What fries an AC Adapter?

Discussion in 'The Projects Forum' started by Gdrumm, Jun 30, 2009.

  1. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    Last year, I had a battery charger for a power tool that got fried.
    Come to find out, there was a short in the battery, and it fried the AC Adapter. I went to Wal-Mart, and bought a better battery charger, one that wouldn't die when a battery shorts out. What is different between the cheap charger that comes with the power tool, etc., and the better charger that won't get toasted?

    Are there other things that can fry a charger / adapter?

    I now have another device, that did the same thing last night, I think.
    It is a portable Jump Start Battery / Compressed Air. I left it charging over night, and today, the charger is DEAD.

    Can I repair the charger?
    Can I repair the Jump Start device?

    Didn't see a similar post.

  2. SgtWookie


    Jul 17, 2007
    There's a lot of cheap stuff coming out of China nowadays. It's engineered for the lowest possible production cost, not for longevity.

    People are generally cost-conscious, and will likely buy the least expensive thing that they feel will suit their needs at the moment - but they'll expect that the less-expensive item will last at least as long as the more expensive item.

    Check your warranty on the items first. Best to get a brand-new one rather than try to fix something.

    As far as "what can fry stuff" - operating it outside of it's design parameters. A lightning storm nearby could cause that.

    Beyond that, you really haven't given us much information other than you have a couple of fried power accessories.

    We don't know the make or model of your items that no longer work. If they were made in China, the repair manual (if it exists) is probably written in Chinese.
  3. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    Sgt., thanks for the reply.
    I guess we can all relate to cheap.

    I thought perhaps the problem I refered to was a common one, enough so, that you guys on this formum would have figured out a work around.

    In laymans terms, would a shorted out battery cause such a problem?
    If so, what might I add to a circuit to circumvent the problem in the future?

    Could I build something that would protect future 110v AC adapters from getting fried, something external to the adapter itself, a filter, or circuit protector for the adapter itself, irregardless of the output voltage, etc.

    What does Black and Decker add to the high dollar adapter that protects it from such a demise as the cheap adapter? I'm thinking, both are probably made in China, but something is added to protect the more expensive one.

    Could that something be made as a stand alone item that any 110v adapter could be plugged into?

    Like a surge protector?

    I'm certain that both of my devices were not on a surge protector at the time they freid, but Black and Decker told me it was a dead battery that caused the Adapter to burn out, not a lightning strike.

    So, B&D know enough to safeguard the circuit, by adding something.
    I'm just wondering what is it they add, and can it be replicated and mass produced to go in every guys garage or charging station?

  4. NM2008

    Senior Member

    Feb 9, 2008
    AC Adapters dont like being shorted out,
    Why are your batteries shorting out all the time?
    Is the adpater suited to the batteries you are charging?
    Have you tried different batteries with similiar ratings?
    Regards NM
  5. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    It's not all the time.
    The first time it was something I had purchased and had used for years.
    The second time, it was a Garage Sale type item, a Jump Starter, which was probably in trouble before I bought it.

    When I talked with B&D about the first item, they implied that the shorting out is common problem, enough so, that they had developed and do sell a more expensive one.

    My question is, can I build something marketable to solve that problem?

    What's the difference between a cheap AC Adaptor, which is prone to shorting out, and the more expensive one, which is protected? Does anyone on the forum know?

  6. loosewire

    AAC Fanatic!

    Apr 25, 2008
    I sovled that promlem,I bought 3-a/c power drills. A 1/2 hammer drill
    3/8-1/4 with three plug adapter and heavy duty drop cord/with bits
    no more dead batteries. My son has power generator,so we trade off.
    Ready to go. The 1/4 inch for pilot holes to make life easier.Better than
    tearing your plaster up with shot tools. They steal battery power tools
    more than power tools,the pawn guy will only give them a buck for power
    drill. They don't realize that good ext-cord cost much more than tools.
    PackratKing likes this.
  7. someonesdad

    Senior Member

    Jul 7, 2009
    No circuit diagrams, so it's mostly speculation. But if it was me, I'd consider adding a fuse in series with the battery so that a short would blow the fuse. To protect the electronics, however, you might need a fast blow fuse; those can get pricey. A cheap resistor of the right value and wattage might be able to be used, but it would possibly cause the battery to not fully charge.

    It's likely the more expensive circuits involve something to control the maximum currents.
  8. tkng211

    Well-Known Member

    Jan 4, 2008
    There's a kind of passive component called PTC ( Possitive Temperature Coefficient) Resettable Fuse.
    Whenever there's a short or overloaded circuit, the fuse will cut off the power circuit. When the fault is cleared, it will reset itself to serve as a protective device. So replacement of fuse is not needed. You can google it. However, most of such fuses are rated with low working voltage and relatively smaller current, yet for those home appliance battery chargers, it shouldn't be any problem

    Last edited: Jul 9, 2009
  9. jj_alukkas

    Distinguished Member

    Jan 8, 2009
    You could build a simple ckt involving a relay and wiring it in series with the N\O terminals.. A micro switch serves as a power switch which is placed across the N\o and common.. a short would effectively cut the relay's power and so the whole power and only a manual switch on would help.. If the batteries are for 12v, you could use a single pole relay, if its for an odd voltage, you will need some regulation and a double pole one.. simple logics.. I once made such a device for my tv which would go and off if the line fails and comes suddenly..
  10. jj_alukkas

    Distinguished Member

    Jan 8, 2009
    Another way is monitoring voltage of the battery to drive a relay which controls the charger.. it involves some additional wiring..
  11. Gdrumm

    Thread Starter Distinguished Member

    Aug 29, 2008
    Can you explain the last reply in greater detail?
    As a first year electronics student, I'm not sure I could do it.

  12. jj_alukkas

    Distinguished Member

    Jan 8, 2009
    Ok, you can use this for safety of any linear 12v device, provided, the device works on 12V only and doesnt draw a heavy load.. Working is simple.. The switch completes the circuit and the relay latches.. It continues to be so until a short circuit occurs or power fails.. The simplest 12v circuit breaker.. It isn't a good circuit for digital circuits, but good for small batteries and even if it isn't useful, students starting in electronics can learn logics.. Use a different relay for that particular voltage..
    If your circuit draws heavy load, use a double pole relay .. The one shown here is single pole for easy understanding of working..


    The other method I stated is to monitor battery voltage.. If voltage goes too low, as if seen in a short circuit, the circuit cuts the relay. The difference between the above and this one is that the above one needs to be started each time and this one is automatic with the starting being in logics.. Hope this is digestable...