using "hyper-mile" techniques but only for 10 miles or so. The only accurate way is to start at 100% charge and hyper-mile until you reach zero. Or hyper-mile for well over a hundred miles on several charge cycles and then the estimated range reflects how you have been driving. You can't spend most of your time as a "lead foot" and then hyper-mile for a short distance and expect the averaging algorithms to catch up that quickly. The estimates would bounce all over the place if the filtering time constant were that short.