From owner-qrp-l@Lehigh.EDU Sat Nov 28 21:26:27 1998 Received: from fidoii.CC.lehigh.EDU (fidoii.CC.lehigh.EDU [128.180.1.4]) by oucsace.cs.ohiou.edu (8.8.5/8.8.5) with ESMTP id VAA12099 for ; Sat, 28 Nov 1998 21:26:26 -0500 (EST) Received: from LOCALHOST ([127.0.0.1]:3015 "HELO Lehigh.EDU" ident: "IDENT-NOT-QUERIED") by fidoii.cc.Lehigh.EDU with SMTP id <53664-66868>; Sat, 28 Nov 1998 21:23:58 -0500 Received: from nss4.CC.Lehigh.EDU ([128.180.1.13]:4388 "EHLO nss4.cc.Lehigh.EDU" ident: "IDENT-NOT-QUERIED") by fidoii.cc.Lehigh.EDU with ESMTP id <53352-66868>; Sat, 28 Nov 1998 21:23:26 -0500 Received: from smtp2.erols.com (smtp2.erols.com [207.172.3.235]) by nss4.cc.Lehigh.EDU (8.9.1a/8.9.1) with ESMTP id VAA276010 for ; Sat, 28 Nov 1998 21:23:25 -0500 Received: from default (207-172-250-199.s8.as13.anp.erols.com [207.172.250.199]) by smtp2.erols.com (8.8.8/8.8.5) with SMTP id VAA19338; Sat, 28 Nov 1998 21:26:44 -0500 (EST) Message-Id: <3660AFE9.3D70@erols.com> Date: Sat, 28 Nov 1998 21:22:33 -0500 Reply-To: wa8mcq@erols.com Sender: owner-qrp-l@Lehigh.EDU Precedence: bulk From: Mike Czuhajewski To: "Low Power Amateur Radio Discussion" Subject: Cyclon lead acid cell caution MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Transfer-Encoding: 7bit X-To: QRP forum X-Cc: Wes Hayward X-Mailer: Mozilla 2.01KIT (Win95; U) X-Orcpt: rfc822;qrp-l@fidoii.CC.Lehigh.EDU X-Listprocessor-Version: 8.1 beta -- ListProcessor(tm) by CREN Status: RO 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