subjecting a non rechargable battery to a low voltage charge

Submitted by John on Sun, 05/24/2020 - 12:17

I am building an extremely simple circuit to connect a load with a very small consumption (maybe 10mA constant with say 100mA for 1 second twice a day at 9 volts DC) to a rectified plug pack which supplies rectified 8.9 volts DC and I want to include a battery backup in case of power outage. I was hoping to just use an alkaline 9V battery as any power outages would only last for say 1 hour absolute maximum and be very infrequent rather than add components to the circuit and use a rechargeable battery. The battery is only present in case of a power outage.

Using schottke diodes I have measured a possible 0.7 volts being constantly present at the 9 volt alkaline battery. Alkaline batteries should not be charged but would 0.7 volts be a problem? Would a resistor in series to the battery help?


A power path controller is a circuit that will enable another source of power (battery in this case) when the primary power source is not available. I think this is the best way for your application.

  Joined February 12, 2018      696
Monday at 02:11 PM

Thanks Sourev

I was hoping to keep it as simple as two schottke diodes I will factor in a mosfet to ensure the battery is isolated.


  Joined May 16, 2020      5
Saturday at 05:25 PM

The useability of the MOSFET will reduce the voltage drop.

  Joined February 12, 2018      696
Monday at 02:11 PM