I am seeing relays reach their end of life much sooner than expected (and in a catastrophic manner). Specs on the relays are 24VDC 30A SPST NO. I am putting 10A to 20A of resistive load on said relays. They are lasting roughly 35000 cycles under these conditions before failing (speced out at over 250K).
In looking at the design, it has been noticed that instead of breaking "+" or "-" to said relay coils, we're simply letting the power supply "die out" as needed.
In speaking with the applications engineer for said relay MFG, they have no comment on this, no data to present and really nothing to say about it. As far as their concerned, this is untested. I've attached two diagrams to illustrate
Does anyone have experience with this? Anyone have thoughts on this?
Note: Assume Q1 and Q2 are supplied with base current once +5VDC is available to power the micro