The importance of potting mobile chargers

[auraslip]

Especially the cheaper plastic chinese ones. There is only so much bouncing the leads on an unsupported capacitor can take before it snaps.

Back history though; after a few months this charger died. I replaced the cap with a larger one I had laying around and hot glued it down. (Is that the right thing to use for potting?)

It worked for a month and then went dead again. (This is on a daily rider with the charger going everywhere!)

Opened it to fix it, and the fuse was blown.What I first noticed was that the fet and heat sink in the top right was not properly potted like the fet and heat sink on the bottom left. The solder joints had cracked from the heat sinks bouncing and wiggling, so I fixed all that.

I didn't notice it but the IC in the top right of the first photo was already smoked. So when I replaced the fuse, I got a nice plasma ball from it.


Burned up IC - what is it?

Also, note the scorched resistors and diode bottom mid-right. Resistance is too low on those, and they feed into the burnt IC.



Scorched here too on the trace side.


extra shots of parts.

 

[auraslip]

dumb

 

[auraslip]

Um... so I'm a big idiot. I wired the new cap in backwards.

Honestly, I'm pretty dumb. Funny thing is that it worked for a FEW weeks.

Anyways, could anyone open up there charger and see what IC I burned out so that I can replace it?

 

[Doctorbass]

What i do on every power supply or charger and controller is to add some silicon on the base of every high components adn heavy components... and sometime between two parallel high components like big HV capacitors and transformer and heatsink.

Work really well !

The silicon not just hold these in place but it damp their natural resonant frequency.

I recommand this improvement on every ebike electronic stuff

Doc

 

[amberwolf]

Anyways, could anyone open up there charger and see what IC I burned out so that I can replace it?

Which charger is it? There are quite a lot of different designs, and they don't all use the same types of chips.

At 8 pins it could be an optoisolator, or a power control/SMPS startup chip, or an op-amp. Or a few other things less likely in an SMPS.

A pic of the charger case and label (if any) might help, too, in case someone has one that looks like yours and is the same inside, but is a different "brand".

 

[bearing]

EDIT: oh, so it wasn't the FET in the upper right corner that was broken, it was the IC next to it. If the IC is a gate driver, the FET may be the cause of the IC to fail.

2SK2605 ?
http://www.toshiba.com/taec/components2/Datasheet_Sync/77/3084.pdf

Can most likely be replaced with any TO220 NMOS with:
V_DSS >= 800V
RDS_ON <=1.9 ohm
Total gate charge ~34nC

 

[auraslip]

yeah... it was a one in a hundred shot that anyone would have some random "top electronics" brand charger.

I suppose I could analyze the circuit and figure out what it did, but if it's an op-amp or optocoupler, what are the odds the replacement part would work?

 

[bearing]

It's most likely some sort of controller IC, probably with a built in gate driver. An optocoupler would not be put there, it would be put just on the line between the HV and LV parts of the board. The big resistors which have run hot are probably charging the bypass capacitor next to IC just as you plug it in. Once the voltage on that capacitor is high enough that the IC starts, the IC will be feed from an auxiliary winding of the transformer. Those resistors will still get hot though, because they are not disconnected when the auxiliary winding starts feeding.

If you manage to figure out some of the pins on it, you might be able to find a similar controller, which might work.

 

[heathyoung]

I've found that the meanwells cope reasonably well with being transported around, the only problem I have had (regularly) in 3,000Klms is the stupid fan dissasembles itself from the impacts of riding (especially how I ride - I've bent 3 racks now, fixed with 3X25mm steel strap).

The impellor and circuit board come loose from the rest of the charger, and you have to take it apart, force the fan back together and its OK for a few more days. I'll replace the honky little fan with an 80mm version mounted on the top. Should allow a few more amps into the batteries as well.