On Sep 26, 2009, at 12:23 PM, Harvey Norris wrote:
Because the (car) alternator has its field regulated, it is
designed to constantly produce 12 or 13 volts, probably even at the
lowest rpm available to it by idle of the automobile.
The PMG site however claims that high amperage extraction at low
rpms must be avoided as it will overheat the stator windings. The
one I am purchasing will be used for a small Brown's gas torch;
driven by a 10 hp lawnmower engine. What this means is that the
generator that developes higher voltage at higher rpms will have a
load that "kicks in" only after a certain rpm developes. This is to
be negotiated by the number of cells in series that the unit
employs. It would seem then that my variable speed drive will come
in very handy here. As noted with 40 cells in series, the
thermoneutral electrolysis point only being 1.4 volts/cell, this
implies that the load should kick in at 56 volts from the
generator, which is probably just under mid range engine rpm for an
automotive application.
HDN
You may be highly disappointed running at 1.4 volts/cell. I'd
suggest buying a cheap diode bridge, or 4 cheap diodes to make a
bridge, and then running the 40 cells (if 40 is the only number you
can try) on 120 V house current first. If you have a variable
transformer, then try running at various voltages just to see what
your best design point is. Variable transformers can be obtained new
for as little as $100. I bought a bench top model years ago and have
been amazed at all the things it has been handy for. I often use it
in series with a transformer cannibalized from an old battery charger
for low voltage stuff (I sometimes add my own secondary windings), or
a transformer from a microwave for HV stuff.
If obtaining hydrogen at minimum energy per volume is your goal, then
you may be better off running at 12 VDC regulated and 2.4 volts per
cell, or 5 cells in series to make a unit, and 8 units in parallel,
or some such series-parallel arrangement. For what it is worth, a
cheap and very good electrolyte I've found is made by saturating
water with ordinary lye, and then diluting it 3:1, i.e. with 2 cups
of water per cup of saturated lye.
For variable transformers see:
Ebay:
Just query "variable transformer"
Amazon:
http://tinyurl.com/yatya58
McMaster:
http://www.mcmaster.com/#variable-output-transformers/=3t4581
http://tinyurl.com/y92fe4j
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
