Auxiliary battery on Toyota Prius 2001 and Toyota Prius 2004 fail if the car is not driven at least every 7-10 days. This prevents the car from starting. We purchased a 2001 Prius used March 2004, and a new 2004 Prius in June 2004. The auxiliary battery failed on the 2001 Prius twice, and we replaced it once. Recently the dealer service rep told us that it is a known problem that the battery will not hold a charge unless driven every 7-10 days, and should be "disconnected" if parked for "prolonged time." This is potential safety problem for car not starting, such as if returning on plane after 2-3 week vacation and not being able to start the car, risk for vulnerability awaiting jump start. Toyota's only response is "well, it's a hybrid." They say the "hundreds of computers in the car drain the battery when parked." They could have designed in some automatic or simple switch to address this. They also could notify the potential customer of this design flaw. They did not inform us, or any of the other Prius owners we have recently discussed the issue with. The owner's manual for 2001 model makes no mention of it. In the 2004 manual, there is a brief mention of need to disconnect the battery if parked for "prolonged time" but does not define that. Although we have been happy with other features of the Prius and other toyot as we owned in the past, we consider this to be a serious and risky design flaw. Furthermore, we consider Toyota's sales people and sales brochures failure to notify us of this problem to be a significant breach of goodwill and respect for customer safety and satisfaction.

- Roseville, CA, USA

My car (2001 Prius) was at a dealership (marina del rey Toyota) for service. While parked, with no one inside and the ignition off, the main propulsion battery caught fire and burned through the vehicle interior, causing a total loss. Toyota blames the fire on a battery defect.

- Culver City, CA, USA

Vehicle stalled/died, and lost power while driving 5 mph. Throttle body module failed. There was a NHTSA recall but this involved a chemical in the pruis car battery. L. yes. Car has broke down several times since. The stalling is still a problem.

- Atlanta, GA, USA

After sitting for as many as 2 days without driving, there is a battery failure. This has occurred on numerous occasions (8-10 times), and the dealer has sent a tow truck out to either start the car or tow the car into the dealership. At one point, the car was in the dealership for 3 weeks while they worked on solving the problem. They have put in several new batteries, but the problem continues. The latest occasion was this past week (October, 2002). I was without the car for 3 days. No problems were found at the dealership except for battery failure. In the past the dealership has provided me with a battery charger, but the battery charger is currently not working properly.

- Louisville, KY, USA