Behold, my new 400w 5S-14S charger
Its a meanwell s350-48. Zeners are left untouched so it has an upper limit of 58v.
The thermistor has been replaced with a resistor so the fan is on constantly. That should keep things cool.
Current is fixed at around 8 amps at the moment with a shunt mod, I don't really have any need for variable current at this stage.
What I do need is variable voltage, so I removed SVR1 and replaced it with a precision 2k pot. I'm not sure how many turns it is but one complete turn gives me a resolution of about 1.5v so I can quite accurately set it down to 10 millivolts. With the 2k pot alone i was able to turn the voltage down to 31v, but I needed to go lower if I want to charge individual 5 and 6S packs. So I added a switch (the second knob) that adds another 2k resistor in series. This drops the voltage down to a minimum of 20.5v. You could achieve the same with a single 5k pot, but I didnt have one handy and I actually like having a high and low range switch and then the fine tune.
I don't think anyone has had one of these 48v units running voltage this low before so I'll report back if I have any issues.
The only thing I've noticed so far in a quick test is that the fan speed drops when I flick to low voltage mode