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Prius starting battery drains easily

I have a 2005 Prius, bought used in 2007. I like to sit in my car, when I have to wait somewhere, and listen to the radio. But recently, when I do that, the battery goes dead and I have to get a jump. I open the door and close it to make sure the headlights are out. The only thing using battery power is the radio, as far I can tell.

Shouldn’t the battery be able to support 45 minutes of radio with the engine off? Anyone else have this problem?

With such a heavily gizmoed car as the Prius, I wouldn’t rule out that some high-draw electrical thingee comes on when you play the radio, but since the problem recently developed, I’d say your problem is almost certainly a battery on it’s way out. It’s just a regular old 12v car battery and if it’s the original one, it’s probably 4 years old and at the end of it’s useful life.

This actually poses a good question. Does the Pruis’s electric motor run the alternator and recharge the regular 12v battery? Maybe if you are in economy mode, and not using the gas motor much, you could run the 12v battery down.

If that is the OEM battery, it is just time to replace it. Many batteries last no longer than that, although some will last twice as long.

The Prius has two battery systems. The primary battery system is the large nickle-metal hydride battery that is used for the hybrid system. I believe that battery uses a different voltage potential than the standard 12V. The rest of the car uses a standard 12V system, and it uses a very small 12V battery located in the rear driver’s side fender well. This small battery is used to ‘power-up’ the ECM and hybrid system. Since this car does not have a typical starter system, this battery is more like a lawnmower battery. The hybrid battery is what starts the engine. This car does not have a typical alternator either, but gets the 12V power and small battery charged through a power transformer attached to the hybrid system. Simply put, you cannot run the radio off battery power for long. The 12V system doesn’t have the power storage capacity of the typical car. I’m pretty sure such things are mentioned in the owner’s manual.

This brings up a point. No one has posted to ask, “How can I give some needful driver a jump start with my Prius?” Maybe, the Prius battery has enough oooph to give a jump start to car which needs just a small assist (amperage and voltagewise), if the Prius hasn’t had it’s battery run down.

“I’m pretty sure such things are mentioned in the owner’s manual.”

The Owner’s Manual has justly been called “The least-read best seller in the world”. I have essentially given up on assuming that people will read this incredibly valuable resource that sits in their glove compartment.

Thanks for the rundown BK. I don’t own or plan to own a hybrid in the near future, but still like to keep up on current automotive technology.

The 12 volt battery is probably needing repacement. It is NOT a standard 12 volt battery. It’s a different technology than regular car batteries, and is a strange size. It’s not a lawnmower battery. It costs over $150.

While you could jump another car with a Prius, the owner’s manual says not to. You can, however, jump a Prius from another car.