On Fri, 15 Mar 2013 14:37:01 -0500 "Bert Knupp" <[email protected]> wrote:
> As described in the factory’s shop bulletin, the relay is actually > supposed to open the circuit only when the potential between battery > #1 and ground drops below 10.0 volts, but keep them connected in > parallel so long as both battery #1 and battery #2 hold 10 volts or > better. In other words, the relay is “triggered” by having a (pos+) > feed to both coil terminals, one from each battery. If one battery > begins to run down, it creates a difference in potential (voltage) > between the two batteries, opening the relay so #2 gets cut loose in > order to stop it from running down #1. > Otherwise, any plain old SPST continuous-duty relay (like a headlight > or foglight relay, as somebody suggested) could be used, intended to > open any time the system is not charging. The circuit from > GermanSupply does that, I believe. That’ll work, but it’s less > elegant. This IS a German system, after all! Eleganz über alles! The relay you have *IS* a plain old SPST relay. http://www.texasindustrialelectric.com/relays_0332002156.asp In order to do what you want there will have to be additional circuitry involved. Especially since the "drop out" voltage on this relay is 1.5 - 4 VDC. Once it's closed it won't open again until voltage drops to essentially completely dead for a car battery. The "pick up" voltage is 8VDC so if one battery were at a solid 12VDC the other would have to be at 4VDC to *ENERGIZE* the coil and CLOSE the contacts. That's the reverse of what you want. I think I know how to make it work but I need to flesh it out a bit. I'm not sure it will work with *this* relay though. I'll get back to you. Can you put a copy of the service bulletin (translated if it's in German) so we can see it? G2 -- Visit the VintagVW archives at http://mail-archive.com/[email protected] --- You received this message because you are subscribed to the Google Groups "VintagVW - Air Cooled Volkswagen Discussion List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/vintagvw?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
