Relay life - Degradation after 4.7 million cycles

 Just to recap:

• 1.8 million cycles switching a 2 Amp constant current
• Added an RC network giving some 10Amps on contact closure falling to 2Amps constant current
• Ran for a further  1.3 million cycles
• Got impatient, reduced R to give >10 Amps on contact closure falling to 2Amps constant current
• Ran a further 1.6 million cycles (Run 6 and onwards below)
  

 Total cycles now 4.7 million. For the 2.9 million observations with the RC network we see:

 

The analysis of variance by group shows run 11 had an increase in average contact resistance of around 8% and much greater variability. 

 

The 15% increase from run6 to run11 means the relay contacts are dissipating 32% more heat when closed.

I'm going to hit a total of 5 million cycles with the next run. 

73's