[VAC] Re: transformer/converter question

[Jim Dunmyer <jdunmyer@xxxxxxxxxxx>]

Joy,
 The TrueCharge seems better in some ways, as you mention below. As I
don't plan on using anything except conventional lead-acid batteries,
it's a moot point for me. Conventional L/A batteries are still the best
deal going if you consider electrical storage as the main point. (AH/$)

The Charge Wizard is a plugin gadget that turns the Inteli-Power
converter into the smart charger. Apparently, the microprocessor resides
in that little box. The C.W. also has a pushbutton to force the mode
selection and an LED to indicated its mode.

Other than the battery type selection, I see no real functional
difference between the StatPower and the Inteli-Power
converter/chargers. The former is a bit harder to mount, as it should be
vertical for best cooling. Because of the way these things work, I'd
suspect that the I.P. would also compensate for low input voltage and
would not be affected by an off-frequency supply. The latter is
important for some of us if we were figuring on charging the battery by
plugging it into a genset for a few hours. Ferro-Resonant converters
such as our UniVolt won't work well if the supply is off-frequency.

Additional advantages of both the S.P. and the I.P. is the smaller size
and very light weight, about 5# instead of the 30# UniVolt. The reason
they're so light is because they use what is called "switching
technology" instead of "linear". They rectify the incoming AC to make
DC, run that through a high-frequency inverter to make AC at maybe
25KHZ, step the voltage down in a very small transformer (transformers
work much more efficiently at higher frequencies), then rectify it back
to DC and regulate the output. This is exactly the same technolgy as is
used in your computer power supply, so it's nothing new or mysterious.

A regular clampon ammeter for AC will not work for DC. Best is an
ammeter that you physically place in series with the load, but they do
make ammeters that slip over a wire to read DC current. They won't read
real low values, but they do come in 2 versions (some are combination
units) that read 75-0-75 and 500-0-500 so you can check alternator
output and starter current draw.

To read real low currents with your clampon AC ammeter, loop the wire
through the jaws several times. Each loop multiplies the reading, so if
you have 3 loops, the reading on the meter will be 3X actual current
draw. My meter came with a "splitter" that has a combination
plug/receptacle on one end, a short cord, and a thing on the other end
with 2 loops for the clampon jaws. One loop is 1X, the other is 10X for
reading very small currents. It's real handy for checking out a device
that plugs into the wall, as you don't have to get inside to get the
jaws around ONE wire. 

Again, whether YOU can benefit from one of the new smart chargers
depends a lot on whether you depend on your batteries for more power
than at a typical lunch-time stop at a rest area. If you always have
power at a campsite, it's probably not worth replacing the UniVolt. If
you want your batteries to be treated RIGHT and you actually USE them
for a day or 2 (or more) at a time, then a good 3-stage charger should
be on your shopping list. And, if your UniVolt needs replacing, you'd be
foolish to consider anything else, as the price for an Inteli-Power
isn't much higher than many conventional converters.

                                             <<Jim>>