Michael K Johnson wrote:
Ah! The contactor I have is an Alltrax SOL-48V-400A; 48V coil and contacts. Rated for 10,000 cycles.
And that's at full load. You're normally switching it at lower currents, so it lasts even longer. 100,000 cycle life is typical for industrial grade contactor at rated load. Automotive grade stuff is typically rated for only 10,000 cycles. That's why they can advertise such absurdly high ratings for tiny automotive relays.
If you're worried about contact life, you can put a "snubber" across the contact. At this power level, it's a 0.1 ohm resistor and 1000uF capacitor in series across the contact. The "resistor" in such a circuit is really just the capacitor's own ESR plus a pair of 6"-12" #24 wire leads on the capacitor.
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