"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.

I would not really worry about the voltage out as long as it is greater then
13.7vDC it should charge the batteries fine. You should be able to pick up
a used variac off ebay or get one new from fisher scientific. They
generally will supply from 0% to 120% of the input voltage. You should wire
a volt meter into the variac to see your output voltage before you plug the
charger into it. We use tons of them to regulate our furnaces at school so
they are straight forward to wire just keep in mind they supply a % of the
input voltage. So if you are overdriving the output and the input ramps up,
the output side may be more voltage then what the charger can tolerate.

good luck,
mark

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.)

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

I also have used the regulating transformers at large commercial on shore
radio/computer installations. Sola was the brand we used, one on each leg of
3 phase shore power. Some critical units had small single phase
transformers mounted in the rack. They covered about 95-135 volts in for
constant output. However, they take several cycles of power change for the
change to be seen at the output. I got into trouble having a large UPS unit
feeding the transformers, as the transformer change was slower than the UPS
and we got into a voltage bucking problem. Ended up taking the transformers
out and just using the UPS. Do a web search for Sola line regulator
transformers (they are really a mag amp autotransformer device). E-bay has
them from time to time.

Doug K7ABX

"Leanne" wrote in message
...
In one radio station in which I worked, they had some regulating
transformers
that
would give 118 vac out with 95-135 volts in. There were taps to run it off
220,
which
they did, with an input of + or - 20 volts for 230 out. There was one
thing that
should
be noted is that they get very warm if running near the rated load. They
also
used to
hum a bit.

Leanne

I also have used the regulating transformers at large commercial on shore
radio/computer installations. Sola was the brand we used, one on each leg of
3 phase shore power. Some critical units had small single phase
transformers mounted in the rack. They covered about 95-135 volts in for
constant output. However, they take several cycles of power change for the
change to be seen at the output. I got into trouble having a large UPS unit
feeding the transformers, as the transformer change was slower than the UPS
and we got into a voltage bucking problem. Ended up taking the transformers
out and just using the UPS. Do a web search for Sola line regulator
transformers (they are really a mag amp autotransformer device). E-bay has
them from time to time.

Doug K7ABX

"Leanne" wrote in message
...
In one radio station in which I worked, they had some regulating
transformers
that
would give 118 vac out with 95-135 volts in. There were taps to run it off
220,
which
they did, with an input of + or - 20 volts for 230 out. There was one
thing that
should
be noted is that they get very warm if running near the rated load. They
also
used to
hum a bit.

Leanne

On Tue, 25 Nov 2003 22:14:36 GMT, "Doug K7ABX"
wrote (with possible editing):

I also have used the regulating transformers at large commercial on shore
radio/computer installations. Sola was the brand we used, one on each leg of
3 phase shore power. Some critical units had small single phase
transformers mounted in the rack. They covered about 95-135 volts in for
constant output. However, they take several cycles of power change for the
change to be seen at the output. I got into trouble having a large UPS unit
feeding the transformers, as the transformer change was slower than the UPS
and we got into a voltage bucking problem. Ended up taking the transformers
out and just using the UPS. Do a web search for Sola line regulator
transformers (they are really a mag amp autotransformer device). E-bay has
them from time to time.

Doug K7ABX

I think there are two kinds. One type uses a swinging core in the
transformer and works by adjusting the output voltage. The other uses
what is known as a "ferroresonant" transformer which works by
saturating the core at resonance with a non-polarized capacitor which
keeps the output steady regardless of input voltage swings. In a
marine environment, I'd opt for the latter as there are no moving
parts.
--

Larry
Email to rapp at lmr dot com

On Tue, 25 Nov 2003 22:14:36 GMT, "Doug K7ABX"
wrote (with possible editing):

I also have used the regulating transformers at large commercial on shore
radio/computer installations. Sola was the brand we used, one on each leg of
3 phase shore power. Some critical units had small single phase
transformers mounted in the rack. They covered about 95-135 volts in for
constant output. However, they take several cycles of power change for the
change to be seen at the output. I got into trouble having a large UPS unit
feeding the transformers, as the transformer change was slower than the UPS
and we got into a voltage bucking problem. Ended up taking the transformers
out and just using the UPS. Do a web search for Sola line regulator
transformers (they are really a mag amp autotransformer device). E-bay has
them from time to time.

Doug K7ABX

I think there are two kinds. One type uses a swinging core in the
transformer and works by adjusting the output voltage. The other uses
what is known as a "ferroresonant" transformer which works by
saturating the core at resonance with a non-polarized capacitor which
keeps the output steady regardless of input voltage swings. In a
marine environment, I'd opt for the latter as there are no moving
parts.
--

Larry
Email to rapp at lmr dot com

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.)