I don't know if this qualifies as cheap enough but one way is to use a
variable autotransformer, a transformer with a variable tap. With
120VAC in you can output from 0130 VAC.
Here is a link to a 10amp unit all cased up and ready to plug in. If you
are handy you can get the transformer itself for a lot less.
http://www.tenma.com/070.html
BTW, 9 amps seems kinda high, I would expect a 40amp charger to draw
about half that on the line side.
The other thing to keep in mind is that these use a wiper to vary the
tap, I have no idea how long that would last on a boat.
RB
..


Panama wrote:

I have a 40 amp battery charger that has a 5 position switch to select
the battery charging voltage. Works great. Allows steps from about
13.2 to 17 volts. Prob done by a multi-tap transformer?

Trouble is - AC voltages in Mexico can be as high as 128-130 VAC and
other places can be as low as 105 VAC. The charger reacts by changing
the battery charging voltage up or down - a little but enough to vary
the DC amps that get to the batteries. I'm not going to replace the
charger.

I'm looking for a cheap variac/scr/triac something gizmo that I can
wire into the AC line to the charger and make the effective voltage
(RMS value?) go up or down by +/- 10% or so. The AC in is about max 9
amps. It could even be a big wired wound variable resistor I suppose.
Then I can set the AC line voltage to what my genset puts out and use
the charger at it's max 40 amps all the time.

Any ideas or products. Preferably cheap and never needs replacement
like the 27 years old charger.

(No I'm really not going to replace the charger.)

Panama wrote:

.....Any ideas or products. Preferably cheap and never needs replacement

like the 27 years old charger.

(No I'm really not going to replace the charger.)

Is it less expensive to continually buy new batteries after your old cheap
battery charger fries them?

Priorities, man!

DSK

Panama wrote:

.....Any ideas or products. Preferably cheap and never needs replacement

like the 27 years old charger.

(No I'm really not going to replace the charger.)

Is it less expensive to continually buy new batteries after your old cheap
battery charger fries them?

Priorities, man!

DSK

Throw out that charger and get a good one. Those kinds of
variations in line voltage should not affect the output. I've
seen line voltages from 105 to 128 in our travels and the
battery charger always maintains the proper voltages and
currents. By the time you get a way to control the line
voltage you can by a new charger that works properly.

Doug
s/v Callista

"Panama" wrote in message
...
I have a 40 amp battery charger that has a 5 position switch to select
the battery charging voltage. Works great. Allows steps from about
13.2 to 17 volts. Prob done by a multi-tap transformer?

Trouble is - AC voltages in Mexico can be as high as 128-130 VAC and
other places can be as low as 105 VAC. The charger reacts by changing
the battery charging voltage up or down - a little but enough to vary
the DC amps that get to the batteries. I'm not going to replace the
charger.

I'm looking for a cheap variac/scr/triac something gizmo that I can
wire into the AC line to the charger and make the effective voltage
(RMS value?) go up or down by +/- 10% or so. The AC in is about max 9
amps. It could even be a big wired wound variable resistor I suppose.
Then I can set the AC line voltage to what my genset puts out and use
the charger at it's max 40 amps all the time.

Any ideas or products. Preferably cheap and never needs replacement
like the 27 years old charger.

(No I'm really not going to replace the charger.)

Throw out that charger and get a good one. Those kinds of
variations in line voltage should not affect the output. I've
seen line voltages from 105 to 128 in our travels and the
battery charger always maintains the proper voltages and
currents. By the time you get a way to control the line
voltage you can by a new charger that works properly.

Doug
s/v Callista

"Panama" wrote in message
...
I have a 40 amp battery charger that has a 5 position switch to select
the battery charging voltage. Works great. Allows steps from about
13.2 to 17 volts. Prob done by a multi-tap transformer?

Trouble is - AC voltages in Mexico can be as high as 128-130 VAC and
other places can be as low as 105 VAC. The charger reacts by changing
the battery charging voltage up or down - a little but enough to vary
the DC amps that get to the batteries. I'm not going to replace the
charger.

I'm looking for a cheap variac/scr/triac something gizmo that I can
wire into the AC line to the charger and make the effective voltage
(RMS value?) go up or down by +/- 10% or so. The AC in is about max 9
amps. It could even be a big wired wound variable resistor I suppose.
Then I can set the AC line voltage to what my genset puts out and use
the charger at it's max 40 amps all the time.

Any ideas or products. Preferably cheap and never needs replacement
like the 27 years old charger.

(No I'm really not going to replace the charger.)

Sounds like you need an "autotransformer".

Many Variacs are actually autotransformers, in that they accept 110V input,
and output from 0 to 130 volts AC. The principle works as such:

=======================
mmmmmmmmmmmmmmmm
| | ^
A B C

If you supply the inputs to wires A and B, and outputs on A and C, and C is
the adjustable portion of the Vairac. If the voltage from A - B is 110
Volts, when C is farther out on the transformer, you will see a higher
voltage from A - C (above 110 Volts). When it is inside of B you will
reduce the voltage (below 110 Volts).

My bench Variac actually inputs 110V, and outputs from 0 to 220V.

You can also do this with a multi-voltage transformer:

Do not care about Secondary
==========================
mmmmmmmmmmmmmmmmmm
| | | | |
A B C D E
100 110 120 130
This is a common multi-input voltage transformer used in international
equipment, having inputs of 100, 110, 120, 130 Volts. This will typically
be a low voltage transformer, but you really don't care about the secondary
side.

If you typically see from 100 to 130 volts and you want 110 volts, you would
hook up the output to A-C. and the input to:

100V A - B
110V A - C
120V A - D
130V A - E

With this setup, you will boost or decrease the voltage depending on where
you have the input.

You will need to find a transformer large enough to supply your peak
wattage, and remember that even if you normally draw 9A at 110V, in the 100
V boost configuration, your input current will be 9.9A.

Also autotransformers DO NOT isolate the secondary from the line, so
electrical shock is still possible.


"Panama" wrote in message
...
I have a 40 amp battery charger that has a 5 position switch to select
the battery charging voltage. Works great. Allows steps from about
13.2 to 17 volts. Prob done by a multi-tap transformer?

Trouble is - AC voltages in Mexico can be as high as 128-130 VAC and
other places can be as low as 105 VAC. The charger reacts by changing
the battery charging voltage up or down - a little but enough to vary
the DC amps that get to the batteries. I'm not going to replace the
charger.

I'm looking for a cheap variac/scr/triac something gizmo that I can
wire into the AC line to the charger and make the effective voltage
(RMS value?) go up or down by +/- 10% or so. The AC in is about max 9
amps. It could even be a big wired wound variable resistor I suppose.
Then I can set the AC line voltage to what my genset puts out and use
the charger at it's max 40 amps all the time.

Any ideas or products. Preferably cheap and never needs replacement
like the 27 years old charger.

(No I'm really not going to replace the charger.)

On Sun, 23 Nov 2003 16:43:03 -0800, Panama wrote:

I have a 40 amp battery charger that has a 5 position switch to select
the battery charging voltage. Works great. Allows steps from about
13.2 to 17 volts. Prob done by a multi-tap transformer?

Trouble is - AC voltages in Mexico can be as high as 128-130 VAC and
other places can be as low as 105 VAC. The charger reacts by changing
the battery charging voltage up or down - a little but enough to vary
the DC amps that get to the batteries. I'm not going to replace the
charger.

I'm looking for a cheap variac/scr/triac something gizmo that I can
wire into the AC line to the charger and make the effective voltage
(RMS value?) go up or down by +/- 10% or so. The AC in is about max 9
amps. It could even be a big wired wound variable resistor I suppose.
Then I can set the AC line voltage to what my genset puts out and use
the charger at it's max 40 amps all the time.

Any ideas or products. Preferably cheap and never needs replacement
like the 27 years old charger.

(No I'm really not going to replace the charger.)

Seems like I answered this in another newsgroup, but if you missed it...

There are two types of auto-regulating transformers. The old kind uses a
swinging core. As the voltage varies, the core moves in and out to provide
a more or less constant voltage. I say "more or less" as they can seldom
act fast enough to block transients, those very short term spikes which can
damage electronic gear.

The second type are called "ferro-resonant" transformers. They work by
driving the core into saturation and operate in parallel with a
non-polarized capacitor to ensure that the output voltage always remains
the same. They offer a few advantages, the best being that they do not
transfer voltage transients (spikes).

Both are rated in volt-amps and both are available on the surplus market.

Good luck
--

Larry
email is rapp at lmr dot com

Sounds like you need an "autotransformer".

Many Variacs are actually autotransformers, in that they accept 110V input,
and output from 0 to 130 volts AC. The principle works as such:

=======================
mmmmmmmmmmmmmmmm
| | ^
A B C

If you supply the inputs to wires A and B, and outputs on A and C, and C is
the adjustable portion of the Vairac. If the voltage from A - B is 110
Volts, when C is farther out on the transformer, you will see a higher
voltage from A - C (above 110 Volts). When it is inside of B you will
reduce the voltage (below 110 Volts).

My bench Variac actually inputs 110V, and outputs from 0 to 220V.

You can also do this with a multi-voltage transformer:

Do not care about Secondary
==========================
mmmmmmmmmmmmmmmmmm
| | | | |
A B C D E
100 110 120 130
This is a common multi-input voltage transformer used in international
equipment, having inputs of 100, 110, 120, 130 Volts. This will typically
be a low voltage transformer, but you really don't care about the secondary
side.

If you typically see from 100 to 130 volts and you want 110 volts, you would
hook up the output to A-C. and the input to:

100V A - B
110V A - C
120V A - D
130V A - E

With this setup, you will boost or decrease the voltage depending on where
you have the input.

You will need to find a transformer large enough to supply your peak
wattage, and remember that even if you normally draw 9A at 110V, in the 100
V boost configuration, your input current will be 9.9A.

Also autotransformers DO NOT isolate the secondary from the line, so
electrical shock is still possible.


"Panama" wrote in message
...
I have a 40 amp battery charger that has a 5 position switch to select
the battery charging voltage. Works great. Allows steps from about
13.2 to 17 volts. Prob done by a multi-tap transformer?

Trouble is - AC voltages in Mexico can be as high as 128-130 VAC and
other places can be as low as 105 VAC. The charger reacts by changing
the battery charging voltage up or down - a little but enough to vary
the DC amps that get to the batteries. I'm not going to replace the
charger.

I'm looking for a cheap variac/scr/triac something gizmo that I can
wire into the AC line to the charger and make the effective voltage
(RMS value?) go up or down by +/- 10% or so. The AC in is about max 9
amps. It could even be a big wired wound variable resistor I suppose.
Then I can set the AC line voltage to what my genset puts out and use
the charger at it's max 40 amps all the time.

Any ideas or products. Preferably cheap and never needs replacement
like the 27 years old charger.

(No I'm really not going to replace the charger.)

On Sun, 23 Nov 2003 16:43:03 -0800, Panama wrote:

I have a 40 amp battery charger that has a 5 position switch to select
the battery charging voltage. Works great. Allows steps from about
13.2 to 17 volts. Prob done by a multi-tap transformer?

Trouble is - AC voltages in Mexico can be as high as 128-130 VAC and
other places can be as low as 105 VAC. The charger reacts by changing
the battery charging voltage up or down - a little but enough to vary
the DC amps that get to the batteries. I'm not going to replace the
charger.

I'm looking for a cheap variac/scr/triac something gizmo that I can
wire into the AC line to the charger and make the effective voltage
(RMS value?) go up or down by +/- 10% or so. The AC in is about max 9
amps. It could even be a big wired wound variable resistor I suppose.
Then I can set the AC line voltage to what my genset puts out and use
the charger at it's max 40 amps all the time.

Any ideas or products. Preferably cheap and never needs replacement
like the 27 years old charger.

(No I'm really not going to replace the charger.)

Seems like I answered this in another newsgroup, but if you missed it...

There are two types of auto-regulating transformers. The old kind uses a
swinging core. As the voltage varies, the core moves in and out to provide
a more or less constant voltage. I say "more or less" as they can seldom
act fast enough to block transients, those very short term spikes which can
damage electronic gear.

The second type are called "ferro-resonant" transformers. They work by
driving the core into saturation and operate in parallel with a
non-polarized capacitor to ensure that the output voltage always remains
the same. They offer a few advantages, the best being that they do not
transfer voltage transients (spikes).

Both are rated in volt-amps and both are available on the surplus market.

Good luck
--

Larry
email is rapp at lmr dot com

Panama wrote:

I have a 40 amp battery charger that has a 5 position switch to select
the battery charging voltage. Works great. Allows steps from about
13.2 to 17 volts. Prob done by a multi-tap transformer?

Trouble is - AC voltages in Mexico can be as high as 128-130 VAC and
other places can be as low as 105 VAC. The charger reacts by changing
the battery charging voltage up or down - a little but enough to vary
the DC amps that get to the batteries. I'm not going to replace the
charger.

I'm looking for a cheap variac/scr/triac something gizmo that I can
wire into the AC line to the charger and make the effective voltage
(RMS value?) go up or down by +/- 10% or so. The AC in is about max 9
amps. It could even be a big wired wound variable resistor I suppose.
Then I can set the AC line voltage to what my genset puts out and use
the charger at it's max 40 amps all the time.

Any ideas or products. Preferably cheap and never needs replacement
like the 27 years old charger.

(No I'm really not going to replace the charger.)

The specified/allowed 'Voltage variation' plus/minus varies (pun
intended!) a little from country to country and region to region.
E.g. North America, Europe, etc.
In some places it may be plus and minus ten (10) per cent. In
another area it may be, say, minus 6% to plus 10%. If in Mexico
the voltage is occasionally up to 128/130 on a supply that is
supposed to be 117/120 volts; that's around 9% to 11% high. i.e.
acceptable? If you are monitoring it anyway why worry? Is in
danger of burning out. i so tap it down to the next lower
ampere/voltage output setting?
Or am I missing something?