I attached both the power cord and charger leads successfully to the unit - no flames, blow ups or shock therapy. With my multimeter I tested the voltage and found it set at 17. Using the adjustment screw for the voltage I found left near the green LED, I found the lowest setting was 14 and the highest 20. Connecting my 4 in 1 charger to this power supply resulted in the over voltage protection alarm to came on. My charger is shot and out dated after years of constant use. That's why I can't use it. I rated this unit 5 stars since the voltage is 20 volts as stated.