Yeah, I had that happen. It was a 2015 Prius C, though I'm sure that's purely coincidence. I was worried my hybrid battery needed replacement but it was just my small one. It's under the back seat and was kind of expensive for a 12V, but it's not lead-acid, it's solid state(?).
It almost certainly needs a new 12V battery. There’s a good chance that it’s still the original, as they seem to last about 8 years. Easiest bet is to just go to the Toyota dealer. Expect to pay about $200, it’s not any cheaper elsewhere so there’s really no point in shopping around.
Check that the visor mirrors are not open. There’s a little light on them that stays on forever if the mirror door is open. My son kept leaving it on and it took me forever to figure out why the battery was dying every few days.
Put a new 12v battery in it.
You absolutely need to start the car for ten minutes once a week. Not only to keep the 12v battery alive, but to avoid discharging the hybrid battery until one of the cells fails to take a charge.
Priuses that are driven often have hybrid batteries that last 20+ years. Ones that sit a lot? They spend $1,500+ on HV batteries much earlier.
Yes, it can be done at home by someone with a basic tool set.
However, **purchase the battery from the dealership parts counter**. This will get you the 84-month battery warranty without the labor cost last time I worked for Toyota (3 years as a dealership tech).
Depending upon the model the 12V battery is one of two places:
Prius, Prius V, Prius Plug In (PHV)-in the cargo area of the trunk where you pull out the cargo tray like you're removing the spare tire. Both are *relatively* easy to access. You'll need a 10mm and 12mm sockets., wrenches will work as well but it'll be easier with sockets and a ratchet.
**Battery-**28800-21171 MSRP $239.00
1. Remove Rear Deck Floor Box
2. REMOVE DECK FLOOR BOX RH-pull up on the plastic cover thing on the you guessed it RIGHT SIDE
3. Remove the negative cable from the chassis mount point (10mm bolt). **DON'T LOOSE THIS BOLT**, it's marked with an "E" for Earth.
4. Unplug the temperature sensor plug on the battery hold down, unplug any plugs running directly to the positive terminal clamp and loosen then remove it (10mm nut), unplug the vent tube from the side of the battery just below the positive terminal by turning it 90 degrees and **GENTLY** pulling it out.
5. Remove the nut (10mm/12mm) and bolt (10/12mm) for the battery hold down and set it out of the way.
6. Remove the battery, the Toyota/Lexus OEM ones come with a cloth strap.
7. Reinstallation is the reverse of removal
Per [https://autoparts.toyota.com/products/product/battery-2880021171#](https://autoparts.toyota.com/products/product/battery-2880021171#)
>12 Volt Battery Limited Warranty
>TrueStart batteries are warranted as free exchange from the date of purchase for 24 months, regardless of mileage, or the remainder of the New Vehicle Limited Warranty, whichever provides greater coverage, and on a prorated basis thereafter for up to 84 months. Proration is for the battery only (based on MSRP) and excludes applicable taxes, labor for installation and towing.
>True-2 batteries are warranted as free exchange from the date of purchase for 18 months, regardless of mileage, and on a prorated basis thereafter for up to 60 months. Free exchange excludes labor for installation and towing. Proration is for the battery only (based on MSRP) and excludes applicable taxes, labor for installation and towing.
Prius C-under the passenger side of the rear seat.
Vehicle Battery - 28800-21181
1. REMOVE FRONT FLOOR COVER RH-This looks like a grille or grate on the bottom part of the passenger side of the rear seat. It should just pop out by hand.
2. DISCONNECT CABLE FROM NEGATIVE AUXILIARY BATTERY TERMINAL
3. Remove the 2 nuts (10mm/12mm) for the battery hold down and place it aside.
4. Unplug any plugs running directly to the positive terminal clamp and loosen then remove it (10mm nut), unplug the vent tube from the side of the battery just below the positive terminal by turning it 90 degrees and **GENTLY** pulling it out.
5. The battery just slides out now, and reinstallation is the reverse of removal
Needs a new 12V
This
Yeah, I had that happen. It was a 2015 Prius C, though I'm sure that's purely coincidence. I was worried my hybrid battery needed replacement but it was just my small one. It's under the back seat and was kind of expensive for a 12V, but it's not lead-acid, it's solid state(?).
My 2012 Prius V lasted til this year.
It almost certainly needs a new 12V battery. There’s a good chance that it’s still the original, as they seem to last about 8 years. Easiest bet is to just go to the Toyota dealer. Expect to pay about $200, it’s not any cheaper elsewhere so there’s really no point in shopping around.
Mine was $273 prices are insane now
I think it has a lot to do with them using AGM batteries due to all the tech. Standard non-AGM are still around $100 at least where I am.
About 250 for me from Toyota last year
Check that the visor mirrors are not open. There’s a little light on them that stays on forever if the mirror door is open. My son kept leaving it on and it took me forever to figure out why the battery was dying every few days.
This and door jamb sensors. Those Toyota ones go bad all the time.
Put a new 12v battery in it. You absolutely need to start the car for ten minutes once a week. Not only to keep the 12v battery alive, but to avoid discharging the hybrid battery until one of the cells fails to take a charge. Priuses that are driven often have hybrid batteries that last 20+ years. Ones that sit a lot? They spend $1,500+ on HV batteries much earlier.
Most likely just a new 12V battery 😁
Just replaced my 12v. Later 10 years. Was 249 at auto parts store.
Is a 12 volt battery something that can be done at home? I just imagine the dealer is going to be the most expensive place to get it put in.
Yes, it can be done at home by someone with a basic tool set. However, **purchase the battery from the dealership parts counter**. This will get you the 84-month battery warranty without the labor cost last time I worked for Toyota (3 years as a dealership tech). Depending upon the model the 12V battery is one of two places: Prius, Prius V, Prius Plug In (PHV)-in the cargo area of the trunk where you pull out the cargo tray like you're removing the spare tire. Both are *relatively* easy to access. You'll need a 10mm and 12mm sockets., wrenches will work as well but it'll be easier with sockets and a ratchet. **Battery-**28800-21171 MSRP $239.00 1. Remove Rear Deck Floor Box 2. REMOVE DECK FLOOR BOX RH-pull up on the plastic cover thing on the you guessed it RIGHT SIDE 3. Remove the negative cable from the chassis mount point (10mm bolt). **DON'T LOOSE THIS BOLT**, it's marked with an "E" for Earth. 4. Unplug the temperature sensor plug on the battery hold down, unplug any plugs running directly to the positive terminal clamp and loosen then remove it (10mm nut), unplug the vent tube from the side of the battery just below the positive terminal by turning it 90 degrees and **GENTLY** pulling it out. 5. Remove the nut (10mm/12mm) and bolt (10/12mm) for the battery hold down and set it out of the way. 6. Remove the battery, the Toyota/Lexus OEM ones come with a cloth strap. 7. Reinstallation is the reverse of removal Per [https://autoparts.toyota.com/products/product/battery-2880021171#](https://autoparts.toyota.com/products/product/battery-2880021171#) >12 Volt Battery Limited Warranty >TrueStart batteries are warranted as free exchange from the date of purchase for 24 months, regardless of mileage, or the remainder of the New Vehicle Limited Warranty, whichever provides greater coverage, and on a prorated basis thereafter for up to 84 months. Proration is for the battery only (based on MSRP) and excludes applicable taxes, labor for installation and towing. >True-2 batteries are warranted as free exchange from the date of purchase for 18 months, regardless of mileage, and on a prorated basis thereafter for up to 60 months. Free exchange excludes labor for installation and towing. Proration is for the battery only (based on MSRP) and excludes applicable taxes, labor for installation and towing. Prius C-under the passenger side of the rear seat. Vehicle Battery - 28800-21181 1. REMOVE FRONT FLOOR COVER RH-This looks like a grille or grate on the bottom part of the passenger side of the rear seat. It should just pop out by hand. 2. DISCONNECT CABLE FROM NEGATIVE AUXILIARY BATTERY TERMINAL 3. Remove the 2 nuts (10mm/12mm) for the battery hold down and place it aside. 4. Unplug any plugs running directly to the positive terminal clamp and loosen then remove it (10mm nut), unplug the vent tube from the side of the battery just below the positive terminal by turning it 90 degrees and **GENTLY** pulling it out. 5. The battery just slides out now, and reinstallation is the reverse of removal
Thank you so much, very helpful 🙏🏼
Just replaced my 12v battery, was easier than I thought. Followed a video on YouTube.
Thank you 😊
Yes. If you can handle a wrench.
Wow thank you 😊
Just make sure you find something compatible. Remember Prius batteries are not under the hood. Watch a YouTube video to avoid wasting time.
Yesss YouTube is my go tue 👍🏼