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

[Tom Sellick]

I have an OBD Link dongle that I can use to monitor various parameters. When I am in P, R, or N, I will see the voltage indicator above reading at the halfway point (5 segments) and voltage at the OBD port is 13.7 to 14.1. Once I select D, the voltage indicator shows the same as above (3 segments) and the reading at the OBD port is 12.7-12.9.

Yeah this sounds like what I see. I can’t measure it like you do but from watching the gauge…

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[TacoFreak]

Here are the results of my little experiment.

After charging for several hours my battery reached a peak voltage of 13.32 vdc. The maintainer was still charging but it never went any higher than that and I removed the maintainer. After sitting overnight it now reads 12.9 vdc and I will see what it does when I drive it.

I am not a battery expert, so I wonder what you guys think. Is that a normal voltage drop after 12 hours with nothing on in the truck? I didn't even open a door, which causes all kinds of things to run. Does that mean the battery might have failed or is the truck drawing the battery down? I do know that the truck has never charged it past 12.22 vdc recently and before that I never bothered to check it. Hey, it is a Toyota, why worry? lol

I will try to get it to the dealer next week and see what they have to say. Stay tuned.

 

[gpburdell]

I guess my thoughts on the alternator and 4th aux switch…this tells me the tipping point of needing an alternator is already very close on the trucks without the 4th aux switch…

Which would seems weird since the three AUX circuits are fused for 30A total per the owners manual (15/10/5). That's only 360W. Contrast to the 2400W inverter already equipped.

I have an OBD Link dongle that I can use to monitor various parameters. When I am in P, R, or N, I will see the voltage indicator above reading at the halfway point (5 segments) and voltage at the OBD port is 13.7 to 14.1. Once I select D, the voltage indicator shows the same as above (3 segments) and the reading at the OBD port is 12.7-12.9.

Now that is puzzling...

Here are the results of my little experiment.

After charging for several hours my battery reached a peak voltage of 13.32 vdc. The maintainer was still charging but it never went any higher than that and I removed the maintainer. After sitting overnight it now reads 12.9 vdc and I will see what it does when I drive it.

I am not a battery expert, so I wonder what you guys think. Is that a normal voltage drop after 12 hours with nothing on in the truck? I didn't even open a door, which causes all kinds of things to run. Does that mean the battery might have failed or is the truck drawing the battery down? I do know that the truck has never charged it past 12.22 vdc recently and before that I never bothered to check it. Hey, it is a Toyota, why worry? lol

I will try to get it to the dealer next week and see what they have to say. Stay tuned.

12.85V is a normal "resting" voltage for a fully charged AGM battery.

See the State of Charge table here.

 

[Tom Sellick]

Here are the results of my little experiment.

After charging for several hours my battery reached a peak voltage of 13.32 vdc. The maintainer was still charging but it never went any higher than that and I removed the maintainer. After sitting overnight it now reads 12.9 vdc and I will see what it does when I drive it.

I am not a battery expert, so I wonder what you guys think. Is that a normal voltage drop after 12 hours with nothing on in the truck? I didn't even open a door, which causes all kinds of things to run. Does that mean the battery might have failed or is the truck drawing the battery down? I do know that the truck has never charged it past 12.22 vdc recently and before that I never bothered to check it. Hey, it is a Toyota, why worry? lol

I will try to get it to the dealer next week and see what they have to say. Stay tuned.

Interesting. When I spoke to the dealer they said it's all the stuff going on in the background of new cars that causes this.....like you said sounds like an excuse but may be true. If true, that's crazy. Left my 2013 4Runner with 400000km on it in the Montreal airport parking lot in Jan-Feb for six weeks. Got in the truck and started right up! If I can't rely on this brand new, top of the line Toyota truck to start in the summer after sitting in a garage for two weeks....well.....

 

[TacoFreak]

12.85V is a normal "resting" voltage for a fully charged AGM battery.

See the State of Charge table here.

OK, that is interesting and thanks for the info. So I guess the battery is now fully charged, and it will be interesting to see what happens when I drive it. That chart will be a big help in letting understand what the voltage readings mean.

 

[TacoFreak]

Interesting. When I spoke to the dealer they said it's all the stuff going on in the background of new cars that causes this.....like you said sounds like an excuse but may be true. If true, that's crazy.

I understand that there is a lot more going on in today's vehicles when they are off than there was in the past. But Toyota's mission was to design an electrical system that can handle that, which they seem to have failed at.

From my POV it can't be normal for a parked truck to die as quickly as your truck does. If I was in your situation I would definitely elevate this to Toyota corporate. At the very least I would want a public statement that these trucks can't handle being parked for very long and that they consider that normal. That would certainly impact my decision on how long to keep my truck and what I would buy next. To me it seems like Toyota screwed up, just like they did with my transmission which is covered by the debris TSB, and they don't want the bad publicity of admitting it.

My battery never reaches full charge but somehow it still starts right up every time. It has never been parked for more than a week, but working at home and with two vehicles it frequently is parked for a week. I have a great dealer, so it will interesting to hear what they have to say about this. Good luck with your truck and contact Toyota Brand Engagement and see if they actually care enough to help you out.

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