My girlfriend inherited a 2009 Prius that was garage-kept and only has 11k miles on it. I put in a new 12V battery, drove it home for about four hours, and it ran perfectly.
But since it sat for so long, I’m kind of worried about the hybrid battery going bad. I don’t know much about hybrids—what are some signs that the battery is failing?
How likely is it that the hybrid battery is on its way out soon?
I’d start saving up for a new OEM battery just in case, but if it’s running fine now, no rush. Also, I’d get a brake fluid flush to prevent issues with the brake actuator. Honestly, might be a good idea to replace all the fluids while you’re at it.
@Evans
Yep, definitely swap out the brake fluid, then do an oil change. And yeah, setting some cash aside for an OEM battery is smart. That thing is basically brand new.
Bell said:
@Evans
Yep, definitely swap out the brake fluid, then do an oil change. And yeah, setting some cash aside for an OEM battery is smart. That thing is basically brand new.
I picked up a JDM 2006 with only 62k miles, and it was in amazing shape, but the hybrid battery was completely dead. Luckily, I had a parts car to pull from.
Get the Dr. Prius app and a Bluetooth OBD adapter. It’s not 100% accurate, but it’ll give you an idea of how healthy the battery is. Other than that, just keep up with maintenance and enjoy it—these cars can go 300k+ miles easily!
Where are you located? I’d check the hybrid battery for you for free just to see that beauty in person. If you’re near Madison, Wisconsin, give my shop a call. 608-729-4082 – EV Powers Hybrid Battery Service and Repair.
@Kelley
Appreciate the offer, but we’re in Maine, so that’s a bit too far. Around here, only Toyota dealerships seem to work on these, so I’m trying to learn how to handle any issues myself.
@Kelley
Do you sell OEM hybrid batteries? My 2013 Prius C is still going, but I think the battery is on its last legs. My MPG has dropped, acceleration sucks even more than usual, and the engine is running a lot harder.
I’m in Madison.
@Chambers
Yeah, but Toyota just jacked up the prices—like 100-130% increases on some packs. It’s insane.
Kelley said:
@Chambers
Yeah, but Toyota just jacked up the prices—like 100-130% increases on some packs. It’s insane.
Update: It looks like the price hike might have been a mistake. I should have a final answer in a few days.
Kelley said:
@Chambers
Yeah, but Toyota just jacked up the prices—like 100-130% increases on some packs. It’s insane.
That’s wild 
@Kelley
How do you actually test a hybrid battery?
Rowen said:
@Kelley
How do you actually test a hybrid battery?
There are different ways to check. Regular folks can use the Dr. Prius app (paid version), but in my shop, I do load testing—charging and discharging under heavy load, watching the live data, and comparing it to known good and bad packs. I’ve been working on hybrids for over 20 years.
11k miles is crazy low. You should easily get another 300k out of it. Like others said, Dr. Prius and a Bluetooth OBD scanner will give you a battery health check.
Since you just did a four-hour drive, did you notice any issues? What kind of MPG did you get?
@Finch
It stayed around 45mpg, but I was cruising at 80-85 when possible, plus some stop-and-go in city traffic.
Pip said:
@Finch
It stayed around 45mpg, but I was cruising at 80-85 when possible, plus some stop-and-go in city traffic.
45mpg at that speed is solid.
Pip said:
@Finch
It stayed around 45mpg, but I was cruising at 80-85 when possible, plus some stop-and-go in city traffic.
Pretty sure you’re in Wisconsin, and I don’t think there are any 80-85 mph roads there… unless you drove out to Montana? Either way, slow down. It’s illegal and dumb.
@Stewart
Lol, it’s a Maine tag. I was coming from Massachusetts, where that’s just normal highway speed unless you wanna get run over. But thanks for the concern 
If it were me, I’d tint the windows to 20% and enjoy the gas savings.
I got over 250k miles out of mine, and it probably could have gone longer. The hybrid battery isn’t crazy expensive, and if it’s working now, I’d just wait until it actually dies before replacing it.
Keep up with full synthetic oil changes and give it a good wax once a year.
Also, I highly recommend this Bluetooth OBD adapter—it connects automatically every time you start the car. I had mine hidden in the console for years.
@Merrick
Does it turn on automatically, or do you have to hit a button? I’ve got one tucked away, but I have to manually turn it on every time, and honestly, I’m too lazy for that.
