[elhigh]

The grid charger's effect's duration will differ depending on how you drive the car. My wife, when she has the car, returns it to me with the battery absolutely flat. If she has it for a few days in a row, she can cut the charger's effect in half, no joke. If you're gentle on the battery, it'll probably last a lot longer.

My first grid charge made the IMA light go out and stay out for about a month; the second time it was out for about three months. The big difference: winter vs. spring. How it's driven, ambient conditions, all that stuff has an effect on how heavily the battery is called upon, and that, in turn, has an effect on how quickly the pack becomes unbalanced.

When it becomes unbalanced, you rebalance it by grid charging. The batteries that are all within spec charge up first and then just warm up (just a little, nothing to worry about) while the other, lower batteries get dragged up to the same level.

This most recent grid charge has only been on for a week. So far I've grid charged the car about four times. If it keeps the battery in good nick for the next few years, I'll call that money well spent.