the OTHER battery

Once that traditional 12-volt battery is deep-discharged, its never the same... just like with non-hybrid vehicles. The plates in that lead-acid solution have corrosion built-up on them now, limiting the capacity available.

Replacement is required.

Identifying the originating cause would be a good idea first. Was there a "forgot the lights on" type of event that you could attribute the damage too? There is always the possibility of a genuine problem, like something draining the battery rapidly (which is not normal, unlike the dealer claim).
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Hello and welcome... I'll just speak for myself. I've had no trouble in the year and a half I've had the Prius. Friends of ours have had a Prius for the same amount of time and have not had that trouble either.

 

As John said, replace the battery & find the problem. The hatch is notorious for not always closing. Lock the car when you leave. It'll beep if a door is open. Disable the SKS if the car is going to sit for a long period. I suspect it is something stupid rather than something major and, no, "Priuses don't do this sometimes".

 

Assuming you have done nothing wrong, Go to the dealer and demand a new 12V Battery! I had problems with mine within the first three months and politely insisted that they supply me with a new free battery. They did this for customer satisfaction. Unbelievably this work could not be done then, about mid-day, as I remember, so they provided a free loaner overnight and I picked up the car the next day. It seems that many cars are off-loaded at the dock and the puny little battery never gets serviced properly. As a result there have been many 12V battery problems. At Priuschat we only hear from the members. In your case, the battery problems should not have gone FIVE times, that is outrageous! Go do it, let us know what happens. One note: In my case, I wanted the old battery, as I'm a battery freak, but Toyota does not let the customer have the old battery. I found thier reasoning for this policy inadequate.