I also have a 2003 Civic Hybrid. At about 70,000, the IMA battery struggled to stay above 1/2 charged. My gas milage dropped,especially around town to about 26 - 28 mpg. I brought the car to 2 different dealers, and one said the condition is normal for a battery this age. I asked if I came in with worn ball joints, would they say the wear was normal for the milage? No arguing made and difference.
The car now has 83,000. Condition is about the same. Almost never above 1/2 charged. This causes the engine to constantly charge the battery, not just down hills or when braking, all of the time. If the charge gets up to 3/4, just a couple of uses of the assist causes it to drop to half or less. In various city driving conditions, I ran out of IMA battery completely.
The battery issue, along with constant transmission bucking (transmission was replaced once at 46,000 miles) makes this car a potential disaster. My only hope is that the battery will fail completely before my extended 100,000 mile warranty expires next year.
While I saved quite a bit on gas in the early days, especially when I was driving 100 miles/ day, if you consider the overall cost of paying an extra $2,500 initially for the car, and potentially $3,000 for a new battery, I could have bought a regular Civic (my wife has one), that gets good milage, (30 highway, 20 something in the city), I could have drived the first 66,000 miles and not spent a dime on gas for the extra costs of the Hybrid if you use an average cost/ gallon at $2.50 for my 6 years that i owned this car. Now, my Hybrid gets only 2 or 3 mph better than my wife’s Civic in the city. Highway, where you don’t use the Assist very much, the Hybrid still gets about 40 mpg.
I would really think hard about buying another Hybrid.