# [EVDL] bad boy charger with a variac



## EVDL List (Jul 27, 2007)

I've used a bad boy charger all last year with my 120
volt system.

Now I'm working a 72 volt bank.

So coming into the AC outlet:

1- on the black wire a transformer that has been
rewired with taps.

2- then both the black and white would go into this
huge variac transformer.

3- then that output would go into a bridge.

4- perhaps put a 5uF cap in series.

---------------------------
Do I have the tapped transformer in the right spot?

I would dial the variac to the correct voltage,
without the batteries connected, and mark those spots.


thanks

Michael Golub

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## EVDL List (Jul 27, 2007)

> mike golub wrote:
> > I've used a bad boy charger with my 120 volt system. Now I'm working
> > on a 72 volt bank...
> >
> ...


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## EVDL List (Jul 27, 2007)

Yes that tapped transformer would act as "bonn"
inductor. I'll make it out of an old microwave
transformer. I cut out all the old wires, and then add
new ones. Last time I use 12 gauge, but I guess I can
use smaller wire, because the "E" and "I" plates
absorb the current?

But was I correct that this inductor should go before
the variac, on the black 120vac wire?


You might be suggesting that the tapped transformer is
not
being used as 
a transformer, but rather as a tapped series inductor.
It
has much the 
same purpose as the series capacitor -- it acts as a
lossless dropping 
"resistor" to limit the peak charging current or
voltage.


> --- Lee Hart <[email protected]> wrote:
> 
> > mike golub wrote:
> > > I've used a bad boy charger with my 120 volt
> ...


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## EVDL List (Jul 27, 2007)

I've been using a bridge & variac for years as a charger. Is there any
problem with ripple? Do I really need to put a capacitor in to smooth it
out? Lawrence Rhodes....

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## EVDL List (Jul 27, 2007)

> mike golub wrote:
> > Yes that tapped transformer would act as "bonn"
> > inductor. I'll make it out of an old microwave
> > transformer. I cut out all the old wires, and then add
> ...


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