i agree with that. that is a well built charger. more reliable than most. i now recommend bypassing the switch to turn the charger on and off. i think the impedance of the wires from the base resistor to the switch and back to the base of the transistor shifts the transistors a little out of phase in the oscillator and that makes it run hotter, so it is not an approved circuit by me anymore.
i think that is why they blow up the high side npn power transistor. especially at the high frequency of the circuit. plus use it on 240V if you can. i use the 600W model and i am gonna modify mine too when i can but mine is the 600W model, and i rarely do stuff until i have to or fixing something at the same time.
i charge to 88.3V on it. 6.5A. but i believe in slow charging. the lipo packs are expensive for me so i want them to last a long time, and be repairable too, i found out.
i could afford to build the lifepo4 pack from seconds i bot up dead from people here and ian gave me some. that one i charge to 87V with a repaired EMC-1000 that pushes 11A. 1/8C. hehehe
i use the two packs connected in parallel at the drains of the BMS.