Simplest Charger/desulfator Ever


Introduction: Simplest Charger/desulfator Ever

This charger can charge almost any battery type at any voltage. It desulfates lead acid batteries as well. It works quite well. Be warned tho, it contains lethal voltages. If powered by 120vac it can get up to 170 volts and 340 volts on 220vac.

Step 1: Materials:

Ac run capacitor Rectifier or 4 diodes Switch(optional) Electrical cord

Step 2: Schematic

Step 3:

As you can see it is quite simple. The capacitor couples the battery to the mains as well as limiting the current. At 120vac it charges at 1 amp for ever 22uf in capacitance, 13 uf at 240. The switch is merely convenience so i dont have to unplug and replug. Then the diode bridge rectifies it to dc.

Step 4: Usage

it works in a way that if the battery is sulfated or weak etc. it will always charge at the preset amps. So if the battery is only taking 5 amps at 12 volts and u have it set for 10 amps, it will raise its voltage until it is charging at 10 amps. At 120vac the charging voltage could go up to 170vdc. 340 with 240. It also pulses at 120 herts which desulfates the lead acid batteries. It should also be noted that this is a universal charger and will charge any voltage battery. It should also be noted that the is no protection against over charging and if it is left on the charger when the battery is already charged it could damage the battery.



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    I built one of these. It really brings desulfated wheelchair batteries back from the dead.

    Capacity lead battery charger /desulfator can charge from 0v to full charge

    I've now rebuilt this desulfator with a switch that disconnects both the live and neutral mains lines and added a small PSU board from an old phone charger that runs an LED. I now plug this into a 24hr timer set to turn on for 30mins then off for 1 hour.

    I'm currently looking into adding a temperature activated switch that will sound an alarm and cut power to the desulfator side if the temp rises too much. I am however trying to keep it as simple as posible with as little cost and electronic assembly as possible.

    This thing dose it work and how long a charge do you nead to discharg recharg how many times if i dont get a reply i will asume the op has friyed hime shelf

    This circuit is LIVE and highly DANGEROUS !!

    Full mains voltage is available at the battery terminals unlike chargers that use a mains frequency or switch mode transformer..

    Contacting any of the wiring or connections with a grounded body (human or otherwise) could prove fatal.

    Maybe an experimental project for the lab.....But not where humans or animals could come in contact with it in any way..

    erm... another update. I... err... I may have killed the batteries, used them in an R/C car in parallel for more amps. Long story short, the rear drive of the R/C got bust/destroyed so the car in storage till i could rebuild. took it out today to check something out and, like a Doofenshmirtz, had forgot to disconnect the SLAs.

    Going to have to scrounge parts and rebuild defulfator (stripped it for another project) and a try a few other techniques first then this. fingers crossed.

    I love simple designs. However, I see some things I don't like:
    Protection: If the capacitor fails with a shortcut, -I don't even want to imagine that. A fuse it the minimum you should integrate.

    Ripple current of capacitor not regarded. Standard capacitors will can ripple currents about 2A. You want 5-10A. Make sure you don't cook the capacitor.

    Nobody guarantees that the battery is charged by nominal current! The current will be mainly determinded by battery resistance and resistance of the rest of the circuit.

    No overload protection. Yes it might remove reversable sulfatation, because this is usually done by applying overvoltage by a limited time. Overvoltage for a longer time will kill the battery quickly.

    1 reply

    This looks incredible! Definitely trying it out. Thanks!

    can i use it to charge a 48v sla battery pack of my ebike?

    1 reply

    Yes,12v,24v,36v,48v etc...

    Hi guys. I'm on 240V here and have cap from an old microwave (0.97uF, 2400VAC). Which rectifier or which diodes should I use? Thanks

    can't get hold of a starter cap however I do have a cap from a microwave. Would I be able to use this instead? We use 240v 60Hz mains which is also what the caps rated at?

    3 replies

    Gone ahead and created the circuit using the high-voltage microwave cap rated @ 0.72uF 2100v ac I have and a bridge rectifier from a dead PSU board and added a light so can see instantly if circuit is live.

    The results
    No bang!!! That's a first.

    2 x 12v 2.9Ah SLAs
    3hrs on charge : not charging.
    3hrs on this circuit : now charging.

    I'm now alternate the batteries 1hr on 1hr off.

    Oh and I never have more than one battery hooked up at anytime when charging or desulphating. I'm not that stupid lol

    A quick update. I still don't know the history of the 2 SLA's other than they were stone dead when salvaged from a bust electric recliner. However they are now back up and running thanks to this simple circuit.

    Still running strong even when they've been in heavy use and completely drained they've still recharged on a normal charger.

    Many thanks for your update I'll attempt to make this myself now

    I have questions about your success too. I made this charger long time ago, and I was experimenting only with one lead acid battery, 12V 55 Ah witch wasn't in use for long time, but I'm not sure that I improved it from sulfatization. However it was charging with this charger, my question is does it really work like desulfator?? I would like to read more comments of your expirience.

    op, are you still following this? I have questions about your success rate. I'm also concerned about that much voltage on a 12v. Did you track battery temperature? Did you ever put this on an oscilliscope? I wonder what %of a second there is voltage to battery. I suppose that is contingent upon capacitance. A small cap only sending voltage thru for a brief moment., etc.

    OP: What about when the battery voltage rises? The current through the capacitor decreases, so the charger would get slower and slower, the fuller the battery got.

    2 replies

    And I forgot to ask - what about the power dissipated in the capacitor? :)

    Well from what i can tell, i would be dissapating ~100 watts of power through the cap, but i never had any real heat or warmth com off it. Run capacitors are built for that. They have metal cases.