Hi Wayne.

01-Mar-03 04:10:00, Wayne Chirnside wrote to Matt Mc_carthy


  -=> MATT MC_CARTHY wrote to WAYNE CHIRNSIDE <=-

 MM>> 23 Feb 2003, 13:39, Wayne Chirnside (1:275/311), wrote to Roy J.
 MM>> Tellason:

 MM>> Hi Wayne.

 WC>>> with the stuff all the time. Downloaded a 39.4 Meg. PDF of
 WC>>> Digikey's catalog last night to find some hefty stud type
 WC>>> rectifiers to isolate the UPS charger from external battery.

 MM>> I wouldn't go the "diode route", and have to put up with the
 MM>> voltage drop.  I'd use a relay and wire it so energized is
 MM>> "open".

 WC> Depends on the actual voltages  of gell cell vesus deep discharge
 WC> lead acid though the relay idea is a good one. There are
 WC> disadnvantages to a relay too, expensive in that range of current,
 WC> pitting contacts.

what sort of currrent does the UPS draw?  headlight (etc) relays are good
for 40A, and are avaialble with normally closed contacts.

(starter relays will handle around 400 but finding one that's open when
energised could be hard - you could  power the big relay from the extra
battery and use a smaller relay to switch it)

40A would probably get you around 400VA at the output - enough ?

 -=> Bye <=-

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