I can say from experience that the heads can be screwed down into the holders so that the edge of the screw cannot touch the battery cell. Since the screws are not directly under the cells, they can't touch the cell when fully inserted.
There are two ways that you can have battery short trouble: 1) A mounting screw digs into the side of a battery, penetrating the thin insulating cover, grounding the cell's container or "can". That shorts out the cells between that point and the negative terminal end of the battery pack. This can happen with either rechargeable NiMH cells or with Alkaline cells. 2) The spring on the base contact shorts out an Alkaline cell. This is not a problem with NiMH cells since they have a "can" covering the bottom and sides that is all part of the negative terminal, just like old carbon-zinc "dry" cells. But Alkaline cell chemistry reverses the terminals so the "can" is the positive terminal and the negative terminal is the insulated center electrode. To keep Alkaline cells looking and installing just like the older cells, manufacturers physically turn them upside down. What was the smooth bottom of the can on a dry cell they now stamp to look like the top of the battery, with a button for the positive terminal molded into the "can". Close inspection will reveal that there's no insulator separating that positive button from the rest of the "can". At what is now the bottom there is an insulated electrode that covers the negative end of the cell. The insulated electrode is attached to a disk that covers what appears to be the bottom of the "can" but which as actually insulated from it. Some manufacturers have an insulator around the edge of this disk just under the plastic sheath where it wraps around the bottom of the cell that separates it from the positive "can". If that sheath is broken, the spring in the battery holder can easily bridge the insulator and short the cell. One manufacturer moves the insulator up onto the side if the battery which eliminates that problem, but most of the cells that I've unwrapped show the insulator just under the edge of the sheath on the bottom of the cell where the spring will cause a short if the insulating sheath is damaged. (There are pictures of this in the KX3 Kit Assembly manual on the web site: http://www.elecraft.com/manual/KX3%20Kit%20Assembly%20Manual%20Rev%20F%20WEB .pdf See page 35, Figure 54) Obviously failure of the sheath at the bottom of alkaline cells is rare, since virtually all cell holders use a spring to contact the negative terminal, but it has happened. 73, Ron AC7AC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Gary Marklund Sent: Saturday, January 19, 2013 2:48 PM To: Phil Hystad Cc: [email protected] Subject: Re: [Elecraft] KX3 Battery Holder and Batter Removal I took this opportunity to install ribbons on mine, too. Was certain it was only a matter of time until I gouged a battery case. I'm also convinced the problem is more that the screw holes are not countersunk than screw length. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
