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.

 

Here is a question to the true Gen 5 geeks here. Exactly which Gen 5 models have that spare-tire screw hole? I am guessing none of the PHEV models but all of the HEV models perhaps with the exception of the HEV AWD models.

If Mendel or some others ever have to buy a Gen 5, they will have to know.

 

Not that I feel personally insulted, but I have mentioned dozens of times that the battery drain problem appeared at least six months before I added any electrical accessories. Regardless, several trolls have deliberately ignored this fact, and claim that I have caused my own problems. Nothing I have done could possibly cause the type of battery drain I was experiencing.
I have gone to 3 dealers with the battery problem, but none of them could keep the battery from going dead. One dealer even replaced the battery to no effect.
My mods consist of:
A plug in voltmeter.
A live socket wired off the battery, which is for charging my cellphone when the car is off. Nothing is drawing power when I take my cellphone out of the car.
An auxiliary lithium battery, which is fully isolated from the 12V system and can not draw from it, except when I want it to, through the smart isolator. The purpose of the isolator is to prevent accessories from drawing down the main battery.

Everything is working perfectly, and I not the idiot who has caused his own problems as trolls have claimed. I am fairly sure that the wireless updates are responsible for the drain.

 

What are you using for the cut-in and cut-out voltage settings for the isolator?

 

If we can stop the ongoing thread hijacking, can we discuss something useful? (Hint: Gen 4/Gen 5 Prius HEV/PHEV does not have a 12-V battery issue for 99.99% of owners.)

So, all Gen 5 Prius HEV versions, including the AWD versions, have a spare-tire screw hole, but none of the Gen 5 PHEV versions have it.

HEV LE:



HEV XLE AWD:



HEV PHEV:

 

The cut-in voltage is 12.3, and the cut-out id 12.8.

 

I don't know what's causing the drain, and neither do 3 dealers. I'm forced to use a workaround, which has been satisfactory so far.

 

All gen5 HEVs have the spare tire screw hole. No gen5 PHEVs have it. Trim levels don't matter.

The only difference between the FWD and AWD screw holes is that the FWD version is a stand-alone part, while the AWD screw hole is part of the bracket that mounts/protects the rear motor HV connector.