Parts for a Common Sense digital Charger

[Dovebird101]

Could someone please help me find these parts for my Common Sense Digital Charger? I was checking a friends battery voltage, and I reversed the polarity and fried a couple of electronic parts. They are on the blue circuit board and labeled Q11, Q12, Q13, Q14. I looked at other posts but the transistors had only 2 wires, where these transistors have 3 (2 from one side and 1 on the opposite side). I believe they are also called surface mount. An exact website and part number would be extremely helpful.

Thank you for your help!

[Accu157]

I looked at other posts but the transistors had only 2 wires, where these transistors have 3..

Thank you for your help!

If they only have 2 wires (or posts, whatever they're called), they're not transistors. ;) Anyway, break out a microscope or a sharp eye, and read the number on the part you need to replace and the color. Take a photograph if you can.

http://en.wikipedia.org/wiki/Surface-mount_technology

That is the limit of the help I can provide. You will need to wait for someone else to chime in to tell us where we can buy these parts, actually, I'd like to know too. :p I know you may have to spend like 2-5 dollars on several hundred of those things. But bear in mind, you may replace the component, but you may have fried the chip as well, so if it doesn't work after replacing the parts... I suppose you could send it back in.

Are these good places to get parts from?
http://www.allelectronics.com/
http://www.halted.com/
http://www.smdinc.com/

Where are the websites where you just pick your part and buy the thing you want? I don't want to log in or sign a business deal, I just want to buy some stuff. When I get around to actually needing the stuff.

Oh, wait, are those Q11-# the names of the parts you need to replace?

[bearcreek]

Yes, it may be hard to find an exact replacement part. I believe there is a surface mount cross-reference directory on the internet or you could try googling the number. I often replace surface mount semiconductors with those big generic transistors from junked electronics or my local electronic store.

If you could show us a close-up photo of the circuit board we may be able to understand the circuit and guess at what the transistors do or what may work as a replacement.

[Probedude]

Could someone please help me find these parts for my Common Sense Digital Charger? I was checking a friends battery voltage, and I reversed the polarity and fried a couple of electronic parts. They are on the blue circuit board and labeled Q11, Q12, Q13, Q14. I looked at other posts but the transistors had only 2 wires, where these transistors have 3 (2 from one side and 1 on the opposite side). I believe they are also called surface mount. An exact website and part number would be extremely helpful.

Thank you for your help!

Picture would help too of where they are.

[Dovebird101]

[IMG]Sorry about that, I should have attached a picture to begin with.
I was hesitant to try to mention the number on them because I do not have a microscope and it is small. The number on it is probably S00. I cannot tell for certain, but the symbol next to it might be a degree or ohms symbol. The numbers could also be 500, 005, or 00S. The parts are black, but Q11 and Q13 are white on the left side where they shorted out.

Thank you for your help.

[bearcreek]

It looks like they are very close to the Lipo battery connection, right? Could they be power output transistors that control the charge current? If you have a voltmeter and carefully connect it between each lipo cell terminal and transistor pin you could see if the voltages are what would be expected for such a circuit. I recently replaced a mosfet in a similar 4s charger and it seems to work okay now. Are there large capacitors near those transistors on the other side of the board where the large solder pads go through?

[Dovebird101]

They are very close to the Lipo battery connection (white and green connectors at the bottom of the picture. There are resistors on the other side nearby that were adjustable before the dial was hot glued in place. Did your mosfet have three connections like this one? If so, what did you use? At this point I will take any good suggestion to try to get the charger working.

Thank you for helping me figure this out.

[Dovebird101]

There are also large capacitors on the other side nearby (1000 uf and 470 uf).

Thank you for looking into this

[bearcreek]

No, my mosfet had 8-pins and I used a big (not surface mount) 3-pin one from digikey.com to replace it.

It is hard for me to see in the photo what the transistor pins are tracing to, but it looks like 2 pins of each transistor are connected directly to opposite sides of each lipo cell, is this correct? I wonder if it could be meant to discharge (or balance) the cells?

It might be possible to use a transistor from your local Radio Shack (or other electronic store) to replace it if it is a typical transistor.

So did you say you plugged a Lipo cell into the charger backwards?

Have you tried using the charger and see if the other 2 cell charging sections (without the burned transistors) are functional? (be careful as something else could get damaged)

[Dovebird101]

When I connect a 3 cell battery to it, the display shows 3.0 volts for cells 1 and 3 and no display on cell 2. Yes, I plugged in a friend's battery to check the voltages and the black wire was on the opposite side. Basically I was rushing to get back into the air and was not paying enough attention.

Thank you for your help

[bearcreek]

That sounds like it could have caused quite a bit of damage. Do you know if it is normal for there to be no display for cell 2? Maybe you could check the voltage of your cells with another voltmeter to compare.

If we can't find the part number of the transistors then we may need to figure out the purpose of those transistors by inspecting the circuit (and it is difficult with the photo) like maybe probe the circuit with a voltmeter while the power is on.

If you can determine the polarity of the circuit around the transistor then we could figure out the pinouts of the transistor and a substitute possibly identified.

Do you know which displays are affected by the shorted transistors? (1 & 3) or 2? Maybe the different displays are a result of the shorted transistors.

[Dovebird101]

I did some testing with a voltmeter and I will describe it by labeling 1 through 3 starting with the top left connection, going clockwise, and ending with 3 on the bottom. I checked the resistance first, without 12v source or Lipo connected. The burnt ones crumbled when I tried to unsolder them so I assume Q14 is still a functioning part out of the four. The meter displayed 562 between contacts 1 and 3. 1183 between 2 and 3. The meter also displayed 1015 between all 1 and 2 contacts whether or not the part was there. Then I attached a 3 cell fully charged lipo without a 12 v power supply. Contact 3 was the negative and either 1 or 2 gave 4.15 whether or not the part was present. The other change I saw was the resistance dropped to 210 between 1 and 2 with the battery attached. I tried to charge, but it just shows 3.0 L for cells 1 and 2.

I certainly appreciate your help with this.

[bearcreek]

Maybe they are PNP transistors and are related to the voltage display. The resistance reading when the battery is connected is just measuring voltage, so it doesn't really show resistance. I expect that battery charger will not charge if it thinks one cell is at a very low voltage. It is strange that the displays are reading 3.0v if the cells are 4.15v. If the transistors are the reason for the strange 3.0v display, then pin 1 may be an output from the transistor and it may be interesting to test putting a resistor between pins 1 and 3 or 1 and 2 to see if the charger's display changes.

If you can test Q14's pin 1 voltage with and without a 12v power source supplied to the charger and with and without a lipo cell connected to this charge section that may be the most important test.

[Probedude]

Looks like Q14 is still intact. Get a closeup and clear picture of it so we can read the markings.

Dave

[cmulder]

i just had the charger near me and my camera can do close up so here goes

[Dovebird101]

Thank you CMulder, I could not get my camera to take a closer picture without it becoming fuzzy. What do you think, 00S or OO5? I have been looking at it with a magnifying glass, but the inscription is not clear, especially those symbols to the left on your picture.

Bearcreek, I cleared away the burnt parts and now when I hook up a 3 cell lipo it does not read any voltage on the digital meters. The display still works somewhat because I can change the amp charge. Without a battery (and with 12 v connected) I do not get any voltage on pin 1, and with a lipo battery connected I still get 4.15.

Anyway, I have probably taken up enough of your time and I appreciate your help. At this point I was hoping to fix this one and give it to a friend. I contacted Common Sense RC last week and bought another charger at a discount, but they could not locate the part I need even after the purchase. I will bug them some more and eventually they may figure it out. If someone recognizes it, that would be great, otherwise everyone needs use their time to make sure their planes are ready for spring and do not worry about my mistakes.

Thank you

[bearcreek]

I am also curious if these smd parts can be identified or purchased, as I try to repair devices with smd parts. It looks like S00 to me and I found a 3.8 amp N-channel mosfet w/datasheet here http://www.datasheet4u.com/html/W/T/-/WT-2300_WeitronTechnology.pdf.html that appears to have the same marking and same SOT-23 case.

But what I don't understand is it appears that the gate pin would connect directly to the positive terminal of a lipo cell and the drain pin to the negative lipo terminal. Could this be designed to work like a reverse protection diode?

[Dovebird101]

I was just about to give up, and you found the part, thank you. Tell me if you know of a place to buy it. I did some searching and could not find it so far.

Pin 3 is the negative and the others positive. Maybe it is like a fuse for reverse polarity protection.

I do not know if it acting like a diode makes sense because I do not know that much about electronics. I hope by replacing the burnt parts will fix it.

Thanks

[KaneTheMediocr]

I've used allelectronics.com before, never had any problems. That said, much of their stuff is still sitting in a bag, so I could have gotten a bunch of defective stuff and not know it.

[bearcreek]

Yes, I think that charger is advertised as having reverse polarity protection :(

It may be possible that something else could be wrong with the charger, so I would usually test a circuit like this by placing a low value resistor between the source and drain to see if the charger works properly before ordering parts.

The charger might work fine if you just short circuited the source to drain with a piece of wire, but that could be dangerous.

You probably do not need the exact same part. This mosfet from digi-key looks like it would substitute: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=SI2312BDS-T1-E3CT-ND

But you may want to take a closer look at the datasheets to be sure.

[jeffs555]

But what I don't understand is it appears that the gate pin would connect directly to the positive terminal of a lipo cell and the drain pin to the negative lipo terminal. Could this be designed to work like a reverse protection diode?

Yes, this would be a typical connection for a reverse polarity protection circuit. http://www.geofex.com/Article_Folders/mosswitch/mosswitch.htm

[Dovebird101]

I am ordering that part from Digikey (4 of them). For about $10 it is worth a try. Once I get the part I will solder it (better sharpen my iron) and report back if it worked or not.

Thanks guys for your help

[Probedude]

I am ordering that part from Digikey (4 of them). For about $10 it is worth a try. Once I get the part I will solder it (better sharpen my iron) and report back if it worked or not.

Thanks guys for your help
See if Mouser has the same or similar parts. Digikey charges a $5.00 service fee for orders less than $25.

[Dovebird101]

It works! Those were the correct parts. It has been awhile since I soldered such small components and I melted the second one I tried to install and ended up using all four that I ordered ( I was shaking quite a bit installing the last one knowing it would be another week if melted it, which did not help). It now works as always. I bet others will also benefit from your solution. Thank you very much everyone.

[bearcreek]

That is great to hear. I am glad that there were not more melted components. I can't figure out exactly why they blew from the reversed battery though. If the specs are slightly different on those mosfets I wonder if the cell balancing voltage might be a tiny bit different, but it might not be significant. I am glad we could help.

Cheers,
John

[rampman]

If they are off some the POT's can trim them back to specs.
Glad to hear it works.

Rick

[Dovebird101]

I have been charging batteries and then attaching a "Blinky" to them for final balancing. The Blinky does not blink at all after charging, so the cells must be balanced. I also tried another charger to top it off in case it was not charging all the way, and it will not charge the battery anymore. I believe this is as good as it gets.

Thank you