Built a 2.2kWh 18650 pack as a project during my year off from school. Was intended for use in an RV and to be charged with solar power. No solder was used in it's construction except in the wiring of the BMS leads. I used a 50A 3S bms I got of Aliexpress. Was put together with cheap nickel-plated strip using a homemade microwave oven transformer spot welder. Works well with a tracer 4125 bn solar controller where you can adjust the voltage values.