Cyclon lead acid cell caution

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From: Mike Czuhajewski (wa8mcq@erols.com)
Date: Sat Nov 28 1998 - 21:22:33 EST


Wes Hayward posted the URL of Hawker Energy Products, I took a look at
the Cyclon application guide as he suggested, and it brought back lots
of memories. At one time the Cyclon name (no "e" at the end) was sold
by Gates, but it would seem that Hawker has taken over the product line.
>From their application guide it would appear to be the same thing.

Maryland Radio Center was a local ham store until it closed recently.
They used to have a "public junk box" which was a corner of the store
set aside for junk. If the wife made you clean out the basement and you
didn't want to toss the electronics in the trash, you could bring it
there, or take home anything that looked good, all free. We got all
sorts of electronics goodies from the public junk box over the years, as
well as dropping off a huge quantity from our own houses.

One thing that started appearing there was a large quantity of Gates
Cyclon batteries, mostly in the size that's the same as a standard D
cell. These are 2 volt cells, rated at 2.5 amp hours. We also started
seeing larger sizes show up at hamfests, and they still do. The Cyclon
series are sealed lead acid cells and made to have very low internal
resistance. This means that they can supply rather staggering amounts of
current--briefly!--to a short circuit. I looked up the Cyclon cells in a
catalog at the time, and seems to me the lowly D size Cyclon could
deliver 200 amps to a short circuit. Maybe my memory is faulty, or
perhaps they improved the design, since the Cyclon application guide I
just read says the D cell can supply 400 amps. That's four hundred
amperes to a short circuit directly at the terminals. Hint: do not
attempt this at home :-) That's based on an internal resistance of 5
milliohms (per the data sheet) at 2 volts for a fully charged cell.

The owner of Md Radio Center once accidentally shorted the wires on one
of the cells--most of them came shrink-wrapped in a set of 3 with wire
leads on them, to form a 6 volt battery. He reported that the wires
vaporized and the cells were destroyed, but not before spitting out
molten chunks of lead along with sulfuric acid. Fortunately no injury
resulted, although the cement floor did require some cleaning!

Some of the other Cyclon cells available, by type, amp hour capacity and
short circuit current are:

DT, 4.65 AH, 400 amps
X, 5 AH, 570 amps
E, 8 AH, 665 amps
J, 12 AH, 800 amps
BC, 25 AH, 1335 amps

All of these are physically larger than a standard D cell.

I still see Cyclon batteries at hamfests in this area, and I presume
they are available around the country. They make attractive power
sources and have great capabilities, but the potential for nastiness is
equally great :-) If you are going to be using these--or any relatively
large cell or battery of any type--it would be wise to place a fuse as
close as possible to the battery, and to keep the terminals well
protected and insulated so that nothing can short them directly.

Of course, if you have a short several inches away from one of those D
cells, it won't draw anywhere near 400 amps due to the resistance of the
wire. On the other hand, it probably will draw enough current through
those wires to make you wish you'd had a fuse there :-)

Let's try an example. Assume #18 wire is used, and a short occurs one
foot from the battery. That's two feet of #18 wire. According to the
wire tables in the ARRL handbook, #18 has a resistance of 6.51 ohms per
1000 feet, so 2 feet has a resistance of 0.013 ohm. Add that to the
0.005 ohms internal resistance of the fully charged battery, or 0.018
ohms total, at 2 volts, or about 111 amps. The handbook says that #18
has a current carrying capacity of 2.32 amps, a specification which I
believe is based on a specified, "acceptable" temperature rise. I'm not
an expert in this area, but I rather suspect that 111 amps would result
in an unacceptable temperature rise :-)

Again, the moral is to make sure that you have a fuse as close as
possible to the terminals of a rechargeable battery, and make sure the
terminals are protected so they can't be accidentally shorted.

(I mentioned some of this in my Idea Exchange column in the QRP
Quarterly several years ago, although I didn't give the information on
the larger sizes of cells or the #18 wire example.)

 --
73 and Queue Our Pea de WA8MCQ wa8mcq@erols.com


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