What were the conditions for you getting a battery replaced? My Mitsubishi dealer told me, that I have lost 40% at 70,000mi and they will not honor the warranty unless at least 1 cell is completely gone.
Any suggestion is greatly appreciated.
Several questions: What year is your iMiev? Is the dealer's opinion as to degradation in writing? What test did they do?
Make sure that the dealer gives you both the degradation percent and the test they did in writing.
Where do you live? Average temperatures?
Ask the dealer which battery you have? LEV50 or LEV50N? Get this in writing.
In your case, probably the LEV50 given the degradation. See page 1-5 of the manual for the normal degradation percents after 5 years, etc. Yours is abnormal. Also, the LEV50 were discontinued and should not be installed after 2011 or so. If so, then you should get a new battery.
If an LEV50N is installed, then the degradation should be no more than 10% after 700 cycles with 100% DOD at 113 degrees, based upon the battery specifications. Both battery's detailed specs are posted on this site. You should download both.
If the dealer doesn't cooperate, then request that your case be referred to Mitsubishi Customer Service. See the warranty manual for warranty enforcement instructions, which can be downloaded from the Mitsubishi owners site. Thereafter, you can request binding arbitration, which is the step we are in.
Keep us posted.