I purchased my 2005 HAH in late 2005 new. I have 124K miles on it, and the dealer service shop told me that the reason for the IMA and engine light that just came on is that the IMA batteries are deteriorating. Replacement cost quoted is over $2600.

My position is that this cost offsets all fuel savings I have had in the 8 years of owning the vehicle, so if I do this the whole point of owning the hybrid is defeated. I am also unlikely to own the vehicle long enough to recoup this cost in terms of future fuel savings, due to declining gas mileage and just economic reality. I asked the dealer service advisor about the consequences of driving without replacing the IMA battery and he did not know much.

I saw a reference in other posts about this but it was pretty vague. Other posting are clear that you cannot just remove IMA components. I guess one concern is the role of the IMA as a replacement for the alternator, and whether reduced or little battery capacity would ultimately cause problems elsewhere.

Any ideas or direct experience from other owners?

 

I also guess that the long term presence of the engine light due to IMA battery problems could mask other more serious issues that would trigger the light.

 

New user here.

2006 Accord Hybrid. 161,000 miles.

My IMA light and check engine lights came on at 136,000
Took the car to the dealer. They found that one of my coils was fried, and according to them, the wrong spark plugs were installed in my car. Replaced the coil, installed very expensive spark plugs. Then they call me to tell me that my IMA battery is bad and needs to be replaced at a cost of almost $2500. I could not afford that, and said sorry, but no thanks.

The light, both IMA and check engine will go away, and sometimes not come on for a week or two, then it will come on for a day, sometimes a few days and then as quickly as it appears, it disappears again. My assist seems to work and turn on when it needs to, and the battery bars go up to full and then go down as the assist uses the battery up. Auto stop kicks in about 95% of the time when I stop and have my foot on the brake. The other 5% of the time, I may be stopped and the car does not autostop.

Don't know if I should keep driving as it is, if I am risking some terrible result or not. What happens when the battery really does go bad does the car not run any longer? Once, a couple of years ago, my regular 12v battery died in the parking lot of Walgreens. I cranked and nothing. With the ignition switch still in the run position, I put the car into drive and when I stepped on the gas, the car moved, silently, though not fast, and I was able to drive about 1/4 of a mile, to a discount auto parts, where I replaced the 12 starting battery. I did not know it was even possible for our cars to move with just the hybrid battery pack. Don't know if it was a fluke or a malfunction, but I never have done that again.

 

To my best knowledge of understanding how HAH works, I can tell you the following.

In theory, there is only a slight chance that the IMA battery will completely fail not maintaining a 144V charge.

Unfortunately this is the weakest link. HAH requires the IMA battery to charge your 12V battery, maintain the electric A/C compressor running, keep power to the IMA ECU (located in the truck close to the IMA battery) and even the electric power steering.

So as you can see...driving with the IMA light on and even if the IMA system doesn't work no more...in theory having the V6 engine driving the car will NEVER post a problem till the 144V IMA battery goes on you. That's the day your HAH will not work anymore.

The 12V battery only powers everything when your car is not started...and also to start your HAH if IMA system doesn't work for whatever reason and/or very cold days when ECU detects it is too cold to start with the 144V IMA battery.

As long as 12V battery is still holding a good charge, you can still start your HAH daily and drive without issues...you loose all the fuel savings plus the dead weight of the IMA battery but it will work.

Like I said it will only work till the IMA battery cannot hold the basic 144V charge and load anymore. If the IMA battery is dead and not holding charge, it will not charge your 12V battery anymore killing this sorry little battery too. Then RIP to HAH still IMA battery can be replaced.

System will function 100% again if IMA battery is replace....

Hope that answer your question.