Battery Dying Way Too Soon

unfortunately, this is a fairly common problem with the prime 12v. some think it is a bad batch of batteries, others think it might be the charging system.
have a conversation with your dealer and see what they think. it should be under warranty.

sadly, most people have found there is a long back order situation.

 

its under warranty isnt it? go back to tue dealer

 

This happened to me once a few months ago.
I now monitor the 12v battery voltage with a meter I plug into the auxillary (cigar) port.
It's been fine.
I just got back from a one week vacation where the Prime sat in my garage and things were fine when I got back.
In hind site I think the first (and so far only) time I had the low battery issue I was driving
infrequent short trips due to winter.

PS. I did pick up one of those hand held Li-Ion 12v battery jumping devices just in case the problem
reoccurs when away from home. I added a 3 month reminder in my calendar to keep that device charged.
I may increase the interval if 3 months is too often.

PPS. I raised the issue with the Service Manager at my dealership and he said they see similar issues
from time to time on other Toyota models. Corollas especially. He suggested getting a battery maintainer
and topping off the battery weekly if the car is only driven infrequently and for short trips.
I already had the maintainer and so far have not used it on the Prime but if I need it I have it.

PPPS. I asked about @bisco 's theory on a batch of bad batteries. The Service guy said he had not
heard of this one.

Hope this helps.

 

for short infrequent driving, this can be a problem. (although it shouldn't have been since toyota moved the battery to the engine compartment from the hatch)
but i left my car for 10 weeks this winter and it started right up. the 7 year old 12v dropped .3 volts while we were gone.

regardless of what dealers or mechanics say, something is either wrong with the car or some batteries.

no idea what corolla's problem is, it should have a decent size battery, at least they used to. maybe this is an area toyota is cutting back on quality to save a few peso's.

 

The 12V battery is charged from the traction battery. If the car had been plugged in there should be no problem with the 12V battery. There should be no problem with the 12V battery after a week & a half in any case in any car.

Ask the dealer to show you the results of two tests:
(a) a load test on the 12V battery. This takes only a couple of minutes using a load test device the techs have. This will determine whether the battery is bad or not. If the load test shows that the battery is OK, then:
(b) an amperage test of the battery system with the car shut off and the pumps and fans shut off. The tech connects an ammeter in line with the negative battery cable and measures the current flow. It should be almost zero. Their tech manuals should give the allowable current. Or, the tech uses a suitably sensitive DC clamp-on ammeter around the negative cable to measure the current flow. If there is excessive current flow, that will draw down the battery. Some electronic component is defective and must be replaced. Warranty job.

 

When you plug the Prime into 120/240 to charge the traction battery, the charger for that battery also charges the 12V battery. Was your Prime plugged in during the period it was not in use?

 

FWIW appears to be a production issue based on above posts.
So dealership warranty is called for, ask the dealer if any TSB are issued for this issue.

Two cent comment, did you leave an interior light on or a key fob to close to the car so it keep arming/ disarming...or something under these thoughts?

Again based on above seems like a issue Toyota knows about.
Good luck.

 

A bad 12v battery is just that--and it's not just Toyota I've seen go down lately. My last vehicle went through two batteries before I changed brands and got a good one.

Don't sweat it too much after replacement.

 

Yes. I plug it in when I park in the garage and unplug when I drive it again. But, it does appear that you either have a phantom load or a bad 12V battery.

 

There appear to be a few issues here.
Do you ever plug in the traction battery?
If your 12v died, why? Do you have a short or did you leave an interior light on.
If you don't plug the traction battery to the wall it won't charge the 12volt battery and running the ice for 20 minutes didn't charge the 12volt battery, the ice charges the 12v with 2 amps, it would take an 8 hour drive to top up a dead 12v.
So, first, plug the traction battery in overnight, then drive the car like you stole it.
Then, check the interior for rodent signs, if the little suckers are present and chewing wires you found your problem, if hopefully there are no rodent signs and your prius starts and drives like it should great.
If the dealer checks your obd2 port with their reader any problems they find will be helpful, butmight not be free.

 

once the hybrid battery is charged, the system shuts off. leaving it plugged in doesn't do anything, and even if it was long enough that the hybrid battery self drained a bit, it won't turn itself on unless you unplug and plug in again.

 

I brought mine to the dealer after it died 4 times. They said the battery tested fine but told me they can’t replace it under warranty because it tested good. I’m pretty sure the cell phone connection on the advanced puts the extra drain on the battery. I charged it up separately with a battery charger and haven’t had issues yet. But just to make sure I’m removing the entune app from memory on my phone when not in use.




iPhone ?

 

So the dead battery is the symptom, not the problem. The problem needs to be found. Measuring the amperage draw from the battery with the car off is the first step.

My guess...I know of Mazdas and Subarus* with the same problem of drawing down the battery during shut-down periods. It is not widespread, but it happens too many times. My guess is that a component from the same supplier that all the Japanese car companies use has some defective individual pieces.

The other possibility is that the traction battery is not correctly charging the 12V battery. This can be determined by the tech at the dealership. Or, one can check that for themselves if they're handy with a voltmeter. Still, not a battery problem, it's a problem of the electronic circuit that does the charging.

If the car in question is still within the state's Lemon Law period, I'd read that state's law and if possible file the Lemon Law repurchase claim. That will at least get the manufacturer's rep involved in finding and fixing the cause of the problem.

*A friend drove her loaner Subaru Ascent from Seattle to Montana & B.C. for a previously booked ski trip. Her 2019 Ascent has this same dead battery condition. They have a new, no-additional-cost, replacement car waiting for her, and the dealership and Subaru of America are putting the details together to give her the replacement car. She didn't have to file the Lemon Law claim, but she was ready to do that.

 

Yes, those orange LEDs are well know for sucking gigawatts...

To OP, you need to measure amperage drain when the car is locked. If it's anything over few milliamps, some module remains active. Could be a door lock - check if any of front handles is abnormally warm. Also, nothing plugged into OBD port?

 

The orange LED likely draws 1/10 watt at most. I’ll hook up my Kill-O-Watt and see.

 

It's like 0.01kWh/day. I have kill-a-watt meter on my EVSE.