Battery capacity depletion?

I've had my Miev for about three years now. Excellent service so far. But I've been noticing that the capacity of the main battery is lowered from a start of 64 miles to 51 miles. Anyone had this problem? And at what point does the dealer replace the battery under warranty? Thanks...

Is this your range remaining after doing a calibration procedure charge, i.e. drain it down to 2 bars and then recharge letting it go until it stops.

psyflyjohn, as you well know by now, that fully-charged RR number can be anything you want it to be, and I defy anyone to tell me what that number will be when they start charging the car. In our case, both my wife and I started off driving the i-MiEV very conservatively and our RR numbers were very high. Our driving habits have now diverged and the car has around 38K miles: my wife continues to drive conservatively and easily shows an RR in the mid-70's (with Yokohama tires); conversely, I'm a leadfoot and screw up the car's RR whenever I drive it (much to my wife's dismay - and she's reluctant to now let me drive 'her' car). With my second used i-MiEV and its brand-new battery pack I've seen fully-charged RR range from 50 miles to 88 miles (Dunlop EnaSave front and Yokohama rears) - it's all about how we drive the darn thing! I can still do a 70-odd mile round trip to SFO in it.

I wouldn't worry about it. So far, Mitsubishi has been very good about replacing a defective battery; I don't recall there being a specific capacity loss number in the original warranty - as you recall from the many other battery threads, there's a lot of discussion about how to exactly ascertain what the number really is.

BTW, you had posted this new topic in "iMiev News", so I'm moving this topic over to the battery subforum

Do you have CaniOn or OVMS? I'd check to make sure it is charging to 99-100%. The first thing I noticed when my pack went was the night before when plugging it in the RR drifted a few miles from where I left it. That morning, it stopped at 96%, then with each activation of the remote, dropped to 92%, 86%, 76%, and continued to fall each day.

There is also the possibility that, like Malm's car, after 3 years the i-MiEV recalibrates the SoC calculation to account for capacity loss.

The problem, like Joe said, is that RR numbers can be skewed so easily. I can drive very efficiently but with the AC on and see a lower RR after a recharge than if I ran 65-70 mph on the highway without AC. The AC would be off in both instances after fully charging.

The dealers will replace the battery if it fails to charge to 16 bars (known to many of us that one cell isn't in the same voltage range as the rest). Even with capacity recalibrations, you may see fewer available miles, but the car will still charge to 16 bars as long as all cells are reaching 4.1 volts, no matter the gradual capacity loss.

PV1 said:

The dealers will replace the battery if it fails to charge to 16 bars (known to many of us that one cell isn't in the same voltage range as the rest). Even with capacity recalibrations, you may see fewer available miles, but the car will still charge to 16 bars as long as all cells are reaching 4.1 volts, no matter the gradual capacity loss.

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That's my understanding as well - Mitsu will replace a defective battery, but not one which still functions properly despite a reduced range. IIRC we all signed a certificate when we bought the car that explained as the car and battery aged, it would go fewer and fewer miles and this was not a warranty issue. I think I've seen 80% range at 50,000 miles mentioned somewhere and this is what we should expect - A still normally functioning car which only goes 4/5ths as far as it did when it was new

Don

"There is also the possibility that, like Malm's car, after 3 years the i-MiEV recalibrates the SoC calculation to account for capacity loss."

Yes, for me that's it. Recalibration of capacity after 3 years and now giving RR in line with the new calibration.

I think if we notice a loss of more then 30% in range (not in capacity) after five years or 100.000 km, that´s to much for normal degradation, so we should have our battery replaced. At least, it is what Mitsubishi Portugal said to me. 30% degradation can be only 20% of loss in range, because of the extra capacity that the car don't uses when it is new. I believe i'm not to far off a loss of 30% in capacity, but I think only lost something like 20% of original range. But remember, this high loss of autonomy in my car is due, in a big part, to the heat of driving it in long trips in the hot summers of Portugal. With the battery at 40 to 50º C several days, I think it's normal to lost more then 8% of capacity in one year.

Now I'm taking care and avoiding temperatures over 30º C in the battery most of the time and I believe the degradation rate was now reduced a lot. Yes, I drive the car with the air conditioner giving cold air to the battery in this hot summer days, I have a 10% reducing in autonomy with this procedure, but temperatures in the battery are no more riching 40º C.

I'll drive it down to one or two bars to force a recalibration and see what happens. I am very much a creature of habit, and have an expectation of at least 45 miles driving capacity for this car through the warranty period. If it drops to below that, I will have to get rid of it. I'm not replacing a battery in it - as that seems to be the equivalent of replacing a motor. I'm beginning to think that buying the Miev, with it's paltry battery capacity may have been a mistake. We'll see....

psyflyjohn said:

I'll drive it down to one or two bars to force a recalibration and see what happens.

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I think the car will not recalibrate its capacity simply doing that. So, your RR will not change with that. I had gone many times to 0,0% SoC and never saw it recalibrate after a charge to 100%.

The car evaluates its capacity every moment, like the Nissan Leaf does. Its hidden somewhere in it (unfortunately, Canion can't show us the value, yet). But I think in first three years it doesn't take notice to the value. But at the end of that 3 years the car looks finally to it (a mean of the value of a time interval) and recalculates.

Its possible that after some time the car uses the value much more often to recalculate the capacity. Mine seems to be doing it now at least every week, because it charging now a little less every week (maybe 0,5 wh less every week) in each bar of 5%. But that may be do to other things, like temperatures increasing in this time of the year.