First I have to say that for some reason not all i-MiEVs behave the same way. For example, turtle light goes on in different i-MiEVs at different values of SoC. In mine, when SoC goes down to 9,5% SoC, turtle goes on. But I know other cars where the value of SoC is not 9,5% (a little higher or a little less). Another example, I showed before that AC goes on in a quick charge when a sensor goes to 31ºC. Surprisingly, after it was seen in many other cars, I found one that only do it at 40ºC.
So, some things that I say will not be extendable to other cars.
In mine, I think total voltage is never used to bring turtle to life. I see turtle in two different scenarios. When a cell goes to very low values (2,8V or 2,75V) and when SoC is 9,5% or lower (whatever total voltage and individual voltages are). I saw a few times, getting turtle and then saw it vanish, when I did a stronger acceleration at low SoC (but over 9,5%). I suppose 2,75V where detected in the weaker cell, car cuts power, and as voltage recovers, turtle went away. The same with SoC - if I get 9,5% SoC I get turtle, but if I can regenerate some energy going downhill just ahead, turtle disappears. It's a game that I some (few) times play with my family, when we are sure (and until today we where always confident, well, I´m confident and they are confident in me) we will arrive home, just bringing and disappearing turtle for some distance (going 10% to 9,5%, going 9,5% to 10%, going 10% to 9,5%,...)(obviously there is a good distance going downhill arriving home from east). One of this days I will make a video of this for my youtube channel.
For this I have the support of caniOn, with that information I know how much energy left in the battery (and I also know what I need to arrive, doing the same route so many times), so we, instead of going in panic, have some moments of fun.
Riding an i-Miev since 4/2011 in Portugal, 100.000 kms.