Keeping relay energized for long periods


#1

I am using this relay ( https://www.digikey.com/products/en?keywords=PB1121-ND ) to connect/disconnect a small (7W) solar charger. The charger is connected via the NC pins, so the relay is activated when the battery is fully charged, and released when charging is needed (or at night). In some relay spec sheets, I see warnings about leaving a relay energized for excessively long periods. I don’t know how long that would be. Are we talking about minutes, hours, days? In my application, it would never be energized for more than 8 hours at a time, and it would not be too difficult to interrupt it periodically if necessary. If interruptions are recommended, how often, and for how long?

Thanks.


#2

@couldabin, for this type of application, you should really look into “latching” relay: ( https://en.wikipedia.org/wiki/Relay#Latching_relay )

Using the PB1121-ND as reference, here a few options, that might work as a drop in.

https://www.digikey.com/short/ptdw9d

Regards,


#3

Thanks for the links. I had considered latching relays but decided to use a monostable instead because I didn’t want to build two snubber circuits. Not the wisest decision, perhaps, but that’s where I am. So … to the question of how long that relay can be energized safely – are there any rules of thumb? Thanks.


#4

@couldabin, in this case of this relay, the coil will be using “200 mW” (pretty small) so as long as that heat can escape the system it’ll be fine for extended use.

Regards,


#5

Great. Thanks for your input.