Hi Randy: You might be right... it's been awhile since I did anything electronics-related, and I've got a mind as sharp as toasted cheese. So I looked it up, and you are right... it's a simple voltage clamp, and it would prevent you from cooking the batteries. A regular 3 amp 50PIV diode in series will prevent current flowing backward (but I think there's a little bit of current loss from the diode) while the zener clamps the voltage at a maximum level (depending, I would imagine, on the type of zener that you use) I guess I was thinking that zeners were lower-loss than regular diodes... I thought I read that somewhere, but I can't say for sure. I've got all the parts for building my own rigid solar panel, but it's one of those projects that I haven't got around to finishing it yet, but it's on my list. Thanks BG -- Brian Gilbert Marine Media M17 "Tiny Dancer" (ex "Stargazer") (423)876-9990 3404 Hartford Drive Chattanooga, TN 37415 www.sailingsmall.com on 7/19/05 12:45 PM, RandyG at RandyG@cite.nic.edu wrote: Hi Brian, Saw your post to the MSOG list and was thinking you might have your definitions for diodes reversed. I believe a normal diode allows the current to flow in only one direction and a zener diode is used to limit/clamp the voltage to a not-to-exceed voltage value. If this is true, then a normal diode would go in series between the battery and solar panel and the zener diode would go in parallel across the solar panel. What do you think? Randy Graves M17 #410