No, I kid not.

Sounds like you know more about it than me, but I've read that under conditions of flat traction battery there is an inverter that will kick in and add charge to it from the 12V auxiliary system. Logically that must be the case, otherwise it would be completely impossible to jump start a TCH with a flat traction battery. But, they can be jump started.

Part of my good fortune may be the way I started the car after the long hibernation. There seem to be quite a number of operating modes. I chose to leave my foot off the brake so as not to actually start the car, then pressed the power button twice to bring the system fully online in whatever mode that is with no start. After a minute or so, after everything had stabilized, I put my foot on the brake pedal and pushed the power button again to actually put it in "Ready" mode. From there it took the usual ten seconds or so to do the initial ICE startup. All perfectly clean. My perhaps false assumption is that the system was able to provide enough charge from the aux 12V battery to the traction battery to enable start of the ICE. Any way you slice it, the energy came from the 12V aux system. There's no way the NiMH traction batteries held their charge for two months.

 

How do you know the traction battery was 'flat"? If it started, you had a sufficient charge to start the car. Sitting two months in 110 degree heat is possible if the battery was fully charged when you left it.

There is NO way that little 12V battery can charge a traction battery from a no start condition to a start condition in a few minutes... or at all for that matter. Take a look at the total amp hours available from the 12V and then calculate the total amp hours available from the traction battery.

 

It's certainly not something I want to pick an argument over. What I can say for sure is that after two months sitting idle in 110° heat with an 8½ year old original 12V battery, the car started like no problem at all.

NiMH batteries generally don't hold much charge that long. The 12V battery clearly did. I turned on power and the lights and climate control came on like new.

 

My understanding is that the HSD maintains the traction battery charge in between a relatively small range -- say 60-80% -- of its actual capacity. That's how they get so many charge/discharge cycles out of the pack. Thus, a flat indication on the monitor screen does not necessarily mean the pack has no charge left, and it may still have plenty of capacity to start the ICE even in this condition.

I have a friend who has regularly left her Prius parked in her garage for 3-4 months at a time and although she has occasionally needed to recharge the 12V battery upon her return, the now 8+ year old traction battery has never failed to start the ICE. This kind of service is probably not good for traction-battery longevity, but it does indicate that it is capable of surviving long periods of disuse.

 

Warren,

I would suggest that you go ahead and proactively change the 12V battery before it leaves you stranded somewhere. I replaced mine earlier this year (built in 2007) with a replacement Panasonic from Toyota. The old battery has been sitting in the garage for 5 months or so and still has 12.1 volts showing. They are very good batteries with a light load service but they can go out at the wrong time and are not a normally stocked item with most dealers.

 

Climate control - likely AC you referring to - is not operated off 12V battery. Should you doubt again, I can copy paste from technical manual. AC operates off traction battery.
You HAD charged traction battery. There is no need to discuss this, as that the only way you can start the car. As in - start the engine. 12V is nothing more than a fancy and very expensive 12V storage. Of course, as it backs up power to ECM, and ECM control everything else, dead 12 means no start simply because the "brains" are dead. You can find many posts on how to jump start dead 12v BUT that is working only for cars that have enough charge left on traction battery.

 

David, in message #171 it sounded like you were leaning toward Exide for replacing your 12V battery. What made you decide to go with OEM Panasonic from Toyota?

 

Dave, the more I thought about it, with the original battery lasting more than 7 years, it was worth the price to go ahead and buy a factory battery as I have rarely seen one fail. I normally replace the batteries in my cars every three years as a preventative measure and this one lasts more than twice that length of time without breaking a sweat.


Granted, the 12V battery on the Camry does not have any starting duties nor large amperage draw spikes so it should last longer. In this case, I felt the price was worth it.

 

Thanks David, that sounds reasonable to me. Our 2007 TCH with 155,000 miles still has the original, hasn't shown any signs of trouble. But Minnesota winter is approaching, and I feel like I've pushed my luck far enough. Did you have a Toyota dealer do the OEM replacement, our buy it from their parts dept, or find it elsewhere?

 

I cheated..... Went to the parts dept and put it in that night when I got home...

It only takes about 15 minutes to change it.