My 2007 prius requires frequent jumping of the Aux Battery.

If the battery is five years with multiple discharges to the point that the car won't start it probably needs to be replaced, even if something else is causing the discharge. I replaced mine with the Optima battery at 4 1/2 years when the voltages were marginal, before I had any real problems. It is possible that the original battery was not charged properly when the car was serviced prior to delivery, which could have caused the original battery to die off prematurely.

I'd replace the battery first and then see if you are still having problems.

 

This is an old post. The new BBS software has unearthed many old threads, so please check the dates before replying.

Tom