WiFi relay to DC motor

dc motorrelaywifi

I'm trying to use a 12 volt WiFi relay setup to control a 12 volt DC motor. The WiFi relay has eight 10 A SPDT relays in it and the motor is 15 A. I understand how to wire it directly to the two relays that are in the box, but I'm lost after that. Here are my questions:

  1. Since I'm using two 10 A relays at the same time to control the motor (positive through one and ground through the other), does this mean that I have a 20 A capacity with the relays?

  2. How else could I wire this up to increase the relay capacity (or run the signals from the WiFi relays) to other relays and protect the WiFi relay box?

Here's the info on the WiFi relay:


Here's the way I was going to wire it directly

Best Answer

  1. Combining several relays in parallel is not good, because the contacts do not switch at exactly the same time, and it will cause arcing at the faster one. Another thing is that the motor is an inductive load and needs more current than the rated \$15\,\mathrm{A}\$ during startup.
  2. Without modifying the existing circuit, it can be done with another relay with 12V coil and contacts rated for inrush current of the motor.

Edit: Two 10A relays in series can still carry only 10A. Theoretically it should be possible to double the current by merging more relays to operate like one larger relay, but is not possible as described above.

Possible wiring can be done like this, for example with 30A or 40A automotive relays:


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