Bad Boy Charger

This is one of those hacks that scares me a little bit. The ‘Bad Boy’ charger was created by Tom Martin to charge EV battery packs. [Pictured is one built by Mike Chancy] You can find the schematic under austinev’s tech files. This thing is a bare minimum power supply – it’ll deliver loads of essentially unregulated power into a set of batteries. If you check out the circuit, you’ll see just how scary this thing really is, but according to its users, it works.

21 thoughts on “Bad Boy Charger

  1. wow, bare bones power supply. That’ll produce quite a current on the DC Side of the charger, I can imagine that it is rather effective (don’t know the requirements for these EV Batteries) but would require constant supervision while in use. Not planning on building one of these, I’ll stick with my 40 dollar 15amp powersupply from rat shack, granted it can’t charge a 152v battery cluster but… I’m not powering anything that intensive!

  2. Gosh! that’s scary!! With all due respect, you don’t know much about how a dimmer work and its limitations. Dimmers are not designed to manage inductive loads, humming badly and producing horrible results, including overheating of it. In addition, the circuit doesn’t even has a protective fuse!!! Buddy, don’t recommend these type of circuits to others and make sure that your house insurance is up to date!!

  3. It’s fine if you want a backup so you won’t be off the road, but use it regularly and it’s easy to kill a $2k pack. Spend your money on a good charger, then buy batteries with what’s left over.

  4. Holy Zombie Jesus!

    That’s not actually DC coming out of the bridge… mind you, it has a DC offset and no reverse current .. but still … put some bulk caps and smooth that sucker out!

    I wonder what effect the AC components of the signal has on the batteries…

  5. RE: pulsing current

    Generaly a good idea for nicads, NiMH, and lead-acid. On the first two it blows out “crystals” or something that forms on the plates, shorting the battery out. In lead-acid cells, the pulsing fights sulfation.

    In fact there are devices that draw off current from the battery, and then recycle that power into a charging pulse. It still slowly discharges the battery, but it uses some of the juice to fight sulfation buildup, keeping the battery useful.

  6. Admittedly the circuit is pretty damn scary… But when you consider that they are hooking it up to a battery bank capable of sourcing thousands of amps and >100v that is really scary.

    But even more scary is that the person who built it not only got shocked several times (that should not happen regardless of how shaky a circuit is, you should ALWAYS turn it off when you are fiddling with anything with >40v in it) but that he managed to melt a dimmer… Ever heard of a variac, or at least a fuse?

    No offense Tom, but serously x_X

    In any case, I am impressed by your ingenuity, but I can’t quite figure out why you did not just run the dimmer into a 1:1 isolation transformer with a bridge rectifier on it…

    Unless that transformer is like 2:1 or something (thus allowing you to double the max current you can pull for a rated dimmer while compressing your range from 1-160v to 80-160v) I don’t see the point for that incredibly scary circuit…

  7. vell zif uoo look ez little closuer you will see zat zee transformer outpoot is wired in reverze… so zee powver through zee dimmer vill cancel zee powver though zee secondry. no dimming, no powver flow… a little diming of zee primary and a little powver vill flow. iz a little mure complex zan it loogz. no???

  8. People keep posting “scary”, but they’re not really saying why. This setup is abusive to nearly every component in the circuit.

    1) The transformer isn’t fused.
    2) Inductive loads will kill a light dimmer.
    3) God knows what the load on the transformer secondary is.

    But, most importantly:

    4) Dumping unregulated current into lead-acid batterys can cause them to emit flamable hydrogen, as a best case, and cause a deadly explosion (of acid and lead!) as a worst case. Nobody should use this ridiculous technique. It’s like plugging high wattage speakers into wall current- yeah, it’ll make a really loud 60 hz tone, but it’s way-stupid.

  9. Bad Design, but a few good ideas

    Bad Part – Dimmer – Most dimmers are for resistive loads, not inductive, that’s why he kept blowing them up.

    How it works, there is no details on the transformer, but if correctly wired, it will increase the output voltage.

    E.G. if input was 120v and output was 40v, wired 1 way you would get 160v (if phases are correct), and the other 80v (if phases are incorrect)

    as the battery packs are >120V, you have to step the mains up to be able to charge them.

    The supply is unregulated, some batteries prefer this as the stops the build up of problems in the cells

    Early car battery chargers were just a sutable transformer and a bridge rectifier, and as long as it was the correct transformer, the output was ok for a car battery, as the battery started to fill, the voltage difference between the charger and battery drop, current drops, and once the Battery is the same voltage as the charger – it stops.

    Nice Ideas, but I would exspect a better design for an expensive battery for you electric car.

  10. A better idea for controlling the current; Use a filament transformer, say 120v to.. maybe 12v, as some current, maybe 10A or better, hook a large reostat ( LARGE power adjstable resistor ) across the low voltage side, and use the PRIMARY of the transformer IN SERIES with the load you want to control.
    Ovbiously you want to play with values to figure out what the optomium values are for whatever you want to control, OR what you can get out of what you have on hand.


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