Charging Interruption

Has anyone else noticed an interruption in the power drawn by the iMiEV charger? I've seen it occur using either the Mitsubishi 120v EVSE or my SPX, at both 120vac and 240vac. The interrupt lasts anywhere from a couple of minutes to about 20 minutes. At least once it simply stopped charging completely (over two hours) and I had to shut off power to the EVSE and then turn it on again, after which it did just fine. The following image was taken this evening off my TED 5000 display on my Mac. The blue line is the iMiEV Level 2 SPX EVSE power, the red line is voltage, and the green line is a separate power experiment I'm running on a different branch. This particular interruption lasted about ten minutes.

I have a hard time even telling that the car is charging when I'm using the stock 120v EVSE, I rely on the little charging light on the dash being lit and assume that it is. It's so quiet. What do the lights do on the car and the EVSE during this interruption, anything different?

Jenn

Right after I wrote that, I went out to the garage and the charging car was dead quiet, as usual. Suddenly it seemed to "turn on" and I could hear it charging, though still pretty quietly.

Jenn

Sure, I see it about 1:30am when starting to charge at midnight.


i-MiEV Charge Intterupt by JJLINK, on Flickr

Hi Jenn, what you're hearing I think is a pump of some sort running intermittently back there, and I swear I can hear gurgling sounds as well. The actual charging is silent. On my SPX, suspended charging produces a solid green light instead of a blinking green light. On the Mitsubishi charger I forgot to note what it was doing when it suspended charging.

jjlink, thanks for posting your graph, as it confirms that it's the iMiEV's charger which is causing the interrupt. I'll speculate that it could be part of its internal BMS calibration routine. Not a problem, IMO, unless it stops charging completely - especially if one is on the road and needs the charge to get home.

I did notice it, the charging light was still on and the cooling pump also continued to cycle so I put down to the charger having to cool down, but I guess from what you guys have is that it only does it once in a charging session.

Hello.

I recently purchased a electricity consumption monitor and I found this strange behavior. I thought to open a new post, but I thought maybe I had been discussing, and I see that it is.

Three days I've looked, three days I see that interruption in loading, and continues thereafter. I have no idea why.


(the picture is all the electricity usage in 24 hr at home, but the marked zone is almost the car carger)

From what I have learned, guessing what is in the battery is tricky at least.

When voltage suddenly drops and does come up only slowly after removing the load, that is empty but still leaves room for bottom balancing.

When voltage and temperature suddenly rise it must be full. Quick chargers do stop at that point and battery gurus say it might be a good idea for slow chargers to stop as well.

The BMU keeps track of our state of charge by counting ampere hours in and out but it needs the endpoints every now and then to recalibrate.

If you stop somewhere in the middle and watch how fast voltage drops and compare with temperature you get and indication of state of charge and of battery health. That point is chosen randomly to build a more complete picture by adding the results from different charges.

When integrating (time and amps) you see it is not much that gets into the battery after the constant current phase. That is why the gurus say it is not worth to risk battery life for that little and after several charges that final charge might steal more from your battery capacity than you gain from "overcharging" in the first place.

Going long distance with several power sockets visited I try to stay above 3 bars and rarely go above 14. So I can charge the full 16A most of the time saving time.

First, I know absolutely nothing about the BMU in our cars other than what little Mitsu has shared with us . . . . I've read everything I can find, but they're not revealing too much

peterdambier said:

If you stop somewhere in the middle and watch how fast voltage drops and compare with temperature you get and indication of state of charge and of battery health. That point is chosen randomly to build a more complete picture by adding the results from different charges.

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It makes perfect sense to me that this interruption in the charging cycle is evidence of the BMU at work and Peter's answer above seems logical and makes sense to me. I'm guessing he's pretty accurately described what's happeneing

Many here have converted cars to EV's and others have built EV's from scratch. I haven't, but I considered doing so for a long time and read everything I could find on the subject. You can buy pretty state of the art components - Good motors, motor controllers, LiPo batteries, chargers and even BMU's which control the charge process and help equalize the cells as they charge, but . . . . if you buy the best components available and put them in an old ICE with 100K on it, you're going to spend $20K (not counting your labor) and you're still going to have a 100K car (which probably needs a paint job) and you still won't have anything remotely like what you get when you buy an iMiEV. You may not have air conditioning or power steering and you definitely won't have a battery system likely to last you 3,000 charge cycles and 100,000 miles. I'm not aware of any standalone BMU system on the market which cares for a battery pack like the one which came in our car . . . . period

When I test drove the iMiEV, I was DELIGHTED - I told my wife I could easily spend nearly as much money and the better part of a year of my time and still not be able to build an EV half as good as this one. Buying this car seemed like a 'no-brainer' to me . . . . and that was before Mitsu kicked in a $10K rebate

Don

We had discussed the charge interruption on a number of other threads, and I see that I had forgotten to update this one. I had posted these screenshots off my TED5000 display (taken on the evening of 22 March, 2012) elsewhere, but am repeating them here -

The red line represents line voltage and is the nominal 120vac off one of the two power input legs.
The green line (kW) is the day's tail end of my solar generation, showing it decaying to zero as it got dark.
The orange line (kW) represents my other EV charging and is showing zero as nothing was charging.
The blue line (kW) represents my iMiEV, charging at a nominal 240vac.






You can see that about an hour into the charging process the charger paused for a few minutes by itself before starting back up. This is normal, and I surmise that this is part of the BMS testing to see if any cell(s) exhibits an inordinate voltage drop when power is removed. At the end of charge you can see that from the point the power draw starts to decay to the actual cut off by the charger the time is about an hour.

In their cell monitoring unit update reprogramming last year, Mitsubish evidently changed the timeout duration from a nominal ten minutes to six minutes, although I've seen longer durations occasionally, but have never seen TWO timeouts in one charging session.

Don said:

I told my wife I could easily spend nearly as much money and the better part of a year of my time and still not be able to build an EV half as good as this one.

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OT. As the owner of two EV conversions and a couple of spartan high-performance single-seater Sparrows, I completely agree with Don that a DIY conversion of an older vehicle nowadays is definitely not cost-effective (but it's a great father-son/daughter technical project). Don't forget, there were virtually no production EVs available for years, and an EV conversion was the only game in town. We're at the dawn of a new era...

Thought I'd revive this thread as DBMandrake interjected some new thoughts into this old subject in the Topic Is my battery dying?

Specifically, in that thread -

DBMandrake said:

...If the car is at 2 bars or less when you start charging it sometimes after about 10 minutes charging "pauses" for up to 30 minutes where the car and charge point says the car is still charging but the power drawn drops from 3.3kW right down to about 30 watts. I can only assume balancing is occuring, I have not tried putting my diagnostic tool on to confirm this but I think it's a fair bet.

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Over the past six years the charging "Timeout" has been addressed or buried in many other threads as well - here are a few I found -

http://myimiev.com/forum/viewtopic.php?f=23&t=1356&p=7933

http://myimiev.com/forum/viewtopic.php?f=9&t=773&p=5627

http://myimiev.com/forum/viewtopic.php?f=9&t=686&p=4932

http://myimiev.com/forum/viewtopic.php?f=24&t=1894

http://myimiev.com/forum/viewtopic.php?f=23&t=3811

Specifically addressing whether a low SOC (two bars or less) is required for this Timeout to occur, I can confirm that it does not. Over the last couple of days I looked at the power consumption graph for my i-MiEV for two charges: the Timeout occurred both times, and each time I started charging from about seven bars. The Timeouts each lasted about six minutes. The first time the Timeout started about forty minutes after I started charging, and the second time it occurred about 1-1/2 hours after I started charging.

Look a look at the previous post on this page to see a graph of the car's power draw and Timeout while charging.

Now, what we have are two ideas as to what's going on:

JoeS: the Timeout is used to measure voltage sag while charging is temporarily suspended; if it's excessive, the charging would be aborted (I don't know of any instance when that has occurred). I've seen this feature on conventional 12v lead-acid chargers.

DBMandrake: Timeout is used to allow cell balancing at a low SoC (in addition to the usual top-balancing that occurs at the end of a full charging session)

I like DBMandrake's hypothesis as it would explain the variable nature of this Timeout duration, ranging anywhere from 6 minutes to 20 minutes (or even more?).

Just thought I'd reopen this topic, in case anyone is recording CaniOn during this Timeout to confirm DBMandrake's hypothesis that the cells are being balanced during this interval.

JoeS said:

Just thought I'd reopen this topic, in case anyone is recording CaniOn during this Timeout to confirm DBMandrake's hypothesis that the cells are being balanced during this interval.

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As far as I know, Canion can't report the state of the cell balancers ? In which case you could only infer that balancing was occuring by watching for changes in cell voltages.

Diagbox will report the state of each individual cell balancer in real time (active / inactive) and you can see them flicker on and off towards the end of the charge cycle.

I have not had a chance to put Diagbox on the car during a "bottom balance" at 2 bars to see if it is truly balancing that is occuring, as it's difficult to predict when/whether it will do it, and getting the laptop out, connected, booted up and in the right diagnostic screen of Diagbox is a bit of a hassle. But maybe one day I will catch it, especially now I have Canion and a splitter cable so I can run Canion and Diagbox simultaneously.

Display of the status of the cell balancers in Canion would be a great feature if it could be added - the way I would visualise it would be to change the colour of the voltage bar of a cell whose balancer is currently turned on to something other than blue. Then you could see the relative voltages and the action of all the balancers at a glance in a very intuitive fashion...