how to calculate the battery life span

[hemnath]

Lets say i have a battery with 3.5V, 1500 mAh. If i draw 2mA constant current from the battery.

If i draw continuously, the battery voltage will also drops. How many hours will it takes to reach the battery voltage of 2.5V?

Any formula available?
Please help.

 

[mvs sarma]

you could directly divide the maH capacity by 2ma as the current is small.
Each type of battery is provided with discharge graphs.
interpolation there would be reasonable at higher load currents.

 

[hemnath]

If i divide it with total maH by 2ma, it could be total battery hours.. Right?

But i want to calculate the no. of hours till the voltage reaches 2.5V.

 

[mvs sarma]

generally the calculations are given for useful voltage
.
for your need, interpolation the battery load graphs is the best way. You need to seek detailed datasheet of the concerned manufacturer.

 

[Audioguru]

Batteries are not all the same. Some will last longer than others. I bought some cheap Chinese solar garden lights that came with a Ni-MH rechargeable battery cell. Some of the batteries are pretty good and others are useless. The solar panels are the same.
Alkaline battery cells are also not all the same. Some are pretty good and others are dead and leaking in the store before they are sold.