Where Is The 12V Battery On A Gen5 HEV?

For what it's worth, I had a maintainer on my Gen 3, and a few times it failed to keep the battery up.
At first, I blamed it on a faulty maintainer, but later I learned that the alligator clips are unreliable. They tend to lose connection over a few weeks. That's why I connected my current maintainer through ring terminals.

 

I had a NOCO Genius 3 for over a year, with zero problems. Before that, I had tried several brands that were less reliable. They kept turning themselves off, and I got tired of having to open the hood to check all the time.

Recently, I upgraded to a NOCO Genius 5 so that I'd have enough power to keep the 12V cooler running while I was parked and plugged in.

When I did the upgrade, I took a shortcut, using the old wiring harness, which had a 4A fuse, which finally blew. I upgraded the fuse, and all is now well.

 

I’m using CTEK, they’re getting pricey though.

 

without knowing anything for sure, 2A should be plenty to compensate for any drain.

 

Maybe you've said it before, but are you going to be leaving your car sitting unused for a week or more on a regular basis? Or are you only going to be doing trips of 10min or less with no longer trips for weeks at a time?

If the answers to both those questions are no, you almost certainly don't need a maintainer. If the answer to either one is yes, you might need one. If the answers to both are yes, I'd say a maintainer would be a pretty good idea.



I'd also take Paul's advice with a small grain of salt for two reasons. First, he owns a Prius Prime where you're getting a regular Prius. Primes are a little more susceptible to draining their 12V batteries because of the added monitoring of the HV charging system. There's been a TSB and software update about it that has helped things, but Prime owners have been having 12V battery failures at a higher rate than regular Prius owners.

Secondly, Paul's car is far from a typical use case. He's added a bunch of stuff to his 12V system that you won't have on your car. Setting aside completely whether those changes were wise or not, it does mean his car is not going to behave the same way as your car will. I'm not saying to ignore his advice or anything, just saying to view it through the proper lens. What's needed in his case might not be what's needed in yours.

 

I can only speak from experience. 99% of the time, the maintainer does its job, and the battery is good. But it can drain very quickly at random times, so I always carry a booster pack.

 

I thought you were using a hand-cranked one, Mendel, like your tire pump.

 

Just for the record, nothing added to my car can cause excessive battery drain.