Power handling for UTV project - Relay selection



Jun 4, 2007
Hey guys, been a long time since I've visited the forum, but still very much a flashaholic :candle:

I'm working on a project that involves power distribution for a UTV - basically a relay box in which light bars can be switched on and off. Pretty straightforward. These vehicles have a typical noisy 12V automotive power system and they endure a lot of vibration and environmental elements.

Right now I'm laying out the board and selecting components. There are a few remote rocker switches, screw terminals, fuses for each circuit, and a flyback diode for each relay. My goal is to make it as small as possible, and still be able to switch 10A per circuit, with a 25A maximum draw.

When selecting the relays, my first thought was I'd have to use those giant socketable relays, however my searches on Digikey have led me to these little guys:

I bought one to experiment with and I'm astonished at how small it is, yet has a 30A current rating. It is easily 1/4 the size of a typical relay I've come across - maybe smaller.

1. Am I missing something with regards to relay ratings? Out of the pc-board mounted options, there doesn't seem to be a correlation between size and current capacity. Will the smaller one be less reliable?
2. Can you think of any other feature I should include in this box to protect the circuitry? The flyback diode was a "trick" I picked up here to quell voltage spikes from the relay field collapse. Anything else you'd add?



Flashlight Enthusiast
Jun 23, 2003
Southern USA
UTVs are pretty small, so I can't see a wire-economy decision driving using relays. And switching 10A does not present a switch challenge. In short... why use relays? Just wire and switch direct, using fuses of course.

I can't comment the relay selection to directly answer your question. But using good waterproof switches also addresses some of your core design goals as well.

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