[northbridge]

here:

My dealer took a 2000 Insight 5mt in trade earlier this year which needed a battery replacement. I looked at the car initially while they were waiting for the new battery pack, then they replaced the battery pack, and 3 days later I was test driving the car with the new pack. They said the service bill was around $2500 total, parts and labor. 3 days and $2500 for a repair on a 10 year old car is not out of the ordinary. I wouldn't hesitate to buy a hybrid.

http://www.crzforum.com/forum/engine-battery-discussion/14-replacement-cost-battery-4.html

That thread has a bunch of conflicting information about prices and repairs but the general concensus is that the battery should last a long while.