I just did a little more research at TBM site and it pretty much agrees with Fromeco's info that NO FLY voltage is 7.0 Volts under a 1amp load, but goes into more detail. Here's what it says (I've bolded some of it):

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- When a 2-cell pack reads 6.8v under a 1 amp load on a new pack, it has no capacity left.

- When a 2-cell pack reads 6.9v under a 1 amp load on a new pack, there is about 25% of the capacity left.

- Each 15 minute flight on an average 35% airplane uses about 400 mah. This offers 12 flights on two 2-cell packs. When you test the batteries and they show 6.9v, you have enough battery life for a few more flights, but don't do it!!

Be safe. When either battery reads 6.9v (or higher), stop flying and recharge.

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Again, with a 1 amp load, I'm going to stop flying when I get down to 7.0V. I'll charge before each day's flying and should be set for the day. Of course, I'll check voltage under a 1 amp load between flights to make sure I don't get down to 7 volts.