12v battery (hybrid) runs low after sitting for a week

[TacoFreak]

It's hard to believe that the dealers are telling people that it's normal and acceptable for your battery to go dead if you don't drive it for a week or two. That's crazy. My old 1972 Ford pickup would start after not using it for a month. How is this an advancement?

yeah - I completely agree. When my service writer told me that I needed to drive it more I told her that I could drive a couple of hundred miles and the charge would still be only 12.1 volts. Her reply was that I should get a trickle charger. Total BS and lack of support for a new truck IMO. This is the first vehicle I have ever owned that was not able to keep its 12 volt fully charged, and that is definitely not an advancement.

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[MustardTiger]

@nielsd beautiful pro! Great to see you got your battery issue figured out! Looks like we got our trucks from the same Toyota house lol. Since the truck I purchased had the battery replaced by the dealer (before it even went on the lot - assuming it froze due to low voltage during transport - they never mentioned replacing it), I haven’t had any issues. For the winter, I am logged into the app for remote start reasons…so I’ll have to keep an eye out for any low voltage signs. My truck doesn’t have an alternator, so I’m somewhat concerned about that…but so far I’ve had no issues with the truck. While I haven’t been back to that dealer, I would probably trust them if I had to take it in. There’s far far worse in our region!

On a different note, keep tabs on your engine oil level during these cold snaps, especially if you’re making short trips. Oil dilution seems to be a potential issue on the max.

 

[nielsd]

@nielsd beautiful pro! Great to see you got your battery issue figured out! Looks like we got our trucks from the same Toyota house lol. Since the truck I purchased had the battery replaced by the dealer (before it even went on the lot - assuming it froze due to low voltage during transport - they never mentioned replacing it), I haven’t had any issues. For the winter, I am logged into the app for remote start reasons…so I’ll have to keep an eye out for any low voltage signs. My truck doesn’t have an alternator, so I’m somewhat concerned about that…but so far I’ve had no issues with the truck. While I haven’t been back to that dealer, I would probably trust them if I had to take it in. There’s far far worse in our region!

On a different note, keep tabs on your engine oil level during these cold snaps, especially if you’re making short trips. Oil dilution seems to be a potential issue on the max.

Thanks for the heads up regarding the oil. I'll take a close look when I do my first oil change at 800 km.

My truck was on the charger when I picked it up new. So it probably froze too. It has an alternator and seems to charge well, at 14.5v, when running.

 

[franx]

I have been watching my battery level since I had my battery replaced several weeks ago under warranty since it just died on me even though I have been driving my truck at least once weekly. Only had the truck for about 10months and dead battery.

Took some pics of the meter in the dash, on start up its been center (mid point of battery image). Seems to be about 14v. Then after a few min I see it dropping slightly and its just barely touching the battery image (not sure voltage? could be 12v?). Pics attached to show exactly what I am seeing. Not sure if this normal and I believe it is after reading this thread?

Checking with others on the forum?

 

[MustardTiger]

@franx I would say after a few minutes of runtime it should not be dropping to that level on the gauge. It should only drop after extended run time and when there isn't much amp draw (no headlights on, minimal accessories, etc). If you have a battery health tester, try that and see what is says. You have to enter the CA's, and it will determine the state of health (%). They aren't that much money and are quite handy. Your battery could have a bad cell, and the sooner you know the easier it will be to get it swapped out under warranty.

 

[franx]

MustardTiger thanks for the feedback. I did have the headlights on, the heater on, radio and maps running. When I started it up again later same thing happened, it was centered then after couple min dropped to where it was before. The current battery is a replacement that was swapped out just a few weeks ago under warranty so not sure if its a bad battery again?

 

[GSPHerder]

2026 with an alternator. When i purchased it they had to jump it to get it out of the showroom. After some short drives when I put the volt meter on it it shows 12.7v. If I drive it daily it will hold the 12.7 but if it sits more than 2 days its now down to 12.3v. I signed out of the app but still occasionally received a notification on my phone even tho I was signed out. We need a way to stop the truck from all the telemetrics even when its sitting.

So much for a winch, I doubt this anemic 12v system could handle it.

 

[TacoFreak]

@GSPHerder 12.2 volts is where my battery settles, no matter how much I drive it. I don't think it is drawdown either, because it is that low right after driving it for hours. My maintainer will get it back up to a normal resting voltage but over a few days the truck lets it go back to just over 12 volts.

@franx I think what you are seeing is normal for these trucks. Mine jumps up to 14 volts right after I start it, but it quickly drops down and stays there. I think that is why they don't keep the 12 volt fully charged. My dealer just blew me off and didn't do anything, so I guess it is what it is. It keeps starting, but no way will the battery live very long being always undercharged.

 

[GSPHerder]

@GSPHerder 12.2 volts is where my battery settles, no matter how much I drive it. I don't think it is drawdown either, because it is that low right after driving it for hours. My maintainer will get it back up to a normal resting voltage but over a few days the truck lets it go back to just over 12 volts.

@franx I think what you are seeing is normal for these trucks. Mine jumps up to 14 volts right after I start it, but it quickly drops down and stays there. I think that is why they don't keep the 12 volt fully charged. My dealer just blew me off and didn't do anything, so I guess it is what it is. It keeps starting, but no way will the battery live very long being always undercharged.

I think it has to be a drawdown, if not then your suggesting the stock batteries have a memory of sorts that will only retain 12.2v. If that's the case then a good after market battery would retain more?

(just checked my wifes hybrid Grand Highlander, its sitting at 12.2v with a voltmeter)

 

[TacoFreak]

I think it has to be a drawdown, if not then your suggesting the stock batteries have a memory of sorts that will only retain 12.2v. If that's the case then a good after market battery would retain more?

(just checked my wifes hybrid Grand Highlander, its sitting at 12.2v with a voltmeter)

I am not an electrical engineer, so I could easily be wrong. But if my maintainer will charge it to 12.8 volts and my truck will only charge it to 12.2 I think it is the truck, not the battery. The strange part is that I can check it just after driving and then a day later and the voltage is the same. After sitting one hour, one day or one week it is always 12.2v checked with my multimeter.

I do know that you can't keep a 12v at such a low state of charge and expect a long life. I plan to get an Optima yellow top which can handle deep discharge but I don't expect it to be resting at any higher volts than the OEM battery. This seems to be common in Toyota hybrids and as long as the battery outlasts the warranty I don't think they care.

 

[GSPHerder]

I am not an electrical engineer, so I could easily be wrong. But if my maintainer will charge it to 12.8 volts and my truck will only charge it to 12.2 I think it is the truck, not the battery. The strange part is that I can check it just after driving and then a day later and the voltage is the same. After sitting one hour, one day or one week it is always 12.2v checked with my multimeter.

I do know that you can't keep a 12v at such a low state of charge and expect a long life. I plan to get an Optima yellow top which can handle deep discharge but I don't expect it to be resting at any higher volts than the OEM battery. This seems to be common in Toyota hybrids and as long as the battery outlasts the warranty I don't think they care.

So good point, when i took delivery the battery was dead/needed to be jumped. The vehicle/alternator charged it too 12.7v after a few short drives, and will maintain that as long as I drive it every day or two max. So my vehicle with the alternator is capable of charging it too 12.7 and not drawing from that as some have reported during a drive. Only after sitting a few days does it drop down.

Gonna start looking for a great aftermarket battery, starting with the yellow top. Id rather spend the money to find out than always wonder if my vehicle is gonna need a jump or not.

 

[StreeTaco]

A simple tweak to the next software update would remedy this issue. My battery drops to 11.3V resting voltage in a week. The system shows over 14v upon start up and then drops to 12.6~12.8.. this means the system pumps the accessory battery until it reaches what the engineers deemed full (12.6) and then goes into a float/maintenance mode. The float mode should actually be at 13.8v, not ~12.5v. Raising the float voltage threshold would keep the battery in a healthier SOC, and could easily be done thru the software.

 

[TacoFreak]

A simple tweak to the next software update would remedy this issue. My battery drops to 11.3V resting voltage in a week. The system shows over 14v upon start up and then drops to 12.6~12.8.. this means the system pumps the accessory battery until it reaches what the engineers deemed full (12.6) and then goes into a float/maintenance mode. The float mode should actually be at 13.8v, not ~12.5v. Raising the float voltage threshold would keep the battery in a healthier SOC, and could easily be done thru the software.

I agree. This should be no more complicated than some new software. But Toyota insists that this is totally normal, like they have changed the chemistry of 12 volt lead/acid batteries. As long as they won't admit that this is a problem they won't fix it.

I love my truck and plan to keep it, so I carry a jump pack in case the battery goes so low it won't turn on, and when the OEM battery dies I will get my Optima. I have used them before and they absolutely can handle the abuse that Toyota hybrids dish out. What I don't understand is why Toyota doesn't even try to address this and just has their dealers lie to us and blow smoke up our asses.

 

[MustardTiger]

Have you tried turning the switches off for all the lights, interior/cargo…leaving the rear drivers door open…letting the system power down and go to sleep….then testing the battery once things have had time to settle? Every time you open the door it awakens a bunch of modules and shit, then you naturally get a low voltage reading from the battery. Idk…I definitely have observed some, what I feel, is odd battery charging behavior, especially when the truck was new. But I kinda eventually landed on whatever, if it goes dead then I’ll deal with it then, and stopped worrying about it. Still hasn’t gone dead, and everything works. Truck can sit for a week and all is good. Idk!

 

[TacoFreak]

Have you tried turning the switches off for all the lights, interior/cargo…leaving the rear drivers door open…letting the system power down and go to sleep….then testing the battery once things have had time to settle?

Good question, and no I have not done that. You are right that a whole lot of stuff happens just by opening the driver's door. The closest that I have come was once when I checked it daily looking for a trend. I work from home and don't drive it daily and I left the hood unlatched to make it easier to check it at the jump point. The voltage was at 12.2v on the first day and it never went lower than that over five days.

One thing I did try was to compare my reading at that jump point with the voltage reading from my Carista. The voltage from the OBD2 port was a couple of tenths higher, so maybe the reading under the hood is not accurate?

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