Basically you got about 100 D cells in your battery pack arranged in tubes of 6. They are hooked in series like the police edition of the mag light that takes 6 d cells. All it takes is one bad cell to cause problems. Thats what has happened. It limits the effectivness of the whole pack and once its down to 10% or half an amp vs 6.5 amps it generates a code. It usually generates a hell of a lot of heat and you get a thermal code too.
Grid charging for an extended peroid of time restores the charge to the 100+ batteries that make up your pack. As it wears they all discharge at different rats do to variations in manufacture and internal resistance and the price of tea in China.
I own a gen 2 insight with 84 cells. It can take 36 hours to balance the pack. It takes 4 months of driving it like a rental car to make them start to wobble. I drive daily and at least 3 times a day.
If you like the car and are handy, you can buy an aftermarket battery for less than 2 grand depending on vendor. Just think of it as buying a tranny or engine for a non hybrid vehicle.
