40
The 18650 lithium battery is 3.7V 3Ah. Use 40 batteries and connect each 10 in series to become 37V 3Ah per group. Then these 4 groups are connected in parallel to become 37 V 12 Ah. very embarrassing. Ah, 40 batteries need to be soldered with a soldering iron, and if an individual battery has problems, it will affect the overall performance.