Recently, my Check Engine and IMA Check lights both came on. My Honda garage tech advised me that the code revealed “Battery Deterioration”. The code was cleared and when the car was restarted both lights had gone off and have not come back on…yet (10 days ago). Eventually, I know the lights will reappear and I will have to commit (or do I?) to a new battery. The battery installed would run about $2500 dollars. A question occurs to me now that didn’t when I was at the garage. Would that car function normally without the IMA? I know the mileage would drop but would I still be able to drive the car?
What warranty came with this car? I thought the battery pack had an 8 year warranty.
Not all of the battery cells may need replacing. Only replacing the bad ones would be cheaper.
You are correct about the battery warranty. 8 year or 80k… mine has 87k. No mention was made (so far) of the feasibility of replacing only defective cells.
Well hey, if they want to replace ALL of the batteries instead of just the bad ones under warranty then let 'em, yes? 
My experience is that Honda is no longer offering a good will warranty for cars that are outside by either miles or time.
If you google for hybrid battery repair you’ll find a few options out there. There is at least one business who is offering upgraded cells for the batteries, they’re supposed to be less sensitive to heat and last longer. Even with the upgraded cells you would be below the $2500 from Honda.
Whether or not your car will run properly without the hybrid battery is in working order sort of depends. The way the IMA system works you may actually get better mileage however I find that in my Insight that without the extra boost from the electric motor the car is just pathetically slow.
In addition sometimes a bad battery will cause the generator to always be in background charge mode, this means that there is a large drain on the engine whenever you are driving as the generator tries to charge the battery.
Lastly, sometimes when the computer shuts down the hybrid systems due to a bad battery it will also cause the car to stop charging the 12 volt battery under the hood. When this happens it is just like your alternator is bad in a regular car and eventually the car will just stop running because everything needs electricity to run.
I know of one business which has developed a circuit board that they offer as a loaner while they have your battery for rebuilding, this board makes it so that you can drive your car without the battery in there and other than being slower should have no other effect.
FYI, I paid $800 to have my battery pack “rebuilt”. I could do it myself with instructions available on the net but the sticking point is that I’d still need to find replacement battery sticks for the bad ones. These are getting harder to find as battery pack rebuilders are quick to snap up junkyard packs.