Robert Bruninga via EV wrote:
spring-wound bathroom timer ... works fine for AC or DC ...15-20 amps.
Reminder: But ONLY AT LOW VOLTAGE DC. Use it once at any higher voltage on DC, and when the contacts open, and arc will not only burn it up, but probably catch it on fire. Solution of course is to put a snubber resistor and capacitor across the contacts. But without that, it will not open a HVDC circuit,... just arc and burn.
A good point! As a rule, an AC rated contact is good for about 1/4 the voltage on DC. Thus the 120vac/30vdc rating that's frequently seen. In the context mentioned in this thread (testing individual cells), the AC contact is fine because the DC voltage is well under 30v.
If you have to switch a *high* DC voltage, a snubber helps a lot, particularly with inductive loads. I described snubbers at http://www.sunrise-ev.com/LeesEVs.htm#snubbers. I also described some simple battery testers at http://www.sunrise-ev.com (about halfway down the page at "Lee's EVs". :-)
Or, use the AC-rated contact to switch a relay or contactor with contacts rated for the voltage and current you are actually switching.
-- Any intelligent fool can make things bigger, more complex, and more violent. It takes a touch of genius, and a lot of courage, to move in the opposite direction. -- Albert Einstein -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
