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Battery Life!?

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qdn

New Member
Generally, the milliamp-hour would determine the battery life. For example, if your battery is rated at 1000mAh, and your circuit demands 100mA from the battery, then your battery is functional for about 10 hours.
 

stevez

Active Member
The reading I have done suggests that mAh rating is a point of reference tied to specific conditions and if your situation duplicates those conditions you can expect to reasonably predict battery life. The problem usually is that actual conditions are different and as I understand it, the battery life will be different. That doesn't mean that mAh ratings are meaningless - just that you might need to look at battery manufacturer's information to understand a bit more before you can accurately predict life. As I recall, Energizer and some of the other popular manufacturers had really good information on this subject.
 

bountyhunter

Well-Known Member
usually, the ma-hr rating is accurate at load current rates not higher than about c/10. As you increase load current (faster discharge), the A-hr capacity reduces. Battery makers usually publish curves showing the varying A-hr rates for different load current rates.
 

bountyhunter

Well-Known Member
that means that Battery Discharge Depends Only On Load current, and not on the time utilasation of it..that is if my load current is high the battery will discharge at a faster rate, n if my load current is low that battery discharges slowly???
It means that at higher discharge rates more energy is wasted internal to the battery in heat and you give up battery capacity (A-HR) if you want high discharge rates. The battery makers publish the curves for this. The point is, rated A-HR capacity is usually for discharge rates of about c/10 or LESS.
 

Electronworks

New Member
Adding a few more comments to this arguement:

If you have a 1000mAhr battery and you take 1mA out of it, it should theoretically last for 1000 hours.

Likewise if you take 10mA out of it, it should last 100 hours.

However, generally as the previous posters have said, if you take 10mA out, the life will be somewhat less than 100 hours. The higher the load current, the more your mAhr rating should be reduced.

The numbers above are just to make the sums easy. Look at the manufacturers datasheet as they have lifetime curves of constant resistance and constant current loads.

In addition, the battery will have a certain amount of self discharge. If you put a battery in an appliance, do all the calcs and come back in 10 years time, your battery will probably be flat, regardless of load. this will be due to self discharge. Generally this is not an issue though.

If you need 10 years life, Lithium Thionyl Chloride batteries are about the best you can get.

Hope this helps..:p
 
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