Unexplained turtle sighting

The turtle light means that the traction battery is at abnormal temperature (either too cold or too hot) so it can't produce much power and you should drive "like a turtle", i.e., with light throttle applied.

It is unusual to see the turtle light if you haven't been driving up a mountain in high heat. But if you don't see it again, then no worries.

If you do see the light again and you are not driving in a stressful way, then you might be getting an early warning that your traction battery is about to die, which would not be too surprising since your car is 10+ years old.

 

I wonder if it might have been the mysterious "charge balancing" cycle I read about?

For peace of mind, there is a documented Toyota process to measure traction battery performance. It would not be cheap but it could give some confidence back.

Bob Wilson

 

I have experienced similiar symptoms in my Gen I. Like you said, turn the car off, let the battery cool down and the turtle goes away. I'm not sure what causes the system to do this but mine has done this twice since I've owned it (battery continually charges (even though its completely full), ICE never shuts down even at a stop and once the battery heats up, turtle light comes on). The second time this happened, I turned it off b4 the turtle light came on and it resumed normal operation after that. I think its some sort of glitch.

The last time mine did this was over a year ago and it hasn't happened since. Nor have I had any problems with the car since then.

 

Well, as you know, the big indicators are mpg and DTC's. Why not try driving it in battery mode for a while to see if you can get the SOC down. The best thing to do would be to monitor w/ a scanguage. Absent that, monitor it on the "Energy" screen, drive it in full electric mode (flat road, 20-40 mph) and see if you can get the batt indicator to drop to 50 or even 25%. This will tell you if your indications are working but I'm betting they are.

Let us know the results.

 

The dealer can manually put it in charge balancing mode with TIS. From what I think I understand, the ICE charges the battery above 90% and then you are supposed to discharge back to 70% slowly. It would be interesting if the ECU can do this on it's own, as force charging stops at 80%.

The idea is that the car is force charging all the modules until they just can't take anymore and thereby balancing the voltage/capacity reasonably well. I guess the analogy would be filling an ice cube tray, you might have some sections lower than others, but if you just fill the whole tray until the water is overflowing every section, they are all starting at about the same level.

If after this event you don't notice the battery fan is being loud, and you have decent EV range and you don't notice the SOC jumping around, it would imply your pack is still in good health.

 

This sounds normal on a balance battery as the ECU tries very hard to keep the SOC right at 60%. If you can find a stretch of flat road that is 35mph, you should be able to lightly press on the gas or alternate letting off the gas then pressing the pedal down a few cm and see if you can drive a few miles with the ICE off. You should notice if you can drive in EV only, you will at some point see the SOC bars drop.

(Note: your SOC isn't 75% unless you have a scanner, if you are looking at the display then say the SOC display is 3/4 which corresponds to 60% SOC. 2/4 is under 55%, and 4/4 is over 75% or something like that based on hysterisis). Basically without a scanner all you can say is green/blue/red. The Gen I keeps the SOC between 45% and 80% and tries very hard to keep it most of the time at 60% (except for EV mode, reverse, regen braking, hills, maybe passing on the freeway)