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  1. I had to read that a couple of times before I realized you probably meant “desulfator”. “Desolator” sounds pretty cool too, though – like one of the more badass Decepticons.

  2. ironleg says:

    Having a little more detail about how to determine rate of success in this, the amp-hour rating of “revived” batteries, and a disclaimer that even with desulfation there’s going to be a lot of batteries which won’t come back with enough capacity to be worth the bother would be good.

    I worked with these lead-acid batteries for years and have tried similar methods of reviving them in my spare time. Getting a dead SLA to read 12v is entirely different than getting it to be able to hold up a decent load over a decent amount of time.

  3. John S says:

    Mikey’s charger/desulphator (mine was a kit) is the dog’s bollocks. The tolerances on the plexiglass safety shield were a bit tight and the shield is prone to cracking if the mounting bolts are over-tightened.

    Overall it works like a charm. Small, compact, beautiful. If you build or buy one of these and do your first charge, make sure the charging leads are hooked to the battery and that the small metal LED meter switch is in the OFF position. Now plug the unit into your wall socket, wait a few seconds.

    Now you can flick the little metal switch to ON to see the charging volts. If you don’t hook things up in that order, chances are that R1, a 10k resistor, will cook due to the surge voltage.

    A little more detail on how this unit achieves useful desulphation would be appreciated.

  4. OrkneyOctopus says:

    s/desolator/desulfator/

  5. SuperUnknown says:

    Mikey’s DaPimp works great! It recovered a couple of 18V Dewalt NiCads and a *BIG* 8D (60kg!!) Caterpillar battery. I only wish it had a built in timer…

    But he’s got great service and answers questions in a flash!

  6. Dax says:

    Remember that the DaPimp offers no isolation from mains, so it’s actually very dangerous to use. If the battery leads should come disconnected, or if the battery has an internal break, you get high voltage with enough amperage to kill on the wires and the device may catch fire because the voltage is fed back through a pair of low wattage resistors that will start to overheat.

    Following the circuit diagram, the device basically takes raw mains power, limits the maximum current with a bunch of capacitors that act as impendance to the AC (they don’t contribute to any sort of high-current pulse), and then puts the AC through a diode bridge to get pulsating DC current out. The less current the battery draws, the higher the circuit lets the voltage rise which makes the circuit draw more current and operate like a rudimentary constant-current source, forcing about 1 amps through the battery whether it wants it or not.

    The rest of the circuit simply implements a voltage meter.

    The pulsating DC doesn’t really work as advertised. Generally speaking, the sulfate deposits formed on the battery electrodes need a higher than normal voltage to dissolve back, and the capacitive coupling allows the charging voltage to rise to accomplish this, but as small spots of sulfation are removed, the battery’s internal resistance drops and so the charging voltage drops. So this device won’t exactly revive your battery to full health, but it’s better than nothing.

    Proper desulfators use very fast very high current pulses to drive the voltage at the plates up and break down the deposits while keeping the average charging current low so the battery won’t boil over or develop hydrogen bubbles.

    Using it on NiCad is inadvisable because NiCad batteries behave opposite to lead acid – they develop metal whiskers that decrease the internal resistance by shorting the electrode material, so the device doesn’t really do anything for NiCads, except perhaps overcharge and overheat them. For smaller NiCad batteries, the forced current may burn some of the whiskers away to allow the battery to operate again, but the heat will damage the battery otherwise.

    NiMH batteries have no known mechanism to revive so the device is useless for that, and using it on lithium batteries is a receipe for disaster because lithium batteries are very sensitive to overvoltage and can burst into flame if so treated.

    1. Dax says:

      Also, one of the battery terminals will always carry mains voltage when the device is operating. Depending on which way tha AC plug is in, you get either a 1.5 Amp fuse and a diode, or a capacitor and a diode between you and the grid if you touch the wrong terminal. The capacitor or the fuse will not limit the current enough, nor will they protect you because the body won’t pass enough current to burn the fuse.

      That’s why TOUCHING THE BATTERY TERMINALS IS DEADLY.

      I’m a little surprised that they still allow this device to be sold.