DIYbanter - View Single Post - little idea helped in electrolytic derusting problem

Grant Erwin

wrote:

On Oct 8, 11:23 pm, Grant Erwin wrote:

That got it down to about 16 amps, but the little charger is only a 10 amp
unit so after several minutes it popped again.

That's when I got my little idea!

I put a 20A variac in front of the battery charger and turned it down so the
charger only saw about 60% of its input voltage. Ah hah - can set the current
right on 10 amps! There were two drawbacks with using a $5 garage sale car
battery charger. One is that it won't deliver a whole bunch of current to do
e.g. a truck bed. The other is you only have one switch to control the current -
the 6V/12V toggle. Sure, you can monkey with your solution, or your topology,
but in this case monkeying with the topology would have meant starting over.

This is another handy use for the variac.

Grant Erwin
Kirkland, Washington

Another idea is to use a PC power supply. Look on Wikihow for more
info. I needed a 12 volt supply good for 12 amps and none of my old
supplies were rated that high. So I spent $2 at St. Vincent de Paul
and got a supply rated for 15 amps at 12 volts. For derusting you
might be able to use the 5 volt output ( 20 amps ) or the 3.3 volt
output ( 18 amps).

This took me 3 minutes! You want me to go buy something ELSE? Besides, I
wanted 10 amps at 6 volts .. my idea is to avoid replacing the supply.

Of course, you can build/buy another DC supply, Dan. You are entirely
correct as usual.

Grant