Lee, Indeed, I did not think about that "feature" of Christmas bulbs. But I do know that they will only fuse shorted if a high voltage is applied, not near their regular 2.5V operating voltage, otherwise every time you plug the bulbs in there would be several that light a little early and get a bit higher resistance and voltage and those would fuse. I would need to check, but I expect that it will be several tens of volts (like 50V or higher) before the insulation of the "fuse wire" will turn the bulb into a short. I expect that when that happens, the zeners will get too much current and blow. Now zeners are also known to fail shorted, so something is going to give in short order. I will need to test what happens to the fuse wire if it receives over-current. These strings have a plug-mounted fuse of 3A, so the wire should at least be good for 3A ;-) BTW, I found the spec for the bulb and it is 2.5V 200mA.
Cor van de Water Chief Scientist Proxim Wireless Corporation http://www.proxim.com Email: [email protected] Private: http://www.cvandewater.info Skype: cor_van_de_water Tel: +1 408 383 7626 -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Lee Hart Sent: Tuesday, January 07, 2014 9:23 AM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Free bulbs for zener-reg balancer Cor van de Water wrote: > I know that Lee has posted regularly about his zener+bulb balancer > and today I was finally making the connection while freeing our > Christmas tree from its light strings... > > I have no clue why they strung *12* strings of *50* lights each in a > 6-ft tree. No wonder it consumed somewhere around 260 Watts. Maybe they lived in Minnesota. Excess power usage in the winter isn't waste -- it heats your home! :-) > While unstringing, I was wondering what to do with the removed lights. > These are 2.5V lights that draw about 22W per string, approx 180mA > according to my Kill a Watt meter. > Then it hit me - these are probably perfect to use in balancers. That's not a bad idea! :-) Though there is one shortcoming: These bulbs are designed to fail *shorted*. If one burns out, it shorts so the rest of the string will still light. That would be bad news if it's across a battery that can supply unlimited current. You'd have to experiment with a burned-out bulb to see just how high the current gets, and if it would be a safe failure. -- "Obsolete" means nothing more than "the salesmen would prefer you buy something else." -- Dave McGuire -- Lee Hart -- See my Xmas projects at www.sunrise-ev.com/projects.htm _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA) _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
