Automatic Switch for 12V DC Backup Systems - DIY

Thread Starter


Joined Jul 11, 2018

Total newbie, I'm looking to create something like the product linked here -->
Can anyone guide me to to a starting point? or do anyone know whats the part name for the switch? I can buy this product, but seem a bit steep, plus i want to learn, maybe theres a better option.

My main purpose is to have a battery system (12v deep cycle battery - to 1000w inverter for 240v equipment) automatically goes on when my 240 Volt mains power goes out, the power failure switch will turn on a 12 Volt DC backup system. So it can run my aquarium water pump and heater (in 240volt).

Any help is appreciated.

Kind regards,


Joined Feb 20, 2016
For a start, what is the power requirements of the equipment you need to back up, and for how long?
That 12V backup unit linked is a low power supply.
Do you need 240V or can everything run directly off the 12V?