12V battery going dead

good move

 

You probably won't listen to this either, but there's no wiring going into the battery itself. There's no sensor or anything like that. There's the negative terminal that has a second lead bolted to it, the positive terminal under the red cover that has two leads going out, and the battery hose on the side that directs any hydrogen or hydrogen sulfide out of the car's cabin. You can replace the 12V battery with any H4 sized battery, though some choices might be better than others(this is not known as fact, only theory).

Options:
1. Toyota TrueStart H4 470 - Part Number 00544-H4052-470
- this is the Toyota-specified replacement battery; cold cranking amps are increased to 470A from the 285A in the factory battery
2. Any other H4 flooded battery that's at least 285 CCA and has a side port for a battery hose
- it's a theory that the car's computer expects a flooded battery, so the charging profile is likely configured for that
3. An H4 AGM battery of at least 285 CCA
- for those that want an AGM battery and think the car is programmed well enough that swapping in an AGM won't hurt it
4. An H4 lithium battery of at least 285 CCA
- for those that want to spend even more for almost no gain

 

Solution offered that would be far less cost than a custom retrofit involving a controller and extra battery. However if you want a custom solution many could build one for you.

Yours was considered.

This could be the foundation of a custom solution. However the batteries have to be isolated during shutdown states and properly connected during charging states. Ideally the backup battery would be isolated from the primary when needed to carry the startup load to avoid dropping voltage to the discharged primary.

It could be done with a slightly revised scenario such as employed for rv’s with a primary start battery and a secondary rv load battery using a battery isolator. Your situation needs to switch loads on demand.

Opinion:

I get it. Bought a new car, possibly paying $1,000 a month or more for six or seven years, the honeymoon phase is over and the car requires regular jump starts due to an undefined parasitic draw. I would be angry as well.

Realistically Toyota needs to find a solution (possibly have) and implement across all impacted vehicles.

Historically Toyota has done so on a wide range of Prius problems with simple software updates to complete engine rebuilds. Your time will come.

 

Toyota celebrates customers who don’t complain

 

Ha ha, well said, yes!

 

First of all, you thought there was something magical about having a large traction battery that could juice up the 12-V battery and eliminate all these problems. What you didn't realize was that, in a regular car, the traction battery is replaced by the alternator, and it is exactly the same thing. Once the car starts, the traction battery or alternator juices the 12-V battery. If the car doesn't start, then you need a jump start. So, everything is the same. Having a traction battery does not eliminate the need for a jump start, as you still need to start the car electronics, which requires tens of amperes.

Now, we can argue back and forth on whether the minimum starting current for the Prius is 50 A or 30 A or 10 A, but the point is that you still need a sizeable second 12-V battery. And that would come with its own circuit, cables, fuses, electronics, switches to isolate it when the main 12-V battery is healthy, etc. That is just way too much complication and not a practical solution that Toyota or any other company would approach. Much more practical solution: carry a booster pack in your car if you are prone to frequent dead batteries.

Coming back to your actual problem, when you just said that Gen 5 Prius required a special battery, it showed how little you knew on this subject. These are the only two requirements:

• Size: EN LN1 or BCI 140R or DIN H4 (three entirely equivalent sizes)
• Center-vented with two holes and a plug to plug the unused hole, with the other hole to be connected to the exhaust hose

I am pretty sure that you have a bad battery. You may have some other problem on top of that, like a current parasite like some hidden accessory.

First, get a new battery. Do not put two batteries in parallel or use an LFP battery or anything crazy like that.

I recommend Walmart EverStart Maxx 140R. If you want to go AGM, ACDelco LN1 AGM might be good, too. Even though the AGM voltage is different, I don't think the car will care too much about it. Summit Racing seems to ship to Canada. Let us know how it works if you opt for an AGM.

Walmart now carries the Prius Prime battery—EverStart MAXX 140R | PriusChat

ACDelco 88866037 ACDelco Gold automotive AGM batteries | Summit Racing

As @Hammersmith said, you probably won't listen to this either, but I gave it one more try.

 

It's hard for anyone to be amicable, when they're already on their back foot. Stopping tossing insults and look for some resolution, lol.

 

It is absolutely useless, Mendel. As @Hammersmith said, he won't listen to anything from anyone—period. Yet, he keeps posting and posting and posting. Why does he bother to post if he preemptively ignores everyone else? He then wonders why some people call him a troll.

Just like his latest posts: “The factory battery has a sensor harness.” It doesn't, and at least two of us has clearly told him that it didn't. (The harness is part of the car, not part of the battery.) Yet, he will repeat this falsehood another ten times, just like he repeated his AGM falsehood dozens of times. He will eventually find out that he was wrong, but he will still show no remorse.

 

Boys boys boys!

I swear sometimes we lose sight that the point of a forum is to post your problems, hoping that somebody has run into similar issues or has expertise that would offer feedback, ultimately helping each other out! For most other things, there's FB for that...

To the original poster, or any potential poster really, if you're beyond asking and taking advice, then clearly you're SOL because Toyota won't help you, and you're smarter than everyone here.

 

Yes. We want a picture. Because what you're describing does not match what anyone else has seen in their gen5s, and it doesn't match the official Toyota publications on the gen5(which I included in my last post).

Either you're misinterpreting what you're seeing, or something has been added to your car that might be the cause of your parasitic drain.

 

TO ANYONE THAT COMES ACROSS THIS THREAD IN THE FUTURE

The gen5 Prius does NOT have any type of sensor in the 12V battery. I don't know what Paul is seeing on his(since he won't post a picture) but it's not a factory sensor harness. There are only three things that connect to the battery: 1. The negative terminal; 2. The positive terminal; 3. A tube that directs noxious gasses out of the car. That's it. Don't get confused by misinformation.

 

So what is that yellow crimp lug wire? That does not look factory.