Prius Generation 2. -
1) A common problem we see in this model is the throttle body sticking. Leads to poor performance and poor fuel consumption. Freeing up the spring mechanism fixed the problem.
2) Vehicle starts up stutters then stops. The cause could be carbon built up in the exhaust. Blowing the exhaust system out may fix the problem. Another cause could be excess oil in the throttle body. Can be seen if you remove the air filter. Pour some petrol down to dissolve the oil and start the vehicle. This may solve the problem. Oil deposit was caused by excess oil in the engine from overfilling.
All the above problem will affect the battery causing it to fail. Proper servicing from knowledgeable technicians about hybrid vehicles will save money in the long run.