Weak 12v Battery = Cannot Complete Alignment

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This was a new one for me.

I took the 06 Prius that I had been working on to a local tire shop for an alignment. After the alignment was completed, it was necessary to perform a zero-point calibration, which is common for all Toyotas equipped with stability control. The Hunter Alignment Consoles are now able to handle this through their Codelink attachment, which is a unit that plugs into the vehicle's OBDII port.

So, the alignment tech plugged in the Codelink and allowed the software to check the systems and begin the calibration process. Almost immediately, we get a "low battery voltage" message and the process was unable to continue. We tried again and again, but received the same result-- the Hunter software simply would not allow us to proceed with a low battery voltage. I had already suspected 12v battery issues with this car due to low MPG (common sign) and slow/jerky engine starts, so this incident only confirmed that suspicion.

Luckily, this was a full-service shop so the mechanic in the next bay brought over his Snap-On Verus. The mechanic was not familiar with Toyotas, but once we entered the Wheel Alignment Menu the software gave us the option to perform a steering torque sensor calibration. At the time, we were not sure if that was the same thing as a zero-point calibration, but I later found out through my shop foreman contact that it was. The calibration was successful, and now the steering feel is much, much better.

The lesson learned from this incident was that with the advancement of vehicle electrical systems, the battery plays a critical role in proper functionality. Having all systems working properly is needed to complete repairs that used to be simple.
 
Never heard of that. Good to know. How was the service there? I am in need of alignment(one thing we don't do
frown.gif
. ) I am tempted to take it to the nissan dealer in fairfield, there having a four wheel alignment special 88 bucks. But I've seen how they run that shop and I do not like it.
 
Originally Posted By: finalyzd
Never heard of that. Good to know. How was the service there? I am in need of alignment(one thing we don't do
frown.gif
. ) I am tempted to take it to the nissan dealer in fairfield, there having a four wheel alignment special 88 bucks. But I've seen how they run that shop and I do not like it.


This took place at an independent tire and repair shop in the Santa Cruz area.
 
Originally Posted By: The Critic

The lesson learned from this incident was that with the advancement of vehicle electrical systems, the battery plays a critical role in proper functionality. Having all systems working properly is needed to complete repairs that used to be simple.


Agree. I was in Boston recently on business. It snowed on the way to my class, and everybody had headlamps on. A classmate pulled in next to me in his rental Kia and parked. He didn't realize until days end that he left the headlamps on. We had both pulled in nose first close to where they had piled up about 4 feet of snow from previous clearing of the lot. We could not push the Kia back away from the snow because pressing the brake to release the selector from park is an electric solenoid, not a mechanical connection. It was a pain to get him jump started.
 
I know on the RX400h, a low 12 volt battery can lead to all sorts of weirdness - message in dash display that vehicle must be in park to start when it's already in park for example.

Also on the 400h, a low voltage or a disconnected then reconnected 12 volt battery can cause the engine to idle more than necessary, engage more than necessary while driving, and lead to pronounced gear clatter from the transmission until a reset procedure is done.
 
GM dealers have, or should have, a 12V power supply they use to power the car when performing a PCM flash. It would be bad if the battery died in the middle of the flash...
 
Doesn't the traction battery invert power to charge the 12v battery?

I also thought the 12v was merely used only for backup and the Prius was started via the MG's? If they couldn't it relied on the 12v starter.

Seems odd a hardly used 12v would go bad like that, time for an AGM!
 
surprising that an 06 prius would be losing its accessory battery so soon-- it doesn't get cycled that much - not doing starter duty... does it provide lights/acc power during engine pause? Or does the traction battery use a down-converter to provide 12V power then too?

I think this thread is a really cool bit of info. On the Jeep forums, the ECU and BCM can get really wonky when the batt gets low, even when the alternator is spinning. I have personally repaired a GM product (ECU wouldn't send start power to starter solenoid) and a Chryco van (clumsy shifting) by adding supplemental grounds.

M
 
Very interesting. On a mid 90's car, I've seen a weak battery throw on the seatbelt and other warning lights, despite nothing being wrong other than a weak battery. If it happened on a car of that era, I can see a weak battery causing havoc on all sorts of things (I suspect it caused transmission hesitation on my van, as it did that prior to me replacing the battery a couple of years ago, but hasn't done it since the replacement).
 
In one of our company Silverados there were tons of bizarre symptoms that were all cured when we found out the factory battery connection was bad.

This truck did some really weird stuff, and it was all fixed with a new lead. So anything is possible...
 
Originally Posted By: meep
surprising that an 06 prius would be losing its accessory battery so soon-- it doesn't get cycled that much - not doing starter duty... does it provide lights/acc power during engine pause? Or does the traction battery use a down-converter to provide 12V power then too?

I think this thread is a really cool bit of info. On the Jeep forums, the ECU and BCM can get really wonky when the batt gets low, even when the alternator is spinning. I have personally repaired a GM product (ECU wouldn't send start power to starter solenoid) and a Chryco van (clumsy shifting) by adding supplemental grounds.

M


Heat and age will eventually cause any battery to wear out. 5 years is a realistic lifespan for most high quality lead acid batteries if they are kept fully charged (usage doesn't seem to be a big factor, but maintenance is). There are stories of lead acid batteries lasting much longer, but that is rare.

Now, it is possible that the 12Volt accessory might appear to last longer on a Prius since I understand it isn't used to start the gas engine (someone please correct me if I'm wrong). Since the load on the battery is low, the symptoms of failure won't necessarily show up. Usually, a dead battery will power the PCM, BCM, radio, etc in a regular car even when it is too weak to start the engine. In a Prius, this probably doesn't matter as much. Therefore, it may appear that the battery is good when it has in fact lost a substantial amount of capacity.

If the battery has a completely dead or shorted cell, then it will be completely useless in any car.
 
Originally Posted By: meep
surprising that an 06 prius would be losing its accessory battery so soon-- it doesn't get cycled that much - not doing starter duty... does it provide lights/acc power during engine pause? Or does the traction battery use a down-converter to provide 12V power then too?



If it's like the RX400h (and I think the basic systems are the same), the 12 volt (or auxilliary battery as Toyota calls it) powers everything that would normally be 12 volt powered on a regular car. Lights, radio, climate control, door locks, windows etc etc. This is whether the engine is running or not. It is charged from the traction battery, so there is no alternator.
 
Originally Posted By: meep
surprising that an 06 prius would be losing its accessory battery so soon-- it doesn't get cycled that much - not doing starter duty... does it provide lights/acc power during engine pause? Or does the traction battery use a down-converter to provide 12V power then too?


I think the 12v battery on a Prius is more prone to failure because it is very reliant on charging from the traction battery. If you make a lot of short trips, the 12v battery may not stay fully charged.
 
Originally Posted By: The Critic
Originally Posted By: meep
surprising that an 06 prius would be losing its accessory battery so soon-- it doesn't get cycled that much - not doing starter duty... does it provide lights/acc power during engine pause? Or does the traction battery use a down-converter to provide 12V power then too?


I think the 12v battery on a Prius is more prone to failure because it is very reliant on charging from the traction battery. If you make a lot of short trips, the 12v battery may not stay fully charged.


OK but technically it doesn't matter what the SOC the traction battery is at for the 12v to charge. It is drawing a constant current from it to charge itself, it's not like an alternator. Unless Toyota limits how much the 12v is charged via software.
 
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Originally Posted By: Thermo1223

OK but technically it doesn't matter what the SOC the traction battery is at for the 12v to charge. It is drawing a constant current from it to charge itself, it's not like an alternator. Unless Toyota limits how much the 12v is charged via software.

I will look on Priuschat and research this. I see it mentioned quite frequently that the 12v will not stay fully charged if the car is used primarily for short-trips.
 
Originally Posted By: The Critic

I will look on Priuschat and research this. I see it mentioned quite frequently that the 12v will not stay fully charged if the car is used primarily for short-trips.


Wow that seems a little silly but I'm sure there is a greater purpose that Toyota foresaw but I can't
lol.gif
 
no alternator- uses converter from trac batt - makes sense, fewer belted accessories to spin. gotta appreciate the thought that goes into this...

M
 
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