Ryobi 12v Li-Ion Battery Charger dead

[Agent24]

Re: Ryobi 12v Li-Ion Battery Charger dead

Sorry I didn't have a chance to complete this repair yet. Now I re-tested the removed cap, and it shown 0 Ohms in both directions, and also meter emitted sound on "short" test both ways. Does it confirm "tin whiskers" theory? I don't see them on the board. Despite all this, it measured 250uF stable capacitance versus 220uF rated. How is it possible?

I doubt it is tin whiskers. I don't think they grow inside capacitors... usually they grow on the solder terminals outside.

It seems strange it could measure shorted and still test OK with capacitance. I don't understand that, unless it just has a really high leakage current or something.

Open question however remains, why did it die prematurely without being used...

Same way anything does... sometimes it just happens.

[budm]

Re: Ryobi 12v Li-Ion Battery Charger dead

No it does not make sense, something is not being measuring correctly some where, it is like measuring a piece of copper wire and it show lots of capacitance.

[ben7]

Re: Ryobi 12v Li-Ion Battery Charger dead

It seems strange it could measure shorted and still test OK with capacitance. I don't understand that, unless it just has a really high leakage current or something.

My guess would be reduced breakdown voltage. The meter doesn't test with a high voltage (high as in more than a few volts), so it seems fine when measuring the capacitance, but it breaks down (high leakage current) at the circuit's operating voltage.

I'll get C203 cap replacement. Yes, its 0.2 Ohms reading went away once removed from the board, but... I can't say what it is now. Once out and fully discharged, it measures from 30 kOhms slowly growing to 2 mOhms, then suddenly drops back to 15-30 kOhms, and start growing again towards mOhms. Is it normal for caps? I assume its bad, since without it the charger shown signs of life?

I think you must have meant mega-ohms instead of milli-ohms. I use MOhms for mega-ohms, and mOhms for milli-ohms.
It sounds like either your probes have a bad connection to the cap, or the cap's dielectric is breaking down, causing it to discharge what little voltage/energy that accumulates from the resistance test.

[sambul83]

Re: Ryobi 12v Li-Ion Battery Charger dead

I would replace C203 first and see what happen, without that high capacitance in place the circuit may be oscillating.

Sorry for the late update, I finally got a hold of new adjustable soldering iron, replaced C203 cap as suggested, and the charger is now working like new again - already fully charged 2 batteries. Ryobi service told me earlier, they don't repair chargers out of warranty, just buy the new one for $40. Amazingly, just one 30 cents cap replaced, and the charger is "brand new" again. Appreciate budm and other guys for help in this matter.

[sam_sam_sam]

Re: Ryobi 12v Li-Ion Battery Charger dead

Thanks for sharing your work


I have one Ryobi 18 Li-Ion Battery Charger that is dead and have not had the time to trouble shoot what wrong with is but it is doing the same thing no LEDs are lighting up

When I have some time to work on this board again I have a good idea where to start

[Crazyfrog]

Re: Ryobi 12v Li-Ion Battery Charger dead

What an excellent discussion I just used the info here to go through my dead BCL-1200 charger and found the issue to be that voltage was coming in at 230v passing through fuses diodes, NTC 10ohm thermistor and caps getting rectified to 340dc and not getting any further with caps further into the circuit at 0v. The issue was the TOP245YN which is meant to convert the 340v dc to 12v which didn’t do anything. There was 0v on the control pin so I also changed R104 and R103 which are meant to provide a 5.8v turn on signal to the TOP245YN. I changed both resistors and voltage converter as i could see a zero load 110v on r104 with one side lifted from the board.
I intend on replacing the electrolytic caps with Samsung caps or similar branded as these are my best guess for the TOP245YN and it would be great to know this will be reliable. I also intend on buying a capacitor tester to see how worn my rusty disused charger capacitors are.

[stj]

Re: Ryobi 12v Li-Ion Battery Charger dead

samsung are crap, use panasonic FR series or rubycon ZL series
but not for the big mains cap - that needs to be something like a rubycon BXW