Repair of Ryobi BCL14181H Li-Ion charger

[WaynesWorld]

I was recently given this non working charger.

It has been 25 years since I did my AD Electronics and about as long since I did anything with it, and for some reason my interest in electronics has been rekindled recently and I'm absorbing anything I can learn. Dave's Fundamental Fridays and repair videos are great sustenance.

The process so far...

Circuit seems to be rectifying on at the 240v level. Does this mean its a Switch mode?
Power on - No lights. Not charging
Open up
General look around - nothing immediately obvious
Check fuse - Open circuit
Replace fuse - fuse blew
Found all 4 rectifier diodes short circuit
Replaced all 4
Powered on - blew fuse and 2 of the diodes
Looked some more and found NTC blown and 0.47R on DC side blown to high resistance (edit - 0.43Ohm)
Here is the top and bottom of the board showing the above mentioned components.

I have tested pretty much all the diodes including zeners on the bottom. I can't read the chip numbers.

Is there anything else I should check or test and is there something else likely to have caused these devices to fail?
Can the NTC be substituted for something else as a temp fix?

[coromonadalix]

if the fuse has blown  check the transistor on the dissipator plate,  could / should be an mosfet,  remove it and check for shorts between the pins

[WaynesWorld]

You're on the money. Shortly after posting, I traced the resistor to the Source of the ndf04n60zh on the heatsink. The D and S were shorted. The tranny seems to test OK across each coil and all the local diodes and capacitors test good to. Anything else I should look for?

This MOSFET seems to be unavailable in Australia. 3 months via Aliexpress, so hoping for a local substitute.

[ElektroQuark]

Do I see a crack on that IC?

[WaynesWorld]

I did notice that but put it down to just a physical nick, but you could be right. I've taken the best photo I can with my rubbish OPPO phone using Open Camera, highest res, macro focus, zoomed, and cropped to keep the file size down. I don't have a decent magnifying glass to read the part number properly. Maybe someone recognises the number from what's visible?

[Pete66]

That's a Mosfet and it looks like it is blown.  Measure to see if it is shorted.
If its blown I think its this one:

9565bgh

https://www.ebay.com/itm/10pcs-AP9565BGH-9565BGH-TO252/254599070987?hash=item3b4749850b:g:6tgAAOSwal5YMUmh

[WaynesWorld]

Its completely open circuit between all legs in all directions on Ohms and Diode test. Safe bet its F*$%ed. I might see what its connected to and do some tests.

[WaynesWorld]

I spoke to soon. I retested and got 2.4v across S-G. I lifted one side of the Zener and it is OC both ways. I still got the 2.4v across S-G. What does this say about the MOSFET? edit: according to the datasheet, I should at least get 0.6v across D-S but that's OC so I'm guessing dead.

How do I work out the zener value? Too small for me to see.

[Pete66]

I found this thread:
https://www.ifixit.com/Answers/View/261271/Why+doesn%27t+my+charger+work

According to them it is an 18V Zener

[WaynesWorld]

Thank you. I did come across that page a few days ago, before I had discovered all the destruction, so dismissed it, and didn't scroll down enough to see all the responses. Now though, I think it will be a wealth of info. I'll spend some time collating the info and see what I need to test and order. Hopefully those schematics will be useful to.

They talk about how rubbish the circuit is and that it has no protection. Is there any straight forward mods I can do to improve it's longevity? Or do I just order a bunch of each part and replace them every time it fails?

[Pete66]

I would replace with a more powerful Mosfet.  The 9565bgh can handle -40V and -17A.
I would  use a P-channel Mosfet that can handle more current.

[WaynesWorld]

Good advice. I'm also going to add a piece of aluminium as a heat sink. For normal operation charging 18v batteries that should be ample, but I guess its the abnormal situations due to the crappy design that causes the issues.

I'd like to identify and test PC1 as its right in the mix. Its a 4 leg package and I don't know what it is. The number looks to be something like L1343. Any clue?

What's sources are there for these MOSFETS in Australia?

[orbanp]

While you are at it, you might want to replace that electrolytic capacitor, on the top of the board, next to the diodes. The top seems to be bulging a bit.
Regards, Peter

[WaynesWorld]

That one tested OK. It's just the way the light reflects off the prisms in each quadrant.

[Pete66]

PC1 is an optocoupler.  It's for feedback from secondary to primary.

[WaynesWorld]

Any clue on the part number so I can find a data sheet for test and replacement if I need?

I removed it from the board and did the 2 x multi meter diode test and it seemed to work OK, so I put it back in.

I'm looking for replacements for the NDF04N60ZH and 9565bgh.

For the NDF04N60ZH
Mouser suggests the FDPF5N60NZ as a 'similar product' however, the 5N has a lower continuous and pulsed drain current, and the zeners are opposite.

The NDF04N60ZH seems to have a fancy structure with the diode across the S-D and opposing zeners across the G-S. Is there a special term or technology type, search term etc for this setup? Or does it not really matter? I can't find info or videos to explain the purpose and characteristics of these extras.

The 9565bgh is not listed on Mouser. Looks like the FDD4685 is the choice replacement with more than double the Pd and Current Dains.

[Gyro]

Good advice. I'm also going to add a piece of aluminium as a heat sink. For normal operation charging 18v batteries that should be ample, but I guess its the abnormal situations due to the crappy design that causes the issues.

I'd like to identify and test PC1 as its right in the mix. Its a 4 leg package and I don't know what it is. The number looks to be something like L1343. Any clue?

What's sources are there for these MOSFETS in Australia?

Be very careful that you don't compromise primary to secondary side safety clearances if adding metalwork inside a Class II product. Anything that reduces the clearance below 8mm is going to be a problem - especially for something like a drill charger that might get rough treatment.

[WaynesWorld]

For sure Gyro. I was simply going to glue a small square piece of flat aluminium (say 20mmx20mm) to it using a thermal glue of some sort, and then hot melt glue around the BAT+ pad. Gotta find suitable replacements for the components first though.

I just used Mouser to narrow down by type and package and interestingly, returned only 1 result...

SiHA6N80AE https://au.mouser.com/Semiconductors/Discrete-Semiconductors/Transistors/MOSFET/_/N-ax1sf?P=1z0z63xZ1z0y3zrZ1y95l6eZ1z0xzzgZ1yzxnag

It seems to have the same internal structure and better current and voltage specs, so looks like a winner. The only spec less is the 'Pulsed drain current' which is half that of the original (20A -> 10A). Is this an issue?

[thehwguy]

I too have a RYOBI BCL14181H dual chemistry charger and have noted a failure of D9 (short) and Q2 (MOSFET short). What is surprising is BOTH D3 & D9 (HBR5200) are connected in parallel to presumably share the charging current load of 1.8A. In my book it this is a "poor" design as it is likely that one of the parallel diodes will conduct the majority of the current load rather than having an equal current split. Another interesting point is that D3 & D9 are shrouded in yellow glue which will hamper the heat dissipation.

[GraemeG]

I realise that this is an old thread and hasn't been updated for more than a year but I think it makes more sense to continue this one rather than start a new topic.

As with many of the other posters, I have a BCL14181H charger that has failed. Mine has S/N 005624 and was made in week 4 of 2014. Until recently it has been working perfectly but now totally dead.

Inside it was pretty obvious that Q2 (P-Ch MOSFET 9565) was cracked open and smoked! Further testing found one of the D3/D9 diode pair shorted and the main switching regulator Q1 (N-CH MOSFET NDF04N60ZH) open circuit. I have tested many other components, mostly in circuit, but I don't think anything else has failed. I have attached a couple of sections of the circuit diagram as far as I have been able to trace.

I am waiting on parts to be arrive from China so I don't yet know how successful this repair will be but I thought it worth documenting as I go.

I chose the IRFR5305 (Edit: corrected this part number) as a replacement for the 9565, it has a higher Vdss at 55V vs 40 and a higher Id of 31A vs 17A. From eBay I found 10 pieces including shipping for USD4.33 to Australia.

The D3/D9 diodes often seem to fail and in looking for a higher rated diode decided to go with the MBR20200CT, a pair of diodes in a single TO-220 package. I will mount these as a parallel pair like the originals but even individually these diodes have higher ratings at 20A vs 5A for the original MBR5200 and the same Vreverse of 200V. Another 10 pieces for USD3.85 including shipping.

For the NDF04N60Z I stayed with the original part and ordered 10 pieces for USD12.43 delivered.

I have a few tips for troubleshooting these units so there will be more posts to follow and I'll let you know how it goes when the replacement parts arrive.

[GraemeG]

Before I ordered parts I wanted to be fairly confident that there were no more failed components on the board. The most likely candidates are components connected to or close to the failed parts that have already been found.

Checking around Q2 it was easy enough to meter R11, R12 and ZD2 in circuit. I didn't check the zener in detail but it is still acting as a diode so it is probably still a functional zener. I used a simple multimeter diode test to check it forward and reverse. The multimeter is not a high enough voltage for the zener to conduct so it shows as open circuit in the reverse direction just like a normal diode.

I was able to use 2 multimeters in their diode test modes to check the FET Q4. I attached both meter negative (black) leads to the BAT- terminal which is connected to the Source of Q4. The positive (red) lead of one meter was then connected to the Drain or to R12 or the empty Gate terminal of Q2. Note that Q2 is still removed from the board. This meter should show no conduction/connection through Q4. Then the positive (red) lead of the second meter is touched to the Gate of Q4 and the first meter should show Q4 is now conducting. Removing the meter from the Gate should show Q4 open circuit again. One catch I have found is that one of my meters applies 1.5V in diode test mode while the other applies 2.5V. The 1.5V meter is not always high enough to drive the gate of a FET so I use this one across Drain-Source and the 2.5V meter on the gate.

I used a similar approach around Q1, metering the various resistors and diodes mostly showed reasonable values. One exception is D1. The low value resistors R3 22 ohms and R4 150 ohms make it difficult to test this one in circuit. It appeared short circuited so I removed it only to find it is working just fine. That's when I realised R3 and R4 were causing the problem. I used the 2 multimeters again to confirm the opto isolator PC1 was functional. Again I had to use the higher voltage meter to drive the diode and the lower voltage unit worked fine on the transistor side.

My last concern was with IC1. This IC drives the gate of Q1 and if the IC is dead and the output driven high it would simply turn Q1 hard on and probably destroy it again. IC1 needs at least 13-14V minimum to start up and operate. To give some level of protection I set my bench supply to 18V and connected it through a 2K7 resistor (2700 ohms but not critical) to EC2, the 10uF electrolytic capacitor that supplies Vcc to IC1. In the attached screen capture from the oscilloscope IC1_Vcc+output_to_Q1_gate.jpg you can see the green Vcc trace increases to about 14V then the IC starts up and outputs a square wave for about 50mS then shuts down. This is normal protection behaviour of the IC. Q1 is out of the circuit so the transformer is not driven and the IC has not detected any feedback on pin 2 from the opto isolator. We can confirm that in the screen capture IC1_Vcc+pin2_Comp_Feedback.jpg. The pin is sitting at 5V from the internal bias supply. The final screen capture IC1_output_to_Q1_gate.jpg is a closer view of the output pulse train that will drive Q1. The output looks good and is running at about 65.8kHz which is pretty close to the nominal 68kHz that a 100K R1 resistor on pin3 should produce.

So it all looks good and now all I need are the replacement parts. I will have to be patient, I think the bits are still a couple of weeks away...

[Greybeard]

If anybody needs schematic, see attachment.
I found it in the www some time ago, when I repaired my charger.

Defective parts of my charger:
D3 or D9 (shorted)
Power MOSFET Q2 (shorted, case cracked)

[GraemeG]

Thanks very much Greybeard! I had not seen that circuit before. There are slight differences with my unit, there are a few differences in component numbers and I also have a 20K resistor from G to S of Q1 on mine. But mostly it seems to match up so far.
I'm still waiting for parts and have a quiet day today so I plan to try powering up the 5V regulator and see what happens on that side of the circuit. I expect the controller should show some sign of life.

[GraemeG]

To see if I could test any more of the circuit I supplied 8V from my bench power supply to the input of IC4 the 5V regulator. As expected it supplied 5V on the output and the red LED turned on. This is the correct indication for a charger with no battery connected so it's a good sign!

Everything else seemed to be effectively shut down. All the outputs of the quad op amp IC2 were low but I used a 100K resistor from the 5V rail and carefully probed each of the op amp + inputs. This was enough to drive the output high except for IC2C. On pin 10 there is a 1K resistor to ground so I grabbed a handy 4K7 resistor in place of the 100K to toggle the output. Now I know all four op amps are still working.

I was able to use the same method to check Q3, Q6 and Q9 although they had all previously measured ok in circuit. For bipolar transistors as long as I can measure 2 diode junctions (base-emitter and base-collector) in circuit using a multimeter then it's likely the transistor is still ok. But switching them on and off while powered up in circuit pretty much guarantees they are still functional.

So I think that is it for the testing until the replacement parts arrive.

[GraemeG]

I am still waiting on the MBR20200CT diodes but the NDF04N60ZH and IRFR5305 (Edit: corrected this part number) MOSFETs have arrived.

It turns out that the original NDF04N60 has not failed!

I discovered recently during another repair https://www.eevblog.com/forum/repair/repair-of-hp-0957-2304-power-pack-for-hp-photosmart-7510-all-in-one/msg4615453/#msg4615453 that the method I use to test MOSFETs with my multimeter is not reliable. It seems that some power MOSFETs, in particular high voltage devices, need more than the 2.5V that my multimeter can provide to turn on the gate. I now add a 1.5V battery in series with the test leads of my multimeter or use the very handy Multifunction Tester to verify these devices (see photo). There are a whole range of these devices available on the internet for just a few dollars, all based on an "open source" project, and they are really very effective.

So the only components that now appear to have failed are the D3/D9 diode and the Q2 9565 MOSFET. Others have speculated that Q2 needs extra cooling or is under spec'ed, possibly because the common failure mode is to find a hole blown in this device! But looking at my circuit board I don't see any sign of long term heat around Q2 but it is definitely visible around D3/D9. In the photo of the back of the board in the original post by WaynesWorld and in the photo I have attached to this post you can see the brown discolouring around D3/D9 but there is no sign of this around Q2.

My theory is that D3/D9 goes short circuit and then dramatically kills Q2 which explosively blows open.