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Honda Civic Hybrid 2003 IMA battery getting weak?

My Honda Civic Hybrid 2003 (manual transmission) has been getting worse mileage over the last few months. It works well on the open road, and the IMA battery shows full or nearly full charge much of the time. But in the city, it’s at the bottom much of the time, and I have to down shift to get up even modest hills. It’s the city mileage that gotten poorer. Highway is OK.

However, there is no warning light indicating an IMA problem, and the dealer told me (before the symptom got this bad) that they have no test for reduced capacity. On the other hand, I’ve read that there are codes that indicate battery degradation.

How do I convince the dealer that the battery needs to be replaced? I have less than 50,000 miles on the car, so they should replace it under warranty. Does anyone have experience with the IMA battery failing in less than 80,000 miles?

It is falling within the parameters of the engine computer. Warranty only covers issues. I would just make sure you have your complaints documented. If it fails shortly after warranty expires you can typically get an item covered.

Are you sure the batteries are covered under warranty? After 7-8 years of use?

I thought the life expectancy of these was only 7-10 years. Yes, your batteries aren’t as efficient as they used to be.

Are you using the A/C more recently? That’ll drop your mileage.

The warranty is 8 years or 80K miles, and the car is less than 7 years old (purchased at the end of the year).

Yes, I’m using the A/C, and I’m sure that’s part of the reduction, but the issue is having little or no IMA power to accelerate or go up hills. It is true that the A/C makes a bigger difference in the mileage on this car than on the conventional cars I’ve driven.

Any idea how bad the batteries must be before the dash light comes on? Would the dealer see a code with his computer before the dash light indicates trouble?

Have you read the warranty very carefully? Are you sure it doesn’t just cover a manufacturing defect or complete malfunction?

These batteries lose efficiency over time and are very expensive to replace, that’s why I wouldn’t buy a hybrid, it doesn’t turn out to be very economical in the long run when you factor in replacing those batteries.

How quickly does the battery indicator go from ‘full’ down to nil when you’re driving it? Much quicker than it did when you got it? That would be a good indication of a battery pack with reduced capacity.

Yes, the battery is stuck down at minimum much of the time in city driving. It used to hover around half or three quarters, depending on the driving conditions. In the city, it’s seldom over 3/4–after coming a long highway hill, for example, and down to zero within a mile of driving after that. It never used to behave this way. Although it’s been gradually getting lower, there was a sudden change in behavior less than two weeks ago.