When I first received the Hyper Tough 20V Max Lithium Ion Reciprocation Saw, I put it on charge till the red light was off, and the green light was solid , and no longer flashing. I then used it on a small (aprox. 5 inch round) tree that I have been wanting to remove. It took about 20 minutes to take down, but in the mean time the Saw became hot, and stopped working. I let it cool down finished the job, then the battery died. I did expect this to happen because in the booklet, it states the battery will reach Full performance after about five charge/discharge cycles (so have patience with it). It also states to charge it for 7 hrs before using the first time, I missed that step.
The reason for the overheating , and shutdown is because I tried to push it too fast, and it went down, this is a safety feature according to the booklet. This so the battery or the Saw does not get overworked on shabby battery current, and fail too soon , and need a new replacement. The battery, and charger may become warm to the touch when charging, but the instruction booklet say's this is normal. To change the blade, you need to turn a circular knob to add, and remove it, it is a little hard to do so due to it is such a small area, but it doable. If the battery does hold longer charge after several cycles then I do reccomend it for small jobs.