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 understanding 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.

 

[EVOTACO]

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

Following up on my previous post observations. Did some more driving around with the OBD dongle active. It appears the 12v charging system kicks in as needed. I noticed it seems to check/charge after starting up the Tacoma and will run for a short period, again reading about half on the voltage bar or 14.1v at the OBD port.

Truck turned on (after stopping at a store)..

While driving after restarting...

Then will stop charging until the trigger parameter is activated again or the truck is shut off and started back up. The voltage at the OBD port stayed at 12.9v during steady state cruise. This is also with AC and audio running.

 

[Tom Sellick]

Following up on my previous post observations. Did some more driving around with the OBD dongle active. It appears the 12v charging system kicks in as needed. I noticed it seems to check/charge after starting up the Tacoma and will run for a short period, again reading about half on the voltage bar or 14.1v at the OBD port.

Truck turned on (after stopping at a store)..

While driving after restarting...

Then will stop charging until the trigger parameter is activated again or the truck is shut off and started back up. The voltage at the OBD port stayed at 12.9v during steady state cruise. This is also with AC and audio running.

Thanks for that! Good info!

 

[MustardTiger]

@EVOTACO thank you for sharing !! My question is when the charging isn’t active, and it says 12.9v on the OBD…where is the dash gauge at?

wonder if I can do this with my Carista thing

 

[TacoFreak]

Following up on my previous post observations. Did some more driving around with the OBD dongle active. It appears the 12v charging system kicks in as needed.... The voltage at the OBD port stayed at 12.9v during steady state cruise. This is also with AC and audio running.

My truck does not behave that way, but maybe I just have a bad battery. The lowest I have seen it is 11.9 vdc or about 35% charged.

A couple of days ago it was down to 12.18 after driving for 90 minutes. I put my maintainer on it and it charged up to 13 vdc while charging or 100%. Without the charger it was 12.85, also 100%.

Sitting for 12 hours that dropped to 12.57 vdc - about 80%. Strangely the next morning it was up to 12.67 - maybe 85%. So I took it for a drive to see what happend.

After driving for 25 miles of mostly freeway it is now at 12.42 vdc or about 75%. So using the truck actually reduced the charge level. When it is first started it is higher than after just a few minutes of driving, falling from the middle of the gauge to just even with left of that little battery symbol. The instrument cluster gauge jumps around a lot between what looks like 70%-100% charge, but maybe that is normal.

So next I will drive it for a few days and see it it settles back into a constant state of less than 40% charge. If my maintainer can get it to 100% I don't understand why the truck's charging system can't, but again very little about this system makes much sense to me.

 

[EVOTACO]

@EVOTACO thank you for sharing !! My question is when the charging isn’t active, and it says 12.9v on the OBD…where is the dash gauge at?

wonder if I can do this with my Carista thing

The dash gauge is displaying the lower 3 segments at 12.9v, like what was shown previously. Visually there are no segment lines, but the gauge will move in segmented increments. They appear to be displayed in 1v increments (i.e. 12.0-12.9, 13.0-13.9 for each segment).

Not sure of the functionality of the Carista brand OBD adaptor. I am using the OBDLink branded adaptor, which also happens to work with the Carista app.
https://www.obdlink.com/products/obdlink-mxp/

 

[MustardTiger]

@EVOTACO excellent! Well that settles it, I’m officially gonna not worry about this anymore!

 

[goin2drt]

My truck does quite a bit of sitting in the garage, as I'm away for longer periods of time. I've been monitoring the state of the 12v battery...and after returning a week later, I unlock truck and open hood...let things settle for 15 mins...and battery shows 12.0v. I feel it should be at least 12.5-12.6 (like 80-85% charge). Before driving it, I connect a 7.5 amp NOCO charger and let it complete a charge cycle. The truck has never not started for me however.

A couple things to note:

-my truck was delivered in the dead cold of winter, it was like -30c temps. The day I went to purchase, it was out on the lot, -35c...they just started it...immediately backed up through a snow bank and into the shop.
-it had been sitting on the dealer lot for about 1 month (in said cold temps) before I seen it and purchased
-after getting it home, I noticed the little red flip cover on the boosting terminal was broken at the hinge...and it was obvious booster cables had been attached at some point, maybe during transport? hard to say

Maybe...my battery was in a very low state of charge for an extended period, in freezing temps, prior to me buying it, and it either froze or lost a significant amount of life/amps

Anyone else have a 12v issue like this? Particularly the drain after sitting for more than 5 days?

Non hybrid TRD Sport and left mine for 2 weeks for vacation.

Came home and tried to start it and it just clicked and wouldn't start. Tried it again it clicked again and then started. Drove it around a bunch but randomly in the morning after sitting it does the same struggle to start. Dealer today. They checked the battery and said it was fine just needed a charge. Said they needed it for 3+ hours to do that so I left. We shall see how it goes.

 

[MustardTiger]

@goin2drt hmmm interesting. Do you keep signed in to the Toyota app all the time?

 

[Jt2024]

@goin2drt hmmm interesting. Do you keep signed in to the Toyota app all the time?

Not after the battery drained. No issues since I signed out after using it. Not sure but it may ping the vehicle.

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