Check 2007 Prius 12V Battery

The Prius has seemed to be running the hybrid battery low quickly, and then charging quickly as I drive. It’s just a feeling I have from driving this car for 3 years. I posted a note on Prius Chat and someone suggested that my 12V battery might be low, which wasn’t something I suspected. I thought I might have defective hybrid batteries.

So I ran a quick check by turning on ACC mode (press power, no brake) and opened  the windows. Sure enough, they were really, really slow to go down. I then found this procedure as well:

Get your Prius into "Accessory Mode" - Press the power button without touching the brake pedal.

Put the MFD into "Maintenance Mode" - Press and hold the "Info" button on the MFD while turning the headlights on and off 4 times.

Press the "Menu" field on the screen.

Press the "Display Check" field.

Press the "Signal Check" field.

The 12v battery voltage will be one of the items listed, it should be above 12 volts. If it is lower, either the battery needs replacement or the charging system is not functioning correctly - see step 7.

Put a small load on the battery by pressing the power button again without touching the brake pedal. The voltage should stay above 12v. If it drops significantly, you need a new battery.

My battery was reading 10V, so a replacement is needed. I called the local Toyota dealer and they have them for $174 in stock. A bunch of online places have recommended eLearnAid for low prices, but their sale is $165 (list $240). I guess Toyota realized it’s not worth overcharging for parts.

So I’m off to get a new battery.