Is it possible to power relay and relay circuit with same battery?
Will the battery last for longer duration if its the same for both?

 

Yes, it is possible to power a relay with the same battery the relay will be switching to power something else.
No, it will not improve the battery life to power more things from it. Any load you add will necessarily use the battery’s capacity faster, not matter what that load happens to be.

 

Thanks for the reply. So, you mean to say that if I use separate batteries for circuit and load through relay then they might last longer?

 

Thanks for the reply. So, you mean to say that if I use separate batteries for circuit and load through relay then they might last longer?

No. they will last as long as the capacity for each to power the load they are connected to. There is no way to compare the two cases. Batteries have a certain power capacity which can be measured in Wh (Watt nours). 1 Wh is 1W of power for 1 hour, or 3600 Joules.

The loads will require a certain amount of power, so over an hour their consumption can be measured in the same way. If you have a battery that can provide, say, 10Wh and a load of 2Wh then (and this is very simplified) the battery should last about five hours.

It you have two 5Wh batteries, and divide your load into 1.5 and .5Wh, and power them separately, a battery for each, the 1.5Wh load will run for 3.33 hours, and the .5Wh load will run for 10. But, by the time you change the 1.5Wh three times, you’ve used four 5Wh batteries to run the total load for 10 hours.

This is exactly the same as if you’d used two 10Wh batteries on the combined load. In other words, the power requirements are the only thing that matters, and you can’t beat it by shuffling around batteries.

 

The relay just acts as a switch.
Other than the power required to power the relay coil, the relay has no other effect on battery life.

 

I got your point. Still I have doubt. Kindly don't mind. Let me explain about my purpose ..
I'm using two 9v batteries for a water level indicator circuit to drive a buzzer using relay. My point is that, if I use a single 9v battery for both (load and circuit), will the battery last as the above or it will discharge faster?

 

This is the same case as my example. The batteries will last as long as they can power the total load.
Since the buzzer probably uses less power in any given time (since it isn’t always running) that battery will last longer. But, since two batteries have twice the power capacity, in the end two will last twice as long as one.

If the buzzer is only occasionally sounds, you might not notice much difference in the time you have to change the one that current powers the circuit. That is, though it will go flat quicker, it might not be enough to matter.

But, if you use two batteries, the one on the buzzer will last much longer than the circuit battery and will be changed less frequently, but you change will change the circuit battery a certain number of times before the buzzer battery and in the final accounting you will use the same number of batteries with little difference.

 

This is the same case as my example. The batteries will last as long as they can power the total load.
Since the buzzer probably uses less power in any given time (since it isn’t always running) that battery will last longer. But, since two batteries have twice the power capacity, in the end two will last twice as long as one.

If the buzzer is only occasionally sounds, you might not notice much difference in the time you have to change the one that current powers the circuit. That is, though it will go flat quicker, it might not be enough to matter.

But, if you use two batteries, the one on the buzzer will last much longer than the circuit battery and will be changed less frequently, but you change will change the circuit battery a certain number of times before the buzzer battery and in the final accounting you will use the same number of batteries with little difference.

Thank you.