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HELP With Step-Down Transformer and Converter

T

The Phantom

Jan 1, 1970
0
Dear Phantom,
I have broken-down what I need as follows:
A. 2 Volt Lead Acid Gel Cells, RAted 25 ampere-hours (6 pcs)
B. 12 Volt Cylindrical Battery (1 pc), looks like a big AAA Batery
right?

No.

The 12 volt battery I was referring to is *made* of 6 pcs of 2 volt cylindrical lead
acid gel cells. I think it may be easier to find a 12 volt battery of 6 cells than to
find the individual 2 volt cells.
C. Ammeter, DC responding (1 pc)

If you use a shunt + millivoltmeter, then for the AC setup the millivoltmeter must be AC
responding; for the DC setup the millivoltmeter would have to be DC responding. This
millivoltmeter could be a hand-held DVM, such as a "Fluke" meter.

If you want a self-contained ammeter (no shunt, in other words), it would be the
clamp-on type, and those are pretty much all AC responding.
D. Switch for the safety disconnect

This would be for the AC setup (on the primary of the transformer); for the DC setup the
breaker(s) will also serve as the safety disconnect.
E. 5000 amp shunt (1 pc)

This would be for the AC (3000 amp) setup. For the DC setup, you might want a 1000 amp
shunt. If you can live with the reduced resolution, you *could* use a 5000 amp shunt in
your DC setup; just switch the millivoltmeter from AC responding to DC responding.
F. millivoltmeter

This could be a hand-held DVM, such as those made by Fluke, or any other similar unit.
F. Circuit Breaker 12 Volt DC-Rated, 750 Amp (1 pc)

Or three 250 amp breakers in parallel, or some other combination that adds up to 750
amps (all the same, of course), if you can't find a 750 amp breaker.
G. 12 Volt Charger (AC to DC)

Series Connection When Charging:
AC Outlet >>>>> Charger >>>>> +Battery #1- >>>>> +Battery#2+

The individual 2 volt units are properly referred to as "cells"; when you connect a
number of them together, you have a battery (of cells). The 12 volt battery is properly
referred to as a battery of 2 volt cells, so the connection is AC outlet>>>>charger>>>Cell
#1>>>Cell #2>>>etc.>>>Cell #6. If you got the cells already wired up as a 12 volt
battery, you just rewire it that way to charge.
Parallel Connection when Generating High Current
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
| | | | | | |
Battery#1 Battery#2 Battery#3.....Battery#6 Cir.Breaker====| Ammeter
|_ _ _ _ _ |_ _ _ _ _|_ _ _ _ _ _ _ _|_ _ _ __| |_ _ _|

1. Where do I put the Switch, Shunt and Millivoltmeter in the diagram
above?

The breaker *is* the switch. The shunt is in series after the breaker and the
millivoltmeter is connected to the small screws on each side of the shunt--the meter
connection points. Like this:

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _Cir.Breaker_ _Shunt_ _
| | | | |
Cell#1 Cell#2 Cell#3..........Cell#6 |
|_ _ _ _ _ |_ _ _ _ _|_ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _|

The piece of wire that conpletes the connection from the right side of the shunt and
comes back to the bottom connection to the 6 cells is what determines how much current
there will be. That's the piece that I said should be about 8 feet of 2/0 (that's
pronounced "two aught") cable.
2. Do you mean that I should dissect the 12 Volt Cylindrical battery
and use the wires inside it as connectors to the Lead Acid Batteries?

If you get a 12 volt battery made of Gates cylindrical cells, the "wires" that connect
the cells together will be straps of plated copper. They will be very easy to get at. If
you get a 12 volt battery with a "rectangular" shape, the individual cells will not be
accessible without destroying the battery. The individual Gates cells are readily visible
and accessible in the type of battery I'm recommending. To wire th cells in parallel you
need to use very heavy copper conductors. You could get copper tubing at the hardware
store, say 3/8" and cut off appropriate lengths, flatten the ends with a hammer and drill
holes to connect to the cells.
3. Although I can get very high current in the above setup, my voltage
would exceed the 0.90v to 1.50v range that I wanted, isn't it?
Basically, high current is generated by shorting the battery, is this
right?

Right. But the 2 volt cell voltage will drop when they are shorted. I don't know
exactly how much, but the voltage will drop more or less linearly along the length of the
cable. For some length the voltage drop will be .9 to 1.5 volts.
4. If I decide to have a high DC Current and still maintain the DC
Volts at 0.90v to 1.50v range (to test faraday's induction law), I can
still use the design for the primary and secondary coil you provided,
right? Then I would need an interruptor to induce high current, right?
What should I use for an interruptor or where can I buy one? Is it
the same as pulsed DC?

Well, it would be pulsed DC all right!
I tried using a 12Volt Cylindrical BAttery some time ago and had a
smaller model with a thin Primary and a thick Secondary but I was not
able to induce a higher current in the secondary. My research tells me
that what I need is an interruptor that will correctly turn the primary
circuit ON/OFF at precise time. I used an ordinary ON/OFF switch as my
interruptor but nothing happens.

I'm going to try to email you. If the email address in the header isn't going to reach
you, can you post one that works? You could always go get a throw-away hot mail or yahoo
account for this purpose. If you post a real email address that you don't want to get
spammed, don't forget to disguise it, say with alternate spaces between letters or some
such.
 
M

Mike

Jan 1, 1970
0
gene said:
Parallel Connection when Generating High Current
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
| | | | | | |
Battery#1 Battery#2 Battery#3.....Battery#6 Cir.Breaker====| Ammeter
|_ _ _ _ _ |_ _ _ _ _|_ _ _ _ _ _ _ _|_ _ _ __| |_ _ _|

Note that in this picture, the circuit breaker is not fully protecting
your circuit. If a short develops in any of the battery wiring on the
left, there will be much fire and sparks. The circuit breaker won't notice.

This is aside from the slightly dubious practice of paralleling cells. What
happens if one cell shorts? A: More fire and sparks.

Is it possible to use a single larger battery or cell, rather than doing the
above?
 
T

The Phantom

Jan 1, 1970
0
Note that in this picture, the circuit breaker is not fully protecting
your circuit. If a short develops in any of the battery wiring on the
left, there will be much fire and sparks. The circuit breaker won't notice.

This same thing is true of a 12 volt battery of Gates cells as purchased (sometimes they
come with a plastic cover to protect the strapping from accidental contact). As I
remarked to the OP, if you're working on your car and drop a wrench across the battery
terminals, fireworks result. It's not possible to have absolute protection from every
possible mishap.
This is aside from the slightly dubious practice of paralleling cells.

It's the optimum thing for what the OP wants to do, cost wise and hassle wise. It will
be for a short term experiment, and since it's only slightly dubious, no problem.
What
happens if one cell shorts? A: More fire and sparks.

What happens in a big 2 volt golf cart cell if a short occurs between a pair of opposite
plates? The rest of the plates in the cell drive a large current through the short. How
shall we protect against this? If a cell shorts internally, it will probably be through a
separator, and the short will blow out, without fire and sparks.
Is it possible to use a single larger battery or cell, rather than doing the
above?

Then, as I implied, he would have to have a charger suitable to charge a single 2 volt
lead-acid cell. And such a cell would cost a lot more, expecially if he can find a Gates
battery surplus. The telephone companies regularly sell off those batteries; they use
them in the central offices for a few years, then dump them. They've usually got a lot of
life left.
 
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