I’ve had a client ask about deploying a station at a site high in the mountains where there is no cell coverage, no wifi, DC power only, and humans are not present until June, and depart in the Autumn. They want to give the station the best chance of powering up and collecting data when migration is underway- so March through October. They would like the station to stop drawing power from November through February…so four months off, eight months on. Does anyone know of a power supply timer that would work for this? and if so, how best to set it up to ensure IT stays powered as well?
I don’t quite understand the motivation for keeping the station off from October to March but I wonder whether a thermal switch isn’t simpler and more robust? E.g., if the battery has the most stringent thermal constraints then use a mechanical thermostat to turn power on when the temperature is OK. This could allow the station to operate longer as well as shut it down if the temps drop too much in the march-october period.
I think (and this is the problem with relaying a message ;) ) that the concern is snow will obscure the solar panel more frequently in the winter months which would lead to poor battery maintenance and result in the system not rebounding when needed most in the spring. Secondarily was the concern that the cold temperatures could shorten the life of the equipment. I’ve told the client about the forum so hopefully they will join in the conversation.
Yeah, interesting… And I don’t want to discourage anyone else from posting info about an appropriate long-term timer. I just don’t know about one nor would I know how to test it.
I would still look at a solution that is driven by the conditions that they want to avoid as opposed to calendar days. Maybe two thermal switches in series, one at the solar panel to turn off if it’s snowed in and one at he battery if it’s too cold to function properly. Although perhaps the temperature is higher when the solar panel is covered in snow than when it’s exposed?
It sounds like they’re using an AGM battery and want to avoid having it oscillate between voltage cut-off and just a tad above that? So an ideal controller would cut out at some minimum voltage or SoC and not re-engage until the battery is say 90% full?
The Morningstar Sunsaver 10L or 20L solar charge controllers have a low voltage disconnect that sounds similar to what Thorsten proposes for the battery side. Automatically cuts off power to load when battery is at 11.5 and reconnects at 12.6v. No way to control when this happens and relies on the battery getting charged enough at some point, so results in brown-outs through the winter, before picking back up with consistent power in the spring. In the past, to extend the period of 24h power (or run through the winter at northern/snowy sites), we’ve added a second battery and/or second panel to increase storage/collection.