Mini Relay featherwing maximum capacity at 12v

[j15e]

I got a mini relay featherwing and I would like to know if I could wire a 3 amp / 12v dc pump?

The datasheet https://cdn-learn.adafruit.com/assets/a ... 1459367511 reads :

30 VDC, 2 A (Resistive)
110 VDC, 0.3 A (Resistive)
125 VAC, 0.5 A (Resistive)

- Is 2 amp the maximum rating even when the voltage is lower or is actually 60w the maximum load?
- A pump is reactive load so I should split this capacity in half? Then I would still be over the capacity (36w)?

I am pretty sure it would be safer to go with a beefier relay but I would like to understand and know what should be done when reading such specs and calculating for lower voltage?

[jps2000]

For sure 3V 20 A is not possible. So 2A can be considered as limit although there is a certain margin.
Be aware that a pump is a motor which has also inductive component and - more important - a motor drop much more current when starting. You may measure this current ( very short time only!!!) by blocking the motor. I expect this is then 10 amps or even more in your case - probably limited by wiring resistance and supply as well.
Conclusion: 30V 2 Amps is not sufficient

[adafruit_support_mike]

Switch and relay specs take a bit of getting used to because under ideal conditions, the voltage drop across the switch itself would be 0v. No voltage means no power dissipation at any amount of current, so an ideal switch wouldn't have an upper limit on current.

The current limit for a real switch tells you the "yeah, but how do I use this?" summary about the resistance through the switch and its ability to dissipate heat. Running a switch above its current rating is likely to make it run hot, which leads to a range of failures.

The voltage limit for a switch tells you how far the contacts are spaced apart, and how good the insulation is. All mechanical switches arc just before they make full contact, and just after they open. The trick is to move the contacts far enough apart that the arc will quench. AC power is self-quenching because the voltage drops to 0v twice per cycle, but DC can turn a switch into a tiny arc welder. The DCV rating for a switch is usually 10% of the ACV rating, or less.

High current also increases the chance that the contacts will weld themselves together when they make contact, which can be anything from a nuisance to a catastrophe depending on what the switch is controlling. That would be my major concern about running the mini relay above 2A, so I wouldn't recommend it for a 3A load.

[jps2000]

good informations Mike
However you can also weld with AC....

[adafruit_support_mike]

True enough.

[j15e]

So with the larger featherwing relay would it be enough? https://learn.adafruit.com/adafruit-pow ... eatherwing

From my understanding of the specs sheet, it can handle up to 8 A @ 30 VDC and my case would be 3A to 10A or + (at start) @ 12VDC, not enough capacity either? Or it would be OK to go a bit higher than the spec during start?

[jps2000]

This should be enough margin i think

[adafruit_support_mike]

Yeah, that one should work.