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Thread: Battery Charger Dead - does 6v 12v and 24v

  1. #21
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    I can understand you abandoning this job and it's a tempting offer as I have replacements for some key components on hand here like the mosfet in particular.
    It's just an issue of time and do I need another battery charger if the repair succeeds (already have trouble getting into the shed



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    wise choice gt250 could almost be sure the osc had failed so when you power it up its shortcircuit current goes bang and takes out allsorts and turns it into liquorice lol cheers don

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    Charger to be posted off...

    Once again, my sincere thankyou's to all the people who chipped in to help.

    Cheers,
    GT250

  • #24
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    Update:
    Received the patient today (Thanks to GT250 )
    Checked everything out on the HV side & no other faults found
    Replaced the FET and 0.22 ohm resistor (temporary for testing purposes) and all appears good again - front panel lights up and selection buttons working fine
    So it seems the initial fault was the FET failing which blew the fuse and potentially damaging R11 (0.22). Repairing the fuse and firing it up a second time with the faulted FET still connected finished off R11.

    Re-assembly will take a while as I only had a 5W resistor which is too large to fit in safely so now waiting for a resistor of the correct form factor and a pigtail fuse, maybe a beefier FET (higher Id + lower Rds) as well.

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    Glad to see you have got it all working Skepticist.

    Would have been a shame for me to have thrown it away - or killed myself
    I just got off continuing by the 'what if, this is wrong after you replace this and that stuff'. Which is all very valid I might add. You had the skill to test the HV side, which I did not.

    Well done.

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  • #26
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    Fully functional now (as far as I can tell anyway)
    Has a tougher FET now and improved the heatsinking with a bit of thermal paste



    Will give it a workout on a couple of car batteries I've been de-sulphating for a while

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  • #27
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    Definitely spoke a little too soon on this one as it was going through the motions OK like detecting the battery, state of charge, voltage etc but nothing was happening at the output when charge 'start' was selected. Dug a bit deeper and it turns out nomeat nailed it earlier
    IE removed the PWM controller card and the chip has a crater in it near the output pin so it's very dead



    That's greatly magnified, the chip is SOIC about 5mm square
    Must consider whether to pursue this further now, the chip being cheap and very available

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  • #28
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    Quote Originally Posted by Skepticist View Post
    Definitely spoke a little too soon on this one ......................................... removed the PWM controller card and the chip has a crater in it near the output pin so it's very dead
    bluddy good thing you weren't charging someone to fix this.
    I'm out of my mind, but feel free to leave a message...

  • #29
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    Can't put a price on fun

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  • #30
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    Quote Originally Posted by Skepticist View Post
    Definitely spoke a little too soon on this one as it was going through the motions OK like detecting the battery, state of charge, voltage etc but nothing was happening at the output when charge 'start' was selected. Dug a bit deeper and it turns out nomeat nailed it earlier
    IE removed the PWM controller card and the chip has a crater in it near the output pin so it's very dead



    That's greatly magnified, the chip is SOIC about 5mm square
    Must consider whether to pursue this further now, the chip being cheap and very available
    THAT'S NOT FUN...

    THIS IS FUN:




    After frying 3 sets of IGBTs, rebuilding the controller board, redesigning the PCB so there can actually be some fuse protection... I am having a little break.


    Sorry for the lo-res img. Postimages.org now suck, as they think this image violates their T&Cs.
    Last edited by Uncle Fester; 28-03-19 at 10:19 PM.
    Update: A deletion of features that work well and ain't broke but are deemed outdated in order to add things that are up to date and broken.
    Compatibility: A word soon to be deleted from our dictionaries as it is outdated.
    Humans: Entities that are not only outdated but broken... AI-self-learning-update-error...terminate...terminate...

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  • #31
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    In for a penny, in for a pound (must be old age )
    Found 3 faults on the PWM board IE UC3845 chip, 1N4148 shorted and a 1k resistor open cct so not giving up just yet and should have a replacement chip in a week or so.

    PWM board waiting for new chip, D3 & R12 already replaced

    Last edited by Skepticist; 30-03-19 at 10:21 AM.

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  • #32
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    Success at last - charged a battery with it after fitting in a new PWM controller chip (UC3845)
    It did inexplicably blow the fuse early in the testing procedure but no other damage found so I put it down to the fast fuse I used plus a spike in demand and plan to make it a slow blow type before reassembling the case.
    It's possible that the NTC thermistor isn't working as well as intended although it appears OK after a once over - better put it through its paces just to be sure.



    Yep - thermistor is bad - stuck at about 3 ohms at ambient temp when it should be more like 25 ohms at 25C so now waiting for another postal delivery (getting used to it by now)
    Last edited by Skepticist; 06-04-19 at 09:26 PM.

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  • #33
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    I think we are all waiting for you to bring it back working fine Skepticist

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  • #34
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    Finally fixed and passed multiple tests today.
    End result about $20 parts, $1000+ labour lol but as a one-off educational thing that's acceptable.
    If there was a dozen of them broken down they'd be cannibalised and the remains sent to landfill very quickly.

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