Fast zener diode substitute
in [Design]
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From: langwadt on 6 Feb 2010 17:52 On 6 Feb., 23:06, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sat, 06 Feb 2010 22:58:00 +0100, Yvan <killef...(a)invalid.invalid> > wrote: > > >I decided to built this: > > >http://notes.ump.edu.my/fkee/e-Magazine/Elektor%202004/Articles/E/e04... > > >It keeps the battery a little bit active, preventing sulphation by > >loading the battery with a hefty current (40 A) for a short interval > >(50 ?s) approximately every two minutes. > > >But they used a fast zener diode (BZT03 27V) across the FET for > >protection, as rather large voltage spikes can occur when the FET > >switches off. > > >I can not find this diode where I am, so can you suggest a substitute? I > >guess I can not just put regular 27V zener diode here? > > A zener is pretty much a zener. I've never heard of a FAST zener. Use > any similarly-rated (voltage, power) zener. > > I wonder if the circuit actually works, chemistry-wise. > > John is the zener really needed?, if that little zener can handle the spikes, surely a big avalance rated fet can too -Lasse
From: Martin Riddle on 6 Feb 2010 18:20 "Yvan" <killefitz(a)invalid.invalid> wrote in message news:hkkrnj$hlo$2(a)news.eternal-september.org... > Nedavno John Larkin napisa: > >> How will you know if they work or not? >> The pulsed desulphator sounds bogus to me. > > > I have two old, unused car bateries. I'll connect desulphator to it, > and > wait for a month to see if it works. > They actually do work, but may take more than a month and the battery will have reduced capacity. Discharging and charging during desulfation seems to help the sulfur to get reabsorbed back into the electrolyte. Cheers
From: Jamie on 6 Feb 2010 18:57 John Larkin wrote: > On Sat, 06 Feb 2010 23:35:58 +0100, Yvan <killefitz(a)invalid.invalid> > wrote: > > >>Nedavno John Larkin napisa: >> >> >>>A zener is pretty much a zener. I've never heard of a FAST zener. Use >>>any similarly-rated (voltage, power) zener. >> >>Other opinions? >> >> >>>I wonder if the circuit actually works, chemistry-wise. >> >> >>I do not know, but I decided to try. I will also make this: >> >>http://home.comcast.net/~ddenhardt201263/desulfator/n_channel_schem.gif >> >>More info here: >> >>http://home.comcast.net/~ddenhardt201263/desulfator/lowpower.htm > > > How will you know if they work or not? > > The pulsed desulphator sounds bogus to me. > > John > after looking at the GIF, that is not a zener that he's looking for. its just a Fast recovery diode of 6 amps with a Vr(rms) of 70v, Tr(recovery time) of 150nS with 100pf This is nothing special..
From: Jamie on 6 Feb 2010 19:09 Yvan wrote: > Nedavno John Larkin napisa: > > >>How will you know if they work or not? >>The pulsed desulphator sounds bogus to me. > > > > I have two old, unused car bateries. I'll connect desulphator to it, and > wait for a month to see if it works. > > If D2 is the diode you are referring too, it's not a zener.. it's fast recovery diode of 6 amps. I am going by the image of the GIF you posted earlier as you stated it was the connected to the FET.
From: Ban on 7 Feb 2010 00:15
"Yvan" <killefitz(a)invalid.invalid> schrieb im Newsbeitrag news:hkkol8$fo4$2(a)news.eternal-september.org... >I decided to built this: > > http://notes.ump.edu.my/fkee/e-Magazine/Elektor%202004/Articles/E/e04b020.pdf > > It keeps the battery a little bit active, preventing sulphation by > loading the battery with a hefty current (40 A) for a short interval > (50 ?s) approximately every two minutes. > > But they used a fast zener diode (BZT03 27V) across the FET for > protection, as rather large voltage spikes can occur when the FET > switches off. > > I can not find this diode where I am, so can you suggest a substitute? I > guess I can not just put regular 27V zener diode here? > Yes put a 3-5W 27V zener. If diodes use the zener effect, they are always very fast, because no charge needs to be removed. This is valid for z-diodes above 8V rating. The circuit discharges the battery, in one year with more than 30Ah, together with the self discharge rate there will be 0 capacity left after a year for a normal 45Ah, this is certainly not a good idea and won't prolong battery life at all. Better to get a trickle charger and keep the battery fully charged during the storage time. The article goes back to the seventies BTW and was extensivly discussed and the circuit was considered pretty much useless. ciao Ban |