Proper battery maintenance by some one who knows what he is doing and you will never have troubles, or extremely rarely. One cue we used on one particular type was when you initially hit the start button if the voltage didn't drop below 14 (28 volt system) you would have no trouble. Anything less, watch out. On one operation we were doing, flights only lasted 15 minutes (not good use for the cycle count and not a Caravan) and the last start of the day was always as good as the first. Again we had exceptional maintenance.