12 Volt Battery Low

On many cars, the USB port is data only; no charging.

 

I went to test drive a Prime at my local dealership and the 12v was dead. Who knows how many batteries were run down and slow charged to be then put back in their new vehicles.

 

There's no need to remove the 12 battery to recharge. Owner's Manual says there is, but if it was telling you how to pee, step one would be to remove yur pants.

Our 2010 was built in August 2009, and we bought it November 2010, with 10~15 kms on it. 12 volt battery was completely toast. They tried to mask it, had it running ("warming it up for you" they claimed...) when we showed up for the test drive. That fell apart when we went out again, had to start it up a second time for something. Made a new 12 volt battery a condition of sale.

 

I'm sure you meant "READY" mode. IG ON will kill that 12V in a hurry.

Probably all of them.

 

When I get a chance this weekend, I will measure the voltage on my battery. I have been using my car just fine since the incident.

 

Since the battery just needs to throw a switch and boot up the computer, it isn't have obvious when it starts getting weak as in a car in which the battery needs to turn over the engine.

 

Yeah measurement with an electronic load tester is good. It'll give the bare-bone volts and the as-measured Cold Cranking Amps, and typically some sort of verdict. Dealerships will have one, but likely charge you. Automotive retailers selling batteries typically have them and will often test for free. If you want your own there's a lot of prosumer options, around $50~100. I've used a Solar BA5 for a few years now.

 

Yeah, it works just fine until it doesn't work at all. Nothing comparable to the slow cranking of an ICE telling you that the battery is weak.

 

Get something like this:

Before you start your car press the Start Button with your foot off the brake. That puts you in IG ON mode. If the voltage is below, say, 11 volts the battery should probably be charged.

 

Ugh...

 

i had early warning signs on my 2004 and 2008

 

i had my low voltage experience a couple of days ago... car charged as usual in the early morning for departure, got the email saying that was completed... got in the car, pressed the brake, pressed power/start... got a warning 'low 12 volt battery' and the car did not move... then there was flashing lights on the dash... then it died totally...

had to have aaa come to my garage and jump it... called my local mechanic and the dealership... figured dead battery, and maybe it was under warranty... after the jump, it booted up, i drove it to the dealership, maybe 3 miles? they charged me $140 to check it out... found nothing... battery fine, there was a check engine light on after the jump, they said it was an old code with something about voltage...

they said i may have left a door open... the car usually tells me if i do that... but until this recurs i am guessing/assuming operator error... a lot going on monday night and i could have been distracted...

my question: what are the likely culprits for what i did that discharged the 12 volt? door open? left it on? fan? it was cold, in the mid 30s here at night lately... i did my usual routine, shut it down, walk around and plug in the charger, lock it up and go in the house... or so i thought...

 

Did the service writer give you a print out of the battery load test? He should have. If not, phone him and ask if their records of that service call contain the info. If it shows low, you need to buy a new battery. They're somewhat common and used in other small cars...Deka or NAPA 5140RMF, about $150. Not all battery makers nor marketers offer this size. (Johnson Controls and Exide are the other two main manufacturers. Interstate or Sears Diehard, for example, are marketers.) (Our 2017 Prime battery is still doing fine.)

Or, the car's system did not keep the battery charged. This would be a warranty repair. That diagnostic procedure should have looked into this. You should be able to get a specific answer about this from the service writer.

Or, you left a door open or somehow caused the battery to be drawn down. By the way, cold weather slows the chemical reaction inside the battery reducing it's capacity. You can easily use a simple $5 digital volt meter to check the battery's state of charge occasionally. Let us know what voltage you read.

 

I don't think anyone knows for sure what could cause the battery to drain. In theory everything should shut itself off after a while.

If you left it on in READY mode the HV battery charges the 12V battery, and the engine will run as needed. It beeps if it's on when you close the door. I don't know what happens if you plug in the charger while in Ready mode, if you accidentally left it on. Does it go to Accessory or "Ignition On" mode?

I think accessory and "ignition on" will automatically turn off after some time, but I don't remember how long. I don't know if the car beeps if you leave and close the door in one of these modes.

If you leave a door open or even an interior light on, I think there is a timer that should turn off the lights after some time. The indicator on the display showing that the door is open might or might not turn off.

If you leave the headlights on after parking, they will turn off after a delay (usually about 1 minute). But I've noticed that it is random or maybe buggy. Sometimes they seem to stay on longer than other times, and one time I saw them stay on for 5+ minutes for some reason, but maybe I left a door open?

Another possible problem, on my older Toyota if you leave the headlights on when you turn the car off, they will go off after about 1 minute. But if you turn the headlights on after turning the car off, the headlights will stay on for quite a while or maybe forever, and could drain the battery. I have not tested if that happens on the Prime.

 

Any modern car makes a steady, low-level demand on the battery, to maintain volatile memories, do self-tests, listen for fobs. Anywhere between 15 and 50 milliamperes, depending on the car.

Add to that a left on map light, door ajar, something similar, the battery will be below 12.0 volts in 12~18 hours.

 

That is true. But the 12V battery can supply the background drain for several days or ideally a couple weeks, especially in a car where the battery is not at the end of its expected life.

The point with my post was, almost everything that could drain the battery has a timer that will shut it off eventually, usually before the battery is drained. It's not like old cars where you could leave an interior light on all night. But there may be some rarely encountered scenarios that override that timer, either intentionally or as bugs.

Of course it's possible that leaving one of those things on only as long as the timer allows could drain the battery. Ideally it shouldn't happen.

 

Actually lead acid batteries have a design life of 3 years, unless you spent the extra money for the long life ones. Mine started dying about November of last year but the discharging started occurring more frequently until I dropped it off the night before its 2 year oil change this June. I knew the battery would die before they got to it the next morning, but sometimes that’s the only way they see a soft short and thus a bad cell. Anyway they put in a new one under warranty. Primes have a rather small battery and they get stressed more so I shut my lights off when I turn off the car and immediately turn them back to auto. Since I have an advanced model I have cellular running in the background as well as other drains (parking sensors, etc. ) that the DC-DC converter has to supply to the battery. I noticed through my OBD app my battery starts out getting 13.7 V but drops to only getting around 12.5 V while the car is on.


Unsupervised!

 

I'm not sure about that automatic shut-off function: I've left a door a ajar, and battery was around 11.9 volts when I discovered, 18 hours later. This is on a 2010, maybe getting into "old" category, though, lol.

 

I'm starting to think this was an even better idea now, compared to when I first implemented it.

Still going strong & working perfectly, all for ~$20 shipped.



Rob43

 

The car lets the voltage vary based on whether it needs to be charged or not. Maybe to save power. 12.5V is a little low, but not unusual. The DC-DC converter is plenty capable of supplying all the 12V load when the car is in READY mode, so I wouldn't worry about it. If the car kept the voltage at 13.7 all the time, some power would always be wasted in the battery because even though it's fully charged, it keeps absorbing some power. Instead it seems like it lets the battery float (as if it were not connected to anything), and the DC-DC converter supplies the load.

Batteries should last longer than 3 years, but it depends on the car and the climate and the size of the battery. I replaced the original battery in my 2007 4Runner just a year or two ago. They come with large Panasonic batteries from Japan, and they are known for unusually long life. I was sad to replace it, because no one sells a battery of equal quality in the United States. Even the USA market Toyota battery is just rebranded from one of the usual lead acid battery manufacturers.

Maybe leaving the door open is one of the things that still does not have an automatic shutoff. It could be worth testing it. Maybe when it's warm outside again I'll hook up my battery to my 12V charger and leave various things on to see what happens.