Gen 1 Turtle mode-warm weather

Was car parked in the sun? With windows closed? Did turtle disappear after you drove it awhile, with A/C on?

 

Advice I've read, and it makes sense to me, is to run A/C in hot weather (fairly often in FL, I suspect), as air intake for HV cooling fan is on rear shelf, and cooler cabin temp air will make the HV happier.

 

Are you running on the original/OEM replacement/rebuilt traction battery and what mileage?
Not sure at what point you measured the module voltages but here's what I've found…If there's a difference between module voltages greater than 0.3v (0.69 in your case) the car engages turtle mode which allows it to charge all modules over 100% i.e. perform a top balance. When it does this the traction battery fan will be at full speed because the modules will get not a little warm. This is (or was) considered quite normal behaviour for my model and probably why there's no code. However, if it has to do this on more than 3 occasions it'll likely throw up the red triangle because one (or more) modules is failing and cannot be brought back into line with the rest. That's when you will get a few codes. Depending on how serious the ECU deems it to be will determine whether or not the car will allow you to drive it any further…ask me how I know this
Regards, Jay

 

I have little confidence that the turtle light and top balancing are related.

I caught my gen 1 doing a top balancing cycle several times (those posts are around here somewhere). The turtle light was not involved any of those times.

I did see the turtle light one summer day when taking a steep twisty road at very low speed. It seemed to be a warning that the car was putting a temporary limit on battery current because of extreme battery temperature or very low charge. Pretty much as the owners' manual explains it.

 

@ChapmanF

Understandably, for simplicity, the owners manual does not go into all possible technical reasons why a turtle might get set. It describes the turtle to drivers mainly as a battery temperature/reduced power indicator because that’s a clear message for drivers to drive cautiously. It focuses on temperature extremes and “drive without hard acceleration.”

However, as you know, the hybrid control system monitors many signals: pack voltage, module voltages (for imbalance), pack temperature sensors, cooling/fan status, inverter status, HV isolation, and current limits. If any of those conditions imply the pack can’t safely meet demanded power, the ECU will reduce output — and in that situation the turtle must be set to provide a visible driver warning for safety. A severe module imbalance, even when pack temperature is registering normal, is a legitimate reason for the ECU to limit power.

It has been suggested that Toyota only mentions pack imbalance and decreased power in 'R' to protect themselves from disgruntled purchasers immediately discovering that it might do that in 'D' while driving on the freeway—especially since they could be fairly confident it wouldn't be likely to happen until the pack had done many tens of thousands of miles.