S Keith is correct about the battery. I would just replace it due to age alone.

Your reasoning on the quality of the Panasonic is not bad, and the price difference with the Optima is not that much, however, the Optima is not a poor fit that takes fanagling to get in. The Optima is an easy to install replacement. With that said, you certainly will not go wrong with the excellent and reliable Panasonic which may only cost you a few bucks more per year over it's life, and perhaps even less if it really does last longer. My bet is Toyota picked Panasonic primarily for two reasons. First, Toyota has a home source bias, and second, Panasonic was probably the low cost bid. If Toyota chose the Optima, then I would expect Toyota's dealer to customer price of the Optima would be nearly the same as what they charge for the Panasonic.

 

Are you as jaded as I am about 12V batteries here in AZ, Alan?

At the time Panasonic and Toyota were 50% partners in Primearth EV... the company that makes the traction battery... even more Panasonic bias...

 

My TCH OEM Panasonic 12V lasted six years. Of the many cars I've had in Phoenix with lead acid 12V, one needed new batteries about every 18 months, while most about every 3 years, and a few got 4-5 years. The couple of cars I had in Indiana never got more than 4 years per battery, but there it was the heavy stress of hard and long winter cranking of poorly starting engines that killed them, while here it is the heat stress directly on the battery. The AGM in a hybrid should never see high stress (it is a low current battery that always has light duty as far as car batteries go), and probably is not particularly heavily stressed by either cold or heat. However, it does see a relatively high base load when the car is off, so that a deep discharge type battery (i.e., and AGM) is needed, as a lead acid battery would quickly die from the continuous small load needed by the hybrid system.

 

Yeah. I'm sitting at about 2-3 years across the board for the 8 or so vehicles I've had in AZ.

AGM is still lead-acid, and they don't like heat, but their deep discharge characteristics and reduced self discharge help offset the damage.

At least it's a dry heat, amiright!?

 

My OEM Panasonic was dated of 2006 and is still running as back up battery for gate opener. Nuff said.

 

Reading through all the posts, it's not clear as to which aftermarket battery will fit in a 2007 TCH. I understand there will be necessary mods. I just need to know what is the most common battery to buy to replace the dead Panasonic in my 2007.

Which one should I get?

 

I bought the D34 Yellow Top Optima.

Problem is, there isn't 14v going to to the battery as the battery discharges. Any suggestions?

 

It's not always 14V. What are you seeing?

 

The voltage recovers to say 12.3v, but when the car is started, it drops.

There is no charge voltage. As the car runs, the voltage drops. It does it at the battery and at the auxiliary power plug inside the car.

If it runs for 10 minutes, the voltage drops below 11v. If I drive it, the car will die over time.

 

I should note, prior to the auxillary battery not recharging, the hybrid was replaced. Before it was replaced I called the dealer and asked if it was ok to drive it there to get diagnosed. They said ok. After informing me the hybrid battery needed replacing for $4200, I politely declined and had an aftermarket Dorman 3 yr/unlimited mileage installed.

It was after this the generator (as I've learned it's called, not an alternator) is not recharging the auxiliary 12v battery. It was dated July 2007 and when a load was placed on it, the voltage dropped immediately to 9v. I then purchased the Optima D24 Yellow Top and installed. I thought all was well until measuring the voltage; there is no charge voltage going to the battery.

There are no warning lights or codes. With the brand new auxiliary battery the car will run normally until it simply dies (voltage continues to drop), then all the warning lights turn on including the same 'Check Hybrid System' and 'Check VSC' prior to replacing the hybrid battery.

As there is a connector at the hybrid battery referred to as the "low voltage control cable", it makes me wonder if the installer forgot to reconnect it when installing the replacement hybrid battery.