How to revatilize (charge) a new but dead battery?

Discussion in 'General Electronics Chat' started by pintree3, Oct 30, 2014.

  1. pintree3

    Thread Starter New Member

    Oct 30, 2014
    3
    0
    I bought a Dirt Devil Scorpion that just won't charge. It goes past its 24 hours charging time and the light remains red, as if still charging, and even if left longer the power won't last more than 4 minutes. Dirt Devil is replacing it so no problem and this one should be thrown away but then I thought is it possible to make this battery come to life? Under its specs it says: Nickel cadmium 6V 6 amps.
    On thing I tried is while charging I removed it from the charger for about 2 minutes then set it on/off/on/off real quick about 6X (having seen this elsewhere for old used batteries) but nothing happened.
    Any advice would be appreciated--though as one video suggested, hooking it up to 2 other equal batteries is not the thing I was looking for as an answer.
    Regardless, as mentioned, all help would be appreciated.
    Or could the charger actually be the problem?
    Thanks
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
  3. takao21203

    Distinguished Member

    Apr 28, 2012
    3,577
    463
    A NiCAD / NiMH which only keeps charge for a few minutes usually has a leak, and isnt recoverable.
     
  4. Dr.killjoy

    Well-Known Member

    Apr 28, 2013
    1,190
    156
    It most likely has a couple dead cell that can be replaced if the battery case comes apart in one piece ..
    I know Nicads have a memory and Some times you have to drain the cell to next to no voltage in order to clear the memory...
     
  5. pintree3

    Thread Starter New Member

    Oct 30, 2014
    3
    0
    I thank you all :)
    bertus. It seems that this choice, using a reflex charger, is something I would have to build myself which is not something I am fully capable of. I did a search on eBay, Amazon and Google to see if I can buy such a unit (universal and not specific) and could not find it.
    Takao20203 If it does have a leak then there is no way of me knowing. Or is there a way?
    Dr.killjoy, if some of the cells are dead then it would be nice to know how I can find this out.
    Finally, in doing some reading I read that the more you charge and recharge new Nicads the better it is--they are not at their full potential when they are new. So perhaps charging/recharging many times can help it (though with such a slow start this may not improve by much.
     
  6. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    You can cobble together a quick & dirty pulse charger, Open frame SMPSU cards used to be plentiful from salvage/surplus dealers - rig a charge pump voltage doubler by connecting a capacitor to the pulse side (anode) of the 12V rectifier, the other end of the capacitor is shunted by a power Shottky-barrier rectifier which allows the + excursions to pass. The clever bit is using a standard fast silicon rectifier to pass the + peaks to the battery. The SB rectifier is very fast and its lower Vf minimises negative excursions - the fast silicon rectifier has significant Trr and feeds sharp discharge spikes to the battery.

    The regulation is usually on the +5V rail - you have to load it to keep the SMPSU pumping.
     
  7. pintree3

    Thread Starter New Member

    Oct 30, 2014
    3
    0
    Thanks ian field but what you mention is beyond my capability and comprehension. As much as electronics interest me, and they do, I am not an electrician. I don't even own a voltage meter but I am in process of buying one. ( I do own a battery tester though :). Having said this, if it's simple enough (I am no dummy after all), I am willing to try things out.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
    4,415
    784
    My simpler version pulse charger was published in a July/August summer issue of Elektor magazine.

    Truth be told, its actually slightly more complicated - a network of diodes is needed to isolate mains zero-crossing points to generate the pulses, and to prevent MOSFET burnout/battery discharging if the mains fails. But it runs from a regular mains frequency step-down transformer (or an AC output plugpack), so little or no exposure to live circuits.
     
  9. WBahn

    Moderator

    Mar 31, 2012
    17,777
    4,804
    If you charge the battery and let it sit overnight is it dead again, or do you still get a few minutes use out of it the next day just as though it had just come off the charger?
     
Loading...