Repair of Fuyuang 55V 250VA Li-ion charger
A not working (of course) LI-ION charger was brought to me for an inspection. And someone probably shorted this charger because they assumably changed the in and out cables when plugging in to the 230VAC power grid. (Because the ingoing and outgoing plug “Mickey Mouse- they are called- if I’m correctly informed” of the charger looked completely identical !).
It was a 55V Li-ion Battery charger with a heavy 2.5 Ampere current and 250VA Power 100- 240V 50-60Hz circuit.
(Output 48VDC 2.5 Ampere : See photo sticker bottom box below text).
Opening of the box was only possible after cracking open the plastic top and bottom sides with the right screwdriver. (like it is often the case). The result was the next photo showing the copper solder side of the pcb.
And the next Photo explains why I still couldn’t see the components.
Because there were 2 Aluminium bended Cooling profiles on top. I had to desolder the one with the attached Power Mosfet, to be able to see the components in charge (at least they where before it broke down! Haha).
After removing the Alu profile I could oversee all components. And it turned out that the Mosfet (of type 20N60 C3) was shorted on all pins and 1 or 2 resistor’s had gone too in the
circuit of the PWM controller (a LD 7550B IC PWM Green controller). Just as the Fuse (a 3.15 AT 250VAC bigger 32 mm type with solder wires).
The above mentioned Green PWM Controller LD 7550B is an 8 pins DIP chip. Soldered left from the middle of the pcb right under the 20N60C3 Mosfet. On the right side of the Mosfet there is the Reservoir Elco that holds a firm 320 Volts DC or more when charged. And only the Fuse, , the Mosfet and the 8 dip controller, plus 1 or 2 resistors around the controller were blown. I replaced the Mosfet and the controller and other defect parts. And before testing it live on the 230 VAC 50 Hz grid, I of course used a bulb of 60 Watts 230 VAC which I placed over the wires of the blown fuse. To prevent a big power surge from happening and blowing up everything in the fuse box at home, including the already replaced components – in case if the charger still was shorted or malfunctioning !
The above picture shows the High Voltage Elco and left under top of the Mosfet 20N60C3. And completely on the left we can still see a bit of the replaced LD 7550B controller.
The red tape on the right shows the replaced 3.15 AT fuse.
As we can see this is the 230 V input charger side. With the Graetz diodes and the filter above in the photo. The safe 55 Volt charging side is on the left side from the Transformer.
The next photo shows the 8 pins power controller IC (top view) and on the right we can see the top of the Mosfet 20N60C3. In the black shrink tube below was one of the defective resister’s I also replaced.
The above picture shows the charger secondary “Safe side” with the Optocoupler (a 4 pins type chip).
And above photo shows the top view of the Transformer and the secondary side. The Mosfet lookalike below on the right was 100% okay when tested with the diode test on my meter and not part of the primary circuit side. And is surely a Dual Power Diode. And both its outer pins had a ferrite.
The picture below shows the replaced Power Mosfet 20N60C3. To be exact we must notice the ferrit on the middle pin of our Mosfet. (To prevent it from oscillating …).
After a final bulb test it proved that this charger worked again splendidly. And later I found out that this kind of chargers also exist with twice the power of this charger current. (5 Amps and 55 Volt => for 48 Volt Li-ion). And they are used for electric scooters !
This charger was for someone’s electric transporting device, but since I never saw it I’m not sure what it exactly was, or how it looked. But their charger was as new again !
Mission accomplished as the Jestine Site often states !!
On the above page I’ll finally show the top and bottom of the Charger box and its “Mickey Mouse” Cable.
And above photo demonstrates that the Supply really works !
Good luck in repairing !
Albert van Bemmelen, Weert, The Netherlands.
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