12 volt battery is important!-maybe an issue summary for error messages?

[McCloud_Rainbow]

Thought I would start a new thread since this keeps coming up for people. I think I have a decent summary after reading the manual and all the various threads about error messages and the car not starting and being towed.

12 volt battery charge and health is extremely important to make sure the car starts and works properly!

• the 12 volt battery runs all the gauges and computers and is used to start the LC
• the traction battery (hump in the rear) powers the drivetrain motor and not the cars electronics and gauges and starter
• there is no alternator. The 12 volt battery is charged by the traction battery, but ONLY after the car starts up.

Below I am attaching a few pages from the manual that I found helpful re. 12 volt battery health:

1. Page 112 - the electric boost gauge/“MAX” gauge - everyone, myself included, thinks that battery level is the traction battery. See page 112 of the manual…it is NOT…it is one of the 12 volt battery gauges. You can also see the 12 volt battery level on the Auxilliary gauges (see page 111). I can’t find anywhere in the manual that shows where one can view traction battery level. REMOVED THIS PAGE AND REFERENCE SINCE CONSENSUS IS THE MANUAL HAS A TYPO.
2. Page 228 - don’t play with settings when the hybrid system/engine isn’t on. Like me, we all spend lots of time trying to figure things out and adjust our settings. We do this sitting in the driveway. We think, “it’s a hybrid” so the engine doesn’t need to run. I would hazard to guess that 12 volt batteries may be running down when people play with their LC settings for too long while in ACC mode instead of doing it with the engine ON and there are many scenarios where this can happen. Wake up the next morning to start the car and it won’t start because the 12 volt battery is discharged. Make sure the car is ON if you want to view and adjust settings!
3. Pages 622-623 - posted in another thread already, but worth repeating here. These are the “jump” procedures to boost the 12 volt battery when discharged. Everyone should know this. I would bet that when people get those billions of scary error messages and the car won’t start, instead of getting towed to the dealer, they should try to boost the 12 volt battery first to see if a charged 12 volt battery gets things going again. My gut tells me a simple boost solves the issue and gets them back on the road again. Still check the 12 volt, but I would be willing to bet this will get you going again.

In any case, hopefully this helps void some of the issues folks have been reporting.

 

[polarityswitch]

Great summary that we can point to when the need arises.
I was one of those that though the battery gage was for the traction battery and not the 12V battery.
It is interesting to see the charge level of the 12V batter swing so offten between 2 and 6 bars, lol.

 

[Lenny33]

Good info - thanks!

 

[The Groove]

That spells out clearly that the SOC gauge is for the 12V battery… any chance this could be a typo or error in the manual? I only ask because it doesn’t make logical sense to me when the Boost Gauge for the hybrid motor is shown as part of the same compilation. It would seem more appropriate to be what most of us thought, that the SOC was for the hybrid battery. What would happen if the 12V battery was disconnected while the hybrid system was running? Curious what the SOC would show…

 

[TheBat]

Any guess as to what that "state of charge" gauge below the MAX gauge is measuring? It does not correspond to the volts displayed alongside the oil pressure gauge on my 1958.

Someone else suggested that the manual might be wrong and it is in fact a traction battery state of charge which it seems to behave like it is.

Edit: @The Groove beat me to it

 

[JustinHEMI]

I think there's a reasonable chance of a typo in the manual about that gauge.

 

[McCloud_Rainbow]

Found another thread where someone questioned the manual having a typo and that the manual says the SOC gauge is for the 12 volt, but believing that it is truly the NiMH gauge. Said they put the auxiliary gauge on the same screen as the SOC gauge and saw them tracking differently to verify this. I will try this next time I head out to see how it looks.

Regardless of what the SOC is showing…keeping that 12 volt healthy is the most important thing and we do know the auxiliary gauge definitely shows the 12 volt battery health.

 

[chancellor]

I have been watching that Max guage pretty closely on my LC, and I am pretty confident that it shows the charge level of the hybrid battery. Long slow braking down a hill, that bar fills up.
Drive low speed when the engine clicks off, watch the max bar fill up on acceleration and the battery level drop

 

[polarityswitch]

The battery iconography says it all. It is the traction battery. Has to be as others have concluded.

 

[Don]

The 12 volt battery is charged by the traction battery, but ONLY after the car starts up.

The 12V is charged by the high voltage electrical system, which is a combination of the generator and traction battery. The vehicle has a generator, not an alternator. The high voltage /hybrid system is only on when the vehicle is on. AUX is 12V only.

 

[Don]

I have been watching that Max guage pretty closely on my LC, and I am pretty confident that it shows the charge level of the hybrid battery. Long slow braking down a hill, that bar fills up.
Drive low speed when the engine clicks off, watch the max bar fill up on acceleration and the battery level drop

Yes, no vehicle tracks the capacity of a starting battery. The LC tracks the volatge of the starting battery, as is shown on the actual 12V gauge. The OP's confidence that the battery fuel gauge is the 12V is lack of understanding of different battery types.

Like all vehicle the LC tracks the voltage of the starting battery. By contrast it must track the watt hour capacity of the hybrid battery for both regen and electric propulsion to function.

 

[Captain Trips]

I just disabled the ACC option. That way either everything is off or everything is on. There is no accessory mode. This way when you push the button once the hybrid system is on. The ICE will only start if your foot is on the break.

 

[chancellor]

Weird, I tried to cross reference the 2024 Tacoma hybrid owners manual to see if they had it correct there for what it has for that max gauge, it calls it the "MG Gauge" and the entire description is just "displays the motor power"

 

[McCloud_Rainbow]

I just disabled the ACC option. That way either everything is off or everything is on. There is no accessory mode. This way when you push the button once the hybrid system is on. The ICE will only start if your foot is on the break.

Didn’t know that was an option. Great idea considering how it works. Did you have to use Carista for this or is it in the manual?

I’d be Grateful for the counsel.

 

[MJE]

Learned something new today. Here I didn’t think you’d have to jump start a hybrid car as it has a giant reserve battery which is what I thought started the engine. Guess that’s totally separate from the starting circuit then.

 

[Nick]

Thought I would start a new thread since this keeps coming up for people. I think I have a decent summary after reading the manual and all the various threads about error messages and the car not starting and being towed.

12 volt battery charge and health is extremely important to make sure the car starts and works properly!

• the 12 volt battery runs all the gauges and computers and is used to start the LC
• the traction battery (hump in the rear) powers the drivetrain motor and not the cars electronics and gauges and starter
• there is no alternator. The 12 volt battery is charged by the traction battery, but ONLY after the car starts up.

Below I am attaching a few pages from the manual that I found helpful re. 12 volt battery health:

1. Page 112 - the electric boost gauge/“MAX” gauge - everyone, myself included, thinks that battery level is the traction battery. See page 112 of the manual…it is NOT…it is one of the 12 volt battery gauges. You can also see the 12 volt battery level on the Auxilliary gauges (see page 111). I can’t find anywhere in the manual that shows where one can view traction battery level. REMOVED THIS PAGE AND REFERENCE SINCE CONSENSUS IS THE MANUAL HAS A TYPO.
2. Page 228 - don’t play with settings when the hybrid system/engine isn’t on. Like me, we all spend lots of time trying to figure things out and adjust our settings. We do this sitting in the driveway. We think, “it’s a hybrid” so the engine doesn’t need to run. I would hazard to guess that 12 volt batteries may be running down when people play with their LC settings for too long while in ACC mode instead of doing it with the engine ON and there are many scenarios where this can happen. Wake up the next morning to start the car and it won’t start because the 12 volt battery is discharged. Make sure the car is ON if you want to view and adjust settings!
3. Pages 622-623 - posted in another thread already, but worth repeating here. These are the “jump” procedures to boost the 12 volt battery when discharged. Everyone should know this. I would bet that when people get those billions of scary error messages and the car won’t start, instead of getting towed to the dealer, they should try to boost the 12 volt battery first to see if a charged 12 volt battery gets things going again. My gut tells me a simple boost solves the issue and gets them back on the road again. Still check the 12 volt, but I would be willing to bet this will get you going again.

In any case, hopefully this helps void some of the issues folks have been reporting.


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Thank you so much for that. I hope I never have to use it.
So I went out to investigate it and to make sure my Noco jump starter cables would reach both the battery and ground bar and it looks like it will but I cannot for the life of me figure out how to get that cover off the battery. Would you mind showing me how? I searched and looked at online owners manuals and I can't find it. I'm sure it's just me having a brain fart. I do know if I had not read your post I would have never guessed where the battery is because you can't see it.