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Prius 12v Battery Issues

prius 12vbattery issues

Do you have Prius 12v battery issues? IS MY 12V BATTERY DEAD? 

Some of the symptoms of a dead or dying 12v battery are:

  • Can’t unlock the car with key fob (if this is your only issue check battery inside the key fob)
  • Car won’t start or lights flicker
  • Dim headlights/dome lights
  • Windows roll down slower than usual
  • Trunk won’t open
  • Message that says, “Park your vehicle on level ground and apply the parking brake.”

Here’s a video showing how to check your 12v battery from the display. Obviously you can only do this if you’re able to power into ready mode.

If your car is locked you will need to access the emergency key located inside your key fob. Here’s a photo to show you where to find it.

hidden emerg key




If you connect the jumper cables backwards, the main fuse will blow. A reverse polarity jump can cause harm to the DC/DC converter.  RED IS POSITIVE + AND BLACK IS NEGATIVE –

If you’re stranded in an area where you don’t feel safe, leave. Your car is not worth your life. Call your insurance company and see if you have roadside coverage or call a local tow truck.

You can jump start a Prius like any other car, but there are some things you should know before starting. Most Prius 12v batteries are located in the trunk on the passenger side (with the exception of the Prius C which is under the back seat and the 2016+ Prius which is under the hood). Luckily, Toyota added a second jump point in the fuse box under the hood of the car.

How to open the hatch if the 12v is dead-Click Here

If you’re unable to access the battery in the trunk or prefer to jump from under the hood you can do this by first locating the fuse box.

Inside the fuse box you will notice a red cap with a + sign. Under the cap is a metal plate that will act as your positive terminal (where you connect the red cable to). There is no dedicated negative terminal, so just connect the black cable to a nut or bolt under the hood that is not painted (should be bare metal).

negative ground 1
negative ground 2

When all cables are connected you should hear a faint clicking sound and be ready to turn on your car. If this doesn’t work, try adjusting the position of the cables on your vehicle. Sometimes it can take a few attempts.

My biggest recommendation is to always carry a portable jump box like this one We can’t always rely on someone else to be around to lend their car to jump with.

Buying a new 12v battery

If you think your 12v battery may be dead, you can take it to a local auto-parts store like AutoZone. They can perform a load test to determine if it needs to be recharged or replaced. There are several aftermarket brands of 12v battery that will work for your Prius, just call ahead with your VIN to check if the parts store has the correct one in stock. If you’re ok with paying a little more, the Toyota dealership has OEM batteries which may provide extra longevity.


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