Advice on low power relay

Hello all,

I'm fairly new to Arduino and all of its many shields and accessories so forgive me if this is an easy question.

I'm working on a project where an Arduino is used to monitor certain aspects of a battery that is connected to a MPPT charge controller. Given the very limited power available, the Arduino seemed like a good choice.

The setup I have arrived at requires the Arduino to switch a relay when certain conditions are met. Unfortunately this condition is also the "prevailing" condition on a sunny day, and because I am using a mechanical relay this means a constant power drain from the relay (I was surprised at how much power these require!).

I would like to ask if there is a different type of relay which requires much less power when it is "switched on" than a mechanical relay? Ideally something that only requires power to switch on or off, not when it is actually switched to either state.

Does such a thing exist? What is my best option here? I need a relay that I can switch on (and keep switched on) with almost no power available to do so :-)

Kind regards, Michael

Latching relay, standard part, go for a dual-coil type and it can be driven by two Arduino pins (via transistors and free-wheel diodes), one to switch on, one to switch off. The sort I've used recently take 40ms to switch, ie a few mJ of energy, and handle 16A at 240Vac.

A Dual-coil Latching Relay. Never heard of that before. Power to switch, no power to stay switched. Just perfect!! :-)

I found this right away. It's more complicated than I expected - lots of components, but it does what I need.

Thanks a lot for your reply, this really helps.

Kind regards, Michael