To really know what's going on with your battery, you need the CANION app and the recommended OBDII port connector. Then you can see the charge/discharge levels of each cell in the battery along with battery temps. A proper balancing of the pack is critical. If the CANION shows levels out of balance after a full charge, then you need to do full charges until they do. It is also advisable to monitor cell voltages at a complete discharge (down to turtle) and look for weak cells. The amount of usable energy in the pack to drive the car is determined by the weakest cell--the first to reach cutoff voltage. The battery management system (BMS) hides the degradation of the pack from the user. With CANION you can see (as the pack ages) the BMS allows the pack to use more and more of the pack capacity by allowing the weaker cells to discharge further. Although there is not much capacity in the lower voltage regions of the cell, it is enough to allow the stronger cells to keep the I-MiEV traveling nearly as far as it did when new. If the battery is disconnected, controllers reset etc., there is still embedded things in the BMS that cannot be changed. Figured into the algorithms that run the BMS are things like the date the pack was assembled. Also, there is a complete history of charge and discharge cycles. This algorithm is part of a pre-determined curve for the battery life of the pack and is one of the things that allows for a change over time of the lower limit the cell voltages can reach before shutdown. Owners of older I-MiEV's should see a fairly rapid loss of range after the first cell in the pack reaches the absolute lower limit of cell voltage allowed by the BMS.
That being said, to keep the pack healthy and delay the onset of real range anxiety, there are a few things you can do--all of which have been discussed on this forum before. First, drive and enjoy the car but be aware of the limitations of the battery. Hot cell temperatures and a high charge level are about the worst thing you can do to a Li-Ion battery. Next, is having a pack out of balance. If you don't need all of the range of the vehicle, don't charge it fully. If you need full range, try to finish the charge just before you need to drive. This will limit the time the pack "soaks" at a high charge level. Try to recharge at night when it is cooler and after the cells have had a chance to cool off on their own. This will minimize the heat buildup in the pack. If it is very hot out, a little box fan placed in front of the car will help cool the charging system and to a limited extent, the pack itself. There is a radiator under the hood that cools the invertor, motor and charger by liquid cooling. For some reason (unless very hot) the radiator fan doesn't operate during charging. The components of the charging system run much cooler with airflow through the radiator and the pack enclosure gets some external airflow which in a small way will help. To keep the pack in balance, it is very important to let the balancer system work from time to time. Again, let it complete the charging and balancing just before you need to drive, and with a CANION as a guide, you can determine when the pack needs balancing. Going to partial charges, or shutting off the charge cycle before the vehicle does it on its own (even if all bars are showing) does not let the balancer do it's job. This is most likely the next most important thing beyond temperature and charge level control to keep a battery healthy. If you have a Chademo or cold weather package equipped car, do the A/C into the pack mod by removing the servo motor connector and the motor itself from the floor vent and place the damper into the position that directs air into the pack. This works in summer to cool the pack and in the winter provides heat to the pack. Heat kills these batteries. They are happiest being stored at 77 degrees. The calendar life degradation of the battery cell really picks up above that temperature. In summer, try to park if possible in the shade. Not so much for the interior temps of the car but so the area on which you park the car (like asphalt parking lots) isn't a hot as a frying pan and radiating heat into the pack located inches above it while you park. If you are not going to drive the I-MiEV for several weeks, try to park where the temps will be 77 or lower if possible, have the car at 50% or less state of charge and put a battery tender on the 12v battery to allow it to power the various "always on" systems in the car without killing the battery. If you have no way of powering the battery tender, you could use a small solar panel to do the job or just disconnect the 12 volt battery.
It's a lot of stuff, but a few small things will make the time the range starts to fall off (and it will) happens months or years later then if you didn't take these few steps. There are other issues with the I-MiEV that need to be watched if you want to drive it until the end of time but the battery health should be the number one priority. So, as to the "dealer improves battery!" topic, there is nothing that the dealer can do that you cannot do by just following some simple things. Beyond bringing a pack into balance, you cannot reverse any other things that may have shortened the life of a cell. However, you can limit further damage. Happy motoring!
