2016 Prius 2 Auxiliary Battery Replacement

No, not all the 12v batteries have the same + and - configuration. I don't know about the Gen4 compatible size H4, LN1, or 140R batteries, but for some other size, the + and - posts can be different side of the battery, and some may have battery post on the side or different shapes or connectors. For that reason, the OEM battery will make the change easier.

 

IIRC, the only thing you may need to reset is the electric windows (and sunroof if you have one), same as on any modern vehicle.

 

I was all set to try this 12V battery swap when I read "kitmo"'s post about resetting the electric windows! I don't have a sunroof but do have the electric windows. Now I'm not sure I want to try this. What's involved in resetting the electric windows?

BTW - NAPA has a battery that actually is listed on their site as an exact replacement for the 2017 Prius:
NAPA The Legend Professional Battery BCI No. NA 445 A Wet
Part #: BAT 75140R
Line: NAPA Batteries
Fits your 2017 Toyota Prius

Online Price (USD):
$139.99
/Each

For me this would be the way to go. But today I checked the 12V voltage and it was 12.47V:


I am beginning to wonder why I'm taking this battery out!! The plates were covered but I added a little bit of distilled water, not know exactly how much to add. I have appreciated the replies, especially from kitmo and salamander_king. When I get to the point of actually needing a battery I will take your advice. Thanks.

 

Whenever you disconnect 12v, you may have to reinitialize. Shown below is the page from my 2020 PRIME owner's manual, your model may have them listed on different pages. You can connect the ECU to a battery saver via OBDii port and keep the 12v power connected to ECU while you remove and replace the 12v battery, that will save you from doing the re-initialization as well as losing some saved data such as fuel efficiency and trip data as well as preset radio stations.

But as I said in the first comment, your battery may still have years of service life left in it. All you need is a good battery charger to replenish the SoC and a portable jump pack just in case you forget to close the door and drain the battery down to the point the car needs a jump.

 

I have disconnected the 12 Volt battery several times in my 2016. The only thing I have had to reset is the clock. Don't overthink it...

 

My 2016 2 Eco 12 volt battery (with 5 years and 65,000 miles )died after I left the flashers on about an hour. Fortunately I had one of those small ( a little bigger than my cell phone) jump starters with me and that easily started it right back up. I took a one week trip shortly after that and expected to return to a dead battery, but it started right up with no problem. But, I had it tested 3 ways and they all said the battery was weak. In shopping around online I found that the closest Toyota dealer had the best price at $141, but he was 45 miles away and wouldn't say how powerful that battery was. So the best deal was Interstate (Model MPT-H4) that was near me and lowered their suggested price from $180 to $150. It was 470 CCA compared to the original 295 CCA. I installed it myself after researching some online. There is just one bolt that holds the battery in place. Make sure the car is fully turned off with the drivers window open (just in case). Remove the - terminal first and tie it back out of the way. Then remove the + terminal and lift out the battery. Reverse this to install the new one. I only had to reset the time on the clock, so it automatically saved all the important settings. It was much simplier than I expected.

 

IMHO, the better number to look at, when buying a battery for the Prius, is the reserve capacity. This indicates how long the battery can run under a 25 amp load without dropping below 10.5 volts.

Kudos for doing it yourself though. The stealership always wants a pound of flesh for the simplest things.

 

The official Toyota replacement battery has an 84 month (prorated) warranty. Keep your paper work.

 

Is that 295 CCA value printed on the orig battery? Just curious. I seem to recall 325, but maybe that's just 3rd gen.

"how powerful" is kinda an elusive target. CCA is one factor, but amp hours is also a contender. As one goes up the other tends to suffer. And amp hours is maybe more important? Out of my depth, just a thought.

 

In the hopes some of this info may help others with 12 volt battery issues and questions. It was interesting to see when the 12v gets charged (last bit of this message).

My wife's 2016 Prius 2 Eco got a low 12 volt battery message, and would not start. About 24 hours later, I was able to charge it up with a Viking battery charger, which took about 14 hours! It recovered and ran just fine after that long recharge.

However when I hooked up the charger, it read something like only 0.2 volts in the battery. That got me thinking, this OEM battery has been drained too hard to be trustworthy. As of mid October 2021, trying to get a Toyota replacement 12 volt battery in central California seems impossible - this global supply chain mess is real. I *was* able to locate a compatible Autozone battery, conventional, type H4-DLG. I installed that just like with any other car battery: remove old, clean things up a bit, reinstall the new, the Prius was without battery for probably 20 minutes. There were no problems starting or running, other then resetting the clock and changing the default display on the dash.

What's interesting (to me) is the data from taking voltage measurements on this new battery. It looks to me like the Prius does not charge the 12 v battery all the time. Rather, I suspect that once the voltage gets below 12.4 or maybe 12.3 volts, *then* something gets tripped to start recharging the battery as the car runs. Here's the data I have from my multimeter:

 

My 2016 has 70k miles on it and I have been having intermittent dead batteries over the past two years or so. Since #WinterIsComing I decided to to buy a new one. The dealer had one for $180 and I was unable to find another replacement at Autozone (I called and they said they had no stock anywhere) or other locations (Pep Boys etc) so I went with the Toyota dealer's. I will install tomorrow and see how it goes.

 

Maybe address why they're going off so fast. What's your driving like; is the car often idle for multiple days, short trips?