Connect with us

Battery Chargers DOA Model HF #45005

Discussion in 'Troubleshooting and Repair' started by Woodman, Dec 3, 2012.

Scroll to continue with content
  1. Woodman

    Woodman

    47
    0
    Dec 3, 2012
    Hello gang!

    Recently I purchased two 6/12 volt battery chargers with 2 and 6 amp modes at EBAY. A liquidator was ditching for Harbor Freight, made by Chicago Electric. Retail is $60 for both and I paid $19 for both including shipping knowing that both were not working. Thought I could get at least one if not both going and now am having some problems. Manual states they don't sell replaceable parts, and I have at least one bad part. The diode in the bottom right corner of first BAT charger (see pic of circuit board) gets very hot when plugged into mains for a few seconds with battery attached. The board has two diodes labeled scr1 and scr2, and they are stamped as BT151 25J TRANSUN. Ebay sells similar SCRs for $4 including shipping. I suppose I could swap good diode from other charger but that one works fine.
    The second charger was also DOA originally. Noticed that there was no continuity on one of the primary leads so I moved to a different lead and now secondary output tests ok so one charger appears to be working already.


    Woody
     

    Attached Files:

    Last edited: Dec 30, 2012
  2. Woodman

    Woodman

    47
    0
    Dec 3, 2012
    mystery component

    Just thought of another question. If I peel back a layer of tape wrap on the primary there is a mysterious little rectangle box like device that I can't ID. The photo is a little shaded but on the top of this thing on either side there are two wires coming out of it. One attaches to the first of five primary leads and the other attaches to the last lead. As far as I can tell it just links both leads electronically. But there is no continuity between first and fifth lead. Also the first lead has no continuity between any of the other leads. What is this item?

    Both chargers were DOA, so to power them, I shifted the AC black mains live lead (moved live ac wire from 1st to 5th lead). The only thing I can think of, is that the wire has a bad connection to 1st lead on both battery chargers. This liquidator is selling these things by the truckload so I think there is definitely some quality control issues going on with these units. Most are being resold as working units, but a ton of them have also sold in pairs of two as not working.

    Woody

    UPDATE: As Dave explains below, this unkown item is a fuse between lead 1 and 5 that blew on both my chargers. If yours blew, the fuse should be replaced as it protects the transformer. I did not know there were any marking on it but when I clipped it off markings became visable with a mag.glass. It is rated at 2amps 240 volts and blows @ 130 centigrade.
     

    Attached Files:

    Last edited: Dec 30, 2012
  3. davenn

    davenn Moderator

    13,710
    1,911
    Sep 5, 2009
    welcome to the forums :)

    its a thermal fuse if its open circuit, then there will be no current flowing through the primary

    Dave
     
  4. Woodman

    Woodman

    47
    0
    Dec 3, 2012

    Dave, thanks for the welcome -great site you Aussies have here!

    Since my primary taps are open between taps 1 and 5 then I assume fuses on both chargers blew. I have several spare regular fuses on hand ranging from .2 to 30 amp -can I use one of these fuses to replace and what size would you recommend?


    Cheers,
    Woody
     
    Last edited: Dec 28, 2012
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    I'm sure the Australian moderators would love to take credit for this entire site, however this site is here thanks to Ian (who's British) and we have another moderator who is also German.

    You may have just visited us while us Aussies were awake and active :)
     
  6. Jotto

    Jotto

    120
    0
    Aug 24, 2012
    You can test the SCR's with a meter. If they are high voltage ones they won't stay shorted, but low voltage ones will.
     
  7. Woodman

    Woodman

    47
    0
    Dec 3, 2012
    Quality Control @ Chicago Electric

    UPDATE...

    I removed the board to examine with a glass, and noticed that two different, smaller power diodes were accidentally soldered together. A brief hot touch with hot solder wick remedied that problem. Now when I plug AC cord in, there is no smoking hot diode, and there are normal secondary transformer readings. HOWEVER, when I add/connect it to a live battery then the same large diode is still smoking hot.


    Woody
     
    Last edited: Dec 28, 2012
  8. Woodman

    Woodman

    47
    0
    Dec 3, 2012
    Before I order some diodes that may or may not even work, I remembered a "small" detail that I definitely should have mentioned. The attached pics show that the transformer on the non working BAT charger may have some shorted windings. Notice how the yellow wrapping around the primary windings looks like they may have melted a little.

    As previously stated, when I plug charger into mains, the secondary voltages are all good, but when a car battery is connected to DC output then that larger diode still gets very hot. The transformer does not get hot with just AC connected, and does not get hot with BAT added -though I only connected battery for a few seconds. Could this transformer be toast, and how do I test to see if it's toast?


    Woody

    PS for some reason could not post 2 pics and will try at another time, but wrap looks to be partially melted.
     
    Last edited: Dec 28, 2012
  9. Woodman

    Woodman

    47
    0
    Dec 3, 2012
    melted plastic wrap pics attached -toasted or ready-to-be toasted transformer?
     

    Attached Files:

    Last edited: Dec 5, 2012
  10. Woodman

    Woodman

    47
    0
    Dec 3, 2012
    Unidentified cracking sound ?

    Not sure if I mentioned this fact or not -- as per manual instructions, I hook mains AC first to charger then DC clips to battery. Now on mine, I always turn it off after a few seconds after battery connected because there is a loud cracking sound every time. Do you think that cracking sound is coming from the transformer or the hot diode?

    Woody
     
    Last edited: Dec 6, 2012
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    I'd be looking more closely at that hot diode. It may have been damaged, or another part close by may be damaged.

    I would be using a resistor (say a 10 ohm 20W resistor) as my load until I knew what was happening (if that doesn't work, try your battery in series with that resistor).
     
  12. Woodman

    Woodman

    47
    0
    Dec 3, 2012

    Steve, thanks for your reply again. I don't have any such resistor, but I have many old car dome light type bulbs. Okay if I "charge" bulbs as the load, and should I wait until new diodes arrive to test?


    Jotto, thanks for the reply also. I have ordered new high voltage SCRs. The bad diode had continuity in any direction tested with a multimeter on the diode setting. The good diodes tested with ohms in one direction and infinite resistance in two other directions. So I'm guessing that one diodes is toast and can no longer block voltages from a live car battery, and this is why when battery is connected diode gets ultra hot? Also not sure of SCR's amp rating of old, but new ones have 12 amps continuous duty.

    Since both boards are identical, I tested all twenty some components to see if anything else was wrong:

    1.The two smaller diodes test same on both boards
    2. All the resistors were within 10% tolerances
    3. Three unknown transistors test the same
    4. One of four power transistors on the good circuit board tested "leaky" -when compared to same measurement on the other board the good power transistor showed infinite ohms when tested in the diode mode. Of the eight total power transistors this was the only one that tested leaky and it is located on the charger that works.
    Now I'm wondering if I should order a replacement power transistor. Ebay sells generic power transistors. Not sure if they will work, and if all four should be replaced??


    Woody

    UPDATE: I found some numbers on back of power transistors and ordered exact replacement. Interestingly, three of the four power transistors on the two boards are different models. The one that is leaky has only 40 volt max transistors, while the other board has all 150 volt maximum capacity.
     
    Last edited: Dec 28, 2012
  13. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    Yes, a 12V lamp is a good substitute for a resistor.

    40V and 150W are two different things. They may be 40V AND 150W
     
  14. Woodman

    Woodman

    47
    0
    Dec 3, 2012

    Thanks for noting mistake. I highlighted and corrected in above post to 40 volt and 120 volt. Looks like this charger needs to see voltage from battery before it will output amps. Anyway to override this safety feature?
     
    Last edited: Dec 6, 2012
  15. Woodman

    Woodman

    47
    0
    Dec 3, 2012
    If anyone ever wants a picture of how board is supposed to look like here are pics front and back. It is complicated circuit having 13 resistors, 4 power transistors, 3 regular transistors, 2 SCRs, a pair of 1n4007 diodes, and a voltage regulator diode. Part numbers are on each component.
     

    Attached Files:

    Last edited: Dec 30, 2012
  16. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    That makes a lot more sense.

    The transistors probably only need to be rated at 40V. Maybe they ran out, or someone used the wrong part, or... (who knows)

    The lower voltage transistor probably performs better in the usual case.

    Place the lamp in series with your battery. The lamp will (help) prevent damaging currents from flowing either from the charger to the battery or vice versa. (I think I mentioned this very briefly above, but I didn't think you'd need to do it).
     
  17. Woodman

    Woodman

    47
    0
    Dec 3, 2012
    Steve, understood what you said the first time -the fuse/light would blow if amps were too high thereby protecting BAT and charger. What my question was, and I admit it was not at all asked very clearly, how to override the safety feature by altering the circuit board? This would be useful if using charger for another purpose like a power supply for bench testing or electroplating. I suppose easiest way would be to bypass circuit board completely and take voltages directly from the transformer, then bridge rectify it, and somehow use caps/resistors for smoother DC?
    Today I took voltage measurements on this center-taped secondary and found six different voltages ranging from about eight to 25 volts, and was thinking this could make a nice "stepping" power supply, especially since I have an extra one. Any suggestions on moding this to a PS?

    Thanks,
    Woody
     
    Last edited: Dec 28, 2012
  18. Woodman

    Woodman

    47
    0
    Dec 3, 2012


    Steve, the SCR diode finally arrived and has been replaced. When tested on a spare shorted 12 volt battery, the charger seemed to function just like the other working battery charger (it chargers until reaches 14.4 volts, then turns off until it falls to 13.88 volts, then restarts charging, and it loops this process continuosly). So at least it appears to be working now. :)
    Any luck deciphering the diagram?


    Woody

    Note: 2 amp setting is better for temporarily maintaining a battery once it starts maintenance cycle.
     
    Last edited: Jan 1, 2013
  19. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,448
    2,809
    Jan 21, 2010
    The circuit is sufficiently non-trivial that I need to spend some time looking at it :)

    Unfortunately work prior to Christmas was hectic and well, it's nearing the end of Christmas day now... Not an un-busy time of the year at home.

    I think that it's unlikely you could change this into a power supply without completely changing the circuit, battery chargers and power supplies are quite different beasts.

    The idea of the lamp in series with the battery is simply to limit the current to a safe value. At the voltages normally applied, you would never blow it.
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-