Low 12-Volt Battery Apply Parking Brake Securely...

the confusion maybe 'plugged in' and 'charging'. as elektroingineur posted in #17, the 12v charges with the hybrid battery.
but as in the pip, once the hybrid battery finishes charging, the 12v no longer charges, no matter how long you leave the cable plugged in.
and as he also stated, we don't know the charging rate, but likely enough to counteract normal expected drain plus some.

 

I just found the link and I agree, that’s where I picked up that info


Finally, Video of Prime Battery Disassembly | PriusChat

 

eureka!

 

It makes sense to me, you would be trying to charge the battery with two battery chargers.

 

Love Eric, he's great! Very very informative.

Posted via the PriusChat mobile app.

 

got the same problem, I havent driving my prime for about a month or so and this came on. Charge the battery with battery tender for about 7-8 hours and it at 80% capacity...this is a brand new car, something is draining the battery. The interesting part is after charging it, noticed the car battery percentage is down from 99% to 66%...what gives? This doesnt seems to be normal.

 

Every car imposes a slight but constant drain on the 12 volt battery.

And that's definitely enough time for that drain to become significant.

 

there have been quite a few reports of defective gen 4 batteries.

i believe there is a way to turn off sks on your fob. a good way to reduce 12v drain when your letting the car sit idle for awhile.

now that you have drained the 12v, pay attention to it. it can sometimes cause long term health issues.

the loss of your 12v charge messed up the battery display. ignore it and keep an eye on it.

did you leave the hybrid battery full for a month?

 

more recent evidence concludes that prime DOES NOT charge the 12v while charging the hybrid battery, iirc.

 

Perhaps it just doesn’t charge it much. There’s definitely a charger for the auxiliary battery; see post #17.

 

thanks, there is a lot of confusion over this. why would toyota reduce the amount of charge from the pip, it works so well in mine, i can't believe it uses that much electricity.

sounds like a design error. iirc, some have measured their 12v before and during charging, with no change. could it be that a healthy battery gets no charge at all?

do you know if the charger is mentioned anywhere in the owners manual, like pip? that would be a very helpful referral.

 

I missed this thread when first came up. What an informative thread it is! This thread should be on sticky.

Although I have not had any problem with my PRIME's 12v battery yet, I am now well informed of a potential problem it may encounter in future. BTW, while I was at this topic, I thought about upgrading my ancient battery charger. The one I have is probably >30 years old (Schumacher SE-1010 10 Amp Manual Battery Charger). The last time I pulled off the shelf and used it about a year ago, it worked fine on HCH's dead 12v battery, but I'm hesitant to connect it to my PRIME if occasion requires it in future.

From reading this thread, I am thinking of buying CTEK MUS 4.3 charger. My question, what are the differences between those models? All are CTEK MUS 4.3 charger, but different model numbers at slightly different prices.

 

The one on the left is the basic charger. That's the one I have, and it seems to work well. The one in the middle has a test mode, but it sounds like it just measures the voltage during starting and when the engine is running, which is not very useful for a complex car like the Prime. The one on the right is the Polar model, which is designed to work at lower temperatures. Just get the cheapest one.

 

Thanks. I will get the basic one.

 

Yeah that "basic" one is my advanced one, also have a CTEK 3.3. Hook up steps:

1. Connect to battery. (Display will run through the lights repeatedly, for 5~6 seconds, then go dark)
2. Connect to wall outlet. Now you can push the mode button, and with each push it shows a different charge option, or combo of options.

I'm a "frequent charger", due a car that often sits idle for at least a day, so I've hooked up the quick connect, so I don't have to fuss with alligator clips. Fourth gen (and Prime) are at least a little easier, with the battery posts directly accessible in the engine bay.

Mine is charging right now, and as often as not that's the case. Once it's hooked up I just leave it on until the next time the car is used.

 

Do you mean you top-off the battery so often when your car sit in a garage just for a day? My idea of battery tending in the past is like this. It's winter, very cold, temp is sub-zero (F). I go out to the car in a morning to leave to work. I turn my key, but the engine will nor turn over. The headlight is dim or completely out. Darn, I have a dead battery! I connect my good old >30 years old Schumacher SE-1010 10 Amp Manual Battery Charger. Leave it. GO back inside, have another cup of coffee. Then, go back out 30min to 1 hour later. I crank the engine. Engine starts. Let it sit on idle for a while, and I am on my way to work being 1 hour late. Now, I never did this routine on my previous Gen3 Prius nor current PRIME, but have done on HCH once, and many times on our old Sienna and previous Civic. So, here is my question. Is there a benefit on battery tending the way you do, many years before those dead battery symptoms appear on a car, especially on Prius (PRIME included)?

 

I think so. There's an inexorable drain on the 12 volt battery in any modern car. Especially with a car that's often sitting idle, at least a day, sometimes multiple days, doubly so.

It helps that it's very convenient for me, with an attached garage, and the quick-connect. I gradually got into this regimen maybe 2 years back, and have had an Optima Yellow Top in for a bit over 3 years now, so I guess this can be my experiment.

Once the charger has completed it's charging cycle it's just "ticking over", monitoring the battery and giving it a little kick from time to time. I think. I don't think it's using much juice, but honestly haven't monitored, saying hooking up to a "kill a watt".