Charger popped mosfets, and inrush transistor.

[longwood]

Received my 25A 20s lithium charger after waiting what felt like forever.

It’s rated at 25a on 220v circuit
And 13/14a on 110v circuit.

I first tried it in a 110v circuit using provided adapter. No issues after 20 minutes.

I unplugged battery, unplugged charger. Switch to 220v circuit with 30 amp plug (dryer circuit) had them wire the matching plug I had (10-30p)

It ran for around 5-10 minutes, I felt it at the 5 minute mark and it was room temp. Had a work call, came back to charger 5 minutes later and it was off. And the 220v breaker was popped.

I checked everything, unplugged battery. Contacted seller, they said to see if charger still worked. As soon as I plugged charger into wall I heard a pop from inside.

When I opened it, I found (see photos) the mf72 20d25 inrush current limiting transistor exploded. The seller told me to check mosfets and they were also damaged.

Nothing else appears damaged.


Any input on what causes this? If they replace it (they are waiting to talk to there engineer AliExpress purchase) should I fear this happening again?

I am not proficient in circuit boards very much, how ever I could replace the mosfets and transistor (that’s as far as my skills go)

I am just worried about what caused the fault. My smaller charger worked before and after this without any faults.

Pack is a 20s31p and it was exactly at 72.1v when this happened. Bms is set to allow 75a of charging, as that’s what I see on regen at times (e moto)


So can this be fixed? Should it be fixed? Can it fixed to not happen again.

And does anyone offer this service?

 

[amberwolf]

It’s rated at 25a on 220v circuit
And 13/14a on 110v circuit.

Are you referring to the input current, or the output current? Input current should go down for higher input voltage.

I first tried it in a 110v circuit using provided adapter. No issues after 20 minutes.

I unplugged battery, unplugged charger. Switch to 220v circuit with 30 amp plug (dryer circuit) had them wire the matching plug I had (10-30p)

It ran for around 5-10 minutes, I felt it at the 5 minute mark and it was room temp. Had a work call, came back to charger 5 minutes later and it was off. And the 220v breaker was popped.

I checked everything, unplugged battery. Contacted seller, they said to see if charger still worked. As soon as I plugged charger into wall I heard a pop from inside.

When I opened it, I found (see photos) the mf72 20d25 inrush current limiting transistor exploded. The seller told me to check mosfets and they were also damaged.

Any input on what causes this? If they replace it (they are waiting to talk to there engineer AliExpress purchase) should I fear this happening again?

Cause could be design flaw, manufacturing error, inadequate parts for the design and use intent, etc. Not really much way to tell from here. Best guess is the FETs are not rated high enough voltage for the actual voltages seen on them at the higher input voltage, or the capacitors used to filter the AC to DC aren't sufficient to do it well enough, and the ripple was more than the FETs could take. But it could be other things including shorted transformer windings from overheating or insulation nicked in manufacturing, etc.

The pop was probably the ICL blowing up because the inrush current was too high for it to handle (thus heating too rapidly), likely due to the blown FETs (they usually fail shorted).

So can this be fixed? Should it be fixed? Can it fixed to not happen again.

Since the PCB appears to be at least partly embedded in some form of potting, it may be difficult to troubleshoot and repair. If it's just the FETs and ICL you could replace them without depotting it, but you'd have to solder the new parts to the legs of the old ones (after cutting the old ones off at their casings, leaving as much leg as possible to parallel with the new ones).

If it's not just those, then you'd have to begin testing to find the failure that caused the FETs to blow; it could be either upstream or downstream of them in the circuit.

Whether it can be fixed not to happen again depends on what's wrong and if it's just a bad part or a design problem, and if the part can be replaced or not, and if the design flaw (if any) can be found and fixed.