Battery and backup battery circuit design

Discussion in 'Power Electronics' started by jeffpkamp, Nov 4, 2016.

  1. jeffpkamp

    Thread Starter New Member

    Jul 31, 2013
    I am making my own wifi thermostat using an esp8266, and would like it to be cord free. I have lots of 2000ah lithium ion batteries that individually should be able to run the thermostat for weeks if I program it right.

    I would like to set it up such that it will run exclusively off of a single battery until the voltage reaches a certain point, and then switch to the second battery and send me some sort of signal, at which point I'd take out the primary battery and charge it while it runs on the backup battery. I feel like I could probably do this using the microcontroller and a switching relay, but I was curious if there was a way to set up a passive circuit that would perform the same function.
  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    You can use a CD4016 quad switch, it will be able to supply a max of 10mA.
  3. crutschow


    Mar 14, 2008
    There are quite a few ICs designed for that purpose.
    Perhaps one of these would work for your purpose.