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So my recently acquired 8-year old 2009 Mitsubishi I-MIEV has a 16kW battery. I believe normally about 14kW would be useable, however I have only ever had approx. 10kW of useable battery.

Last night I deliberately came home in it with very low batter (2 bars). I then left the heating on to try and run the battery down to zero. After about 6 hours of this, the battery was still alive and going. It had spent the last 3 hours in turtle mode with 0 bars displayed. I decided to take the key out, turn the battery off and go to bed.

This morning I turn the car on, to find there is 3 bars of battery, and a relatable range to 3 bars battery status displayed.

What is going on? Have I recovered lost cells? Should I continue to attempt to run the battery completely down again and see what happens and if there is potentially further gains?
 

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No i-MIEV experience here. But what's likely happened is that the BMS had lost track of the true battery state over time, and pessimistically assumed that the cells had more wear than they really did. By running it down towards "zero", you've reset the BMS's expectations and it now has a better idea of where the true "zero" is.

I wouldn't recommend doing this too often, however. Running Li-ion batteries down too low, too frequently is considered bad for their long-term health.
 

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I ran it down low again, I am not convinced it had a 3 bars worth of battery when I turned it on this morning even though I saw this amazing and apparent miracle with my own eyes. I then slow 3-pin plug charged it to 2 bars at home.

I then went to a public Rapid charger where it had just gone down to 1 bar as I arrived at the charger. Oddly the charger was displaying that single bar left was 14% of the battery. This is normal though, it always has had a larger % display for battery left when down to the final few bars, not sure why. Presumably it is likely something to do with the lost cells I have on the car. 14% per bar x 16 bars = 224% of battery!!

1 battery bar should actually be in the region of 6.25% (16 bars x 6.25% = approx. 100%).

So this rapid charge today - I charged exactly from 1 bar to 9 bars (8 full bars charged exactly, being half the battery), for which I drew 5.25 kW from the charger. That fits in with my previous patterns and estimation of me having 10.5kW of useable battery (based on many previous charging observations).

So the running the battery down low, does not seem to have changed much or have recovered any lost cells, it was a hopeful attempt really. It may have slightly improved the synchronisation of the charging I guess.

Not planning on running it so low any time soon. The car itself does not seem to behave like other I-MIEV's, ION's, C-zero drivers report their cars do, when it comes to battery and charging. For instance, I find the final bar of the battery that gets charged, comes off the display very quickly after heading off. Others report this lasts longer.

I can also always charge to 100% at a Rapid charger without getting disconnected or having to reconnect at any point. The only time this was ever not the case, was when I did about 13 or so Rapid chargers to get the car home from England after I picked it up. Since then I can charge for as long as I want on DC without any need to reconnect, there is no cut off. Probably something to do with being down to just 10.5kW of useable battery.
 
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