I've had one for a few years now and I love it all though if used improperly can get confused and select the wrong cell count. I've seen many threads on the 109 where people have had fires and all sorts of problems, All issues could have been avoided if the user reads the directions and keeps track of what the charger is doing. 99% of the time the problems come from a user trying to repeak a lipo pack which is not necessary but I do it myself if the pack has been sitting for two weeks or so. There are three phases that the charger will go through when charging "C1" will hit the battery with the amps you select and can change cell count depending on voltage, "C2" will apply the selected amps to the battery and won't change cell count(some of the early software did allow cell count to change but was adjusted in later software so it won't change) and will continue to apply the selected amps until the battery reaches the correct voltage, 4.2 volts per cell. "C3" will bump the battery with the selected amps until it reaches 4.2 per cell then amps will go to "0" and the voltage will fall below 4.2 and the charger will hit with amps again, it will go back and forth like this until the battery will hold 4.2 volts per cell and when it does the charge process will stop and the charge is done. There is a safe way to repeak lipo's if you feel the need, do this.
1. Plug in charger to power supply
2. Turn amp knob to 0
3. Connect battery and wait 3 minutes until the "C1" phase is done
4. Adjust amps when the charger is in the C2 phase
5. Keep an eye on the battery
6. Have fun without the risk of fires
Follow these simple steps and you will have no problems.......BB
.....It's not a problem until it's on fire....