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

[Cordoc]

Adding an alternator won't have any benefit unless you're drawing more power than the hybrid motor/generator can supply.

Also given other threads it's not clear that all 2025's are getting the alternator.



12.2VDC after a 30 minute drive is a bad battery (or bad charging system) regardless of AGM or lead-acid. Given the amount of self-discharge in two days it's likely the battery unless there's some significant parasitic draw.

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[Cordoc]

I have a 24 Trailhunter with no alternator, I have never had a battery problem.
In Jan I left the country for 2 1/4 months and went to the garage, and it started in 1 sec flat.
Any problem with starting after a few weeks should be investigated since it is not supposed to happen

 

[SnowmanJPS]

This is also the battery that is in my '24 OR hybrid. I carpool every other week and travel, so my truck sits for a few days and intermittently a week or so. Knocking on wood, I have yet to see an issue.

Same battery as my 25 pro

 

[max911]

Just a follow up to my truck getting a new (12v) battery from the Toyota dealership.

Was away for about ten days on a roadtrip in my convertible.
Returned home and the truck fired up perfectly when i tried it this morning.
Voltmeter stays at midpoint (14v) Whereas before it would drop down to 12v after 5 or 10 minutes of driving with the original battery.

I'm thinking there is probably enough of a sample size by now that Toyota must be aware that there was a bad batch of batteries that are failing in the first months/year.

 

[MustardTiger]

So I had the truck sitting for a good 10 days…I left a 1.5 amp maintainer on a WiFi switch, and had run it on two occasions for about 8 hours. Then left it off for five days…the voltage of the battery when I got back was 12.4v. So I then decided to put a 7.2amp Noco charger on it, and set it to the agm setting, left it overnight. The next day the battery had got up to 12.9v…so that’s good. I drove the truck and the voltage gauge will always remain mid way for a good amount of time (I’m assuming midway is between 14-15v). However it will still drop low after a while, like the system stops charging the battery completely. See picture.

idk…I don’t think anything is wrong with the truck or battery…but it’s the most bizarre voltage readings and behaviour. I’m going to stop worrying about it, maybe keep a small jump pack with me, and just drive it lol. As you can see I need to do that more

 

[Tom Sellick]

So I had the truck sitting for a good 10 days…I left a 1.5 amp maintainer on a WiFi switch, and had run it on two occasions for about 8 hours. Then left it off for five days…the voltage of the battery when I got back was 12.4v. So I then decided to put a 7.2amp Noco charger on it, and set it to the agm setting, left it overnight. The next day the battery had got up to 12.9v…so that’s good. I drove the truck and the voltage gauge will always remain mid way for a good amount of time (I’m assuming midway is between 14-15v). However it will still drop low after a while, like the system stops charging the battery completely. See picture.

idk…I don’t think anything is wrong with the truck or battery…but it’s the most bizarre voltage readings and behaviour. I’m going to stop worrying about it, maybe keep a small jump pack with me, and just drive it lol. As you can see I need to do that more

Mine is the same as yours. Recently did a road trip and watched the gauge over about 1000km. The vast majority of the time the gauge read roughly same as in your pic. There was a short period where it jumped to about half way. No idea what made the difference. Also have a jump pack and am going to get a trickle charger installed.

 

[TacoFreak]

That is how the charge level runs on my truck too. I don't plan to start using a charger, because if I need that on a new truck there is something wrong and Toyota needs to fix it. The first time it won't start I will get it to the dealer and expect them to do something. I do need to buy a jump pack though so that I can count on my truck, and I need to go over the process for unlocking the door when the battery is dead. It was kind of a PITA on my wife's suv and we had to check the manual to figure it out.

 

[Tom Sellick]

That is how the charge level runs on my truck too. I don't plan to start using a charger, because if I need that on a new truck there is something wrong and Toyota needs to fix it. The first time it won't start I will get it to the dealer and expect them to do something. I do need to buy a jump pack though so that I can count on my truck, and I need to go over the process for unlocking the door when the battery is dead. It was kind of a PITA on my wife's suv and we had to check the manual to figure it out.

You can just use the key that’s in the fob.

 

[TacoFreak]

You can just use the key that’s in the fob.

Cool.

On my wife's Lexus you had to remove part of the door handle because there is no external key hole. It was not obvious exactly where the removable piece was, which I guess is the price you pay for a sleek design.

 

[max911]

"I drove the truck and the voltage gauge will always remain mid way for a good amount of time (I’m assuming midway is between 14-15v). However it will still drop low after a while, like the system stops charging the battery completely."

TacoFreak- that is exactly what my truck was doing. The dealership said the battery was faulty and wouldn't take a charge. They installed a new battery and so far, so good.

 

[TacoFreak]

TacoFreak- that is exactly what my truck was doing. The dealership said the battery was faulty and wouldn't take a charge. They installed a new battery and so far, so good.

Thanks, that is good to know. I will need to get my truck to my dealer and have them test the battery as soon as possible. I have been way busy lately and haven't taken the time to go to the dealer, but it sounds like I should make that a priority.

Mine reads under 12v after it sits for a few days and the highest I have seen on my meter is 12.2 a few hours after a fairly long drive. I hope it is the battery and not something that is stopping my truck from charging properly. I will post when I learn anything new.

 

[Tom Sellick]

Thanks, that is good to know. I will need to get my truck to my dealer and have them test the battery as soon as possible. I have been way busy lately and haven't taken the time to go to the dealer, but it sounds like I should make that a priority.

Mine reads under 12v after it sits for a few days and the highest I have seen on my meter is 12.2 a few hours after a fairly long drive. I hope it is the battery and not something that is stopping my truck from charging properly. I will post when I learn anything new.

I took mine to the dealer when my battery died. The dealer charged and tested the battery. It passed the test and so they said there was nothing they could do. Toyota will only cover battery if it fails/gives a code

 

[TacoFreak]

I took mine to the dealer when my battery died. The dealer charged and tested the battery. It passed the test and so they said there was nothing they could do. Toyota will only cover battery if it fails/gives a code

Yep - it needs to fail a load test when it is fully charged. I'm not sure that my battery can be fully charged but I should test that by putting it on my maintainer on it for a while. If that gets it to an acceptable charge level and the truck does not keep it there, the problem is most likely the truck.

I don't understand your truck at all. If the battery is fine then why does it run down so quickly? If that is my situation I will elevate it to Toyota corporate attention and see what they have to say. In warm weather with a healthy battery it should be able to go weeks without being started. At least that has been true for all of the many vehicles I have owned.

 

[Tom Sellick]

Yep - it needs to fail a load test when it is fully charged. I'm not sure that my battery can be fully charged but I should test that by putting it on my maintainer on it for a while. If that gets it to an acceptable charge level and the truck does not keep it there, the problem is most likely the truck.

I don't understand your truck at all. If the battery is fine then why does it run down so quickly? If that is my situation I will elevate it to Toyota corporate attention and see what they have to say. In warm weather with a healthy battery it should be able to go weeks without being started. At least that has been true for all of the many vehicles I have owned.

I totally agree with you. It’s not acceptable. They just kept telling me that they deal with it all the time with new cars….and they install loads of trickle chargers for people as a result. They said Toyota is aware and supposedly working on it. I’m guessing that means for future models.

 

[TacoFreak]

I totally agree with you. It’s not acceptable. They just kept telling me that they deal with it all the time with new cars….and they install loads of trickle chargers for people as a result. They said Toyota is aware and supposedly working on it. I’m guessing that means for future models.

Yes - not at all acceptable. Lots of dealers suck, and yours seems to suck more than average. I don't think my dealer would jerk me around with that bs, but I guess I will find out.

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