Never caused a problem with me. I wish theyd add cc/cv endpoint adjustment, I don't like it charging my a123's to 3.7V (aparently 3.8V is the maximum spec). If I could adjust it down to 3.5V/cell (like you can on all the cheap sh!tty chinese ones for some reason) then i could run 5s A123 without worrying through my mamba speed controls (rated for 12 cell nickel) and only loose a few mah.