Hybrid Battery Life & Storage Conditions

I'm accustomed to getting far more than 200k mi on my Toyotas, so "the life of the car" for battery life, as according to a Toyota salesman, does not give me much comfort as far as battery life is concerned. No new-car salesman thinks a car is still young at 100,000 miles. They retire such cars into the car auctions. "Dead as a doornail" is maybe 150,000 for such people.

My 2002 prius has 125 kmi. I've been measuring battery capacity from time to time by backing it up a hiill and measuring with an altimeter how much altitude gain I get before the turtle blinks and the car goes limp. That's because, in reverse, it only uses the battery. I got about 280 ft at 32k mi, 325 ft at 60k, 425 ft at 90k, and it's back to about 300 ft at 120k. That'll give you a rough idea, but it's highly dependent on temperature, back-up speed and even tailwind.

So I bought a spare hybrid battery in 2003 (real cheap in those days before there was any demand for them) from a junk yard, with 26 kmi on it. It still sits in my garage waiting for enough information to determine how best to store it: fully charged, fully discharged or half-way. It's nigh impossiible to find anyone in the entire Toyota organization willing to discuss such practical matters or to share technical data such as diagrams of the battery pack's innards (not the chassis diagrams, the battery pack diagram). I can't get past the pretty voice on the Toyota P/R line.

Anyone who has that kind of data and willing to share it, please let me know: [email protected]. I have all the electronics needed to charge the thing, but I need to know where the terminals are to energize the internal relay. I'm not worried about the cooling fan because I can charge it so slowly it can't overheat. I also need to know about voltage balancing control for this series-parallel combination.

THEN I need to know if I even SHOULD charge it before it comes time to replace my original battery.

A "normal" camera NIMH battery pack is usually left charged on the shelf so as always to be ready to install. That's not the same as the longest battery storage shelf life. No one seems to know how to deal with that. How, for instance, does Toyota store their spare hybrid batteries? No one is willing to say. If only mileage counts, then I'm ok here with a 26kmi battery.

The Hybrid system is a Solomon Engine, which means it should be able to run even without the battery, by swapping power between the two electric motors and the engine. When I get the turtle, the car gets very cranky about accelerating from a stop for a few miles, but it goes ok. It's like a conventional automatic transmission with grabbing bands or a manual tramsmision with a grabby clutch. At that point, I take it a little easy with the jackrabbit starts...

Now, if the battery is really kept betwen 65% and 45% by the turtle mode, then why do I get these jerky starts when the battery still has 45% in it? Hm?

On the other hand, 300 ft altitude is a lot of energy for a 3500 pound car, and it's clear that very little of the 2002 battery is actually used. If the "life of the battery" means "the time it takes for the car to quit altogether", not merely "when it gets jerky", then I can believe about 200k. After all, in principle it only needs enough capacity to start the engine - maybe 5% of what's in there when it's new.

I think it's truly a great car, but Toyota may lose its audience if it doesn't come forward with more hard technical data on what to expect well beyond 150,000 miles. I have a lot of friends who are waiting for the "other shoe to drop" in my garage before they fork out the bread for a Toyota hybrid. The fact that the new models have half the battery energy capacity is no comfort to anyone. If half the capacity means half the effective life, it means the resale value on those new models drops to zero at about 90,000 miles.

Best,

phil

[email protected]