battery backup help needed

[anil_asdaq]

hi,

can i have safe battery backup ? I am using 6v 5ah battery as standby source. in my power supply circuit i have lm7808 and diode resistor and battery and lm2931 to get 5v constant output.

am attaching the schematic.
What happens if the power goes off for 2 days. Will the system start immediatel or how much time it ll take to start properly.

can any thing be done to this circuit such that even when the battery is flushed out completely, it doesnt pull the supply for long. the systems starts smoothly.

regards

anil

 

[anil_asdaq]

attachment

hi,

can i have safe battery backup ? I am using 6v 5ah battery as standby source. in my power supply circuit i have lm7808 and diode resistor and battery and lm2931 to get 5v constant output.

am attaching the schematic.
What happens if the power goes off for 2 days. Will the system start immediatel or how much time it ll take to start properly.

can any thing be done to this circuit such that even when the battery is flushed out completely, it doesnt pull the supply for long. the systems starts smoothly.

regards

anil

 

[Oznog]

Bunch of probs.
D9 and R23 don't look useful, it will only drop the source voltage to 4.3V. Maybe some reason for this?

The 6v battery needs to be charged by a higher voltage. But let's assume it's not rechargeable. It needs a diode for one so the power won't flow into it. But at 6v nominal, it may be at 7v or higher in practice. Being a higher voltage than the 5v reg, the circuit will always draw power from it and not the reg until the battery is drained.

Battery needs to be in front of the reg (in which case you need to use a Low Dropout (LDO) reg) with a low voltage drop Schottkey blocking diode. Or there are a few other solutions.