Battery Calculations

computer guy

I am working on a project (which I hope to turn into a product).
My biggest concern with making it into a product is size (it needs to be as small as possible).

I'm looking at using a Li-ion or Li-po battery as it needs to be rechargeable.

My question is, what is the best way to get accurate current requirements.
Going off of the nominal current draw in data sheets has me working out that one battery I am looking at will last less than 10 minutes. (The battery is 3.7v at 110mAh)
Obviously this isn't going to work for me.

It needs to last at a minimum 12 hours.

I don't want to over compensate though.

So how can I get an accurate mAh reading for my needs?


Thanks

Heater.

First thing you need to do is understand how to get your processor and other circuits to use the minimum power.
If you are using a Prop you can run it with the slowest posible clock speed. Perhaps turning up the speed for brief periods when you need to do some work.
Then you will want arrange that your code is not running idle loops when waiting for something to happen which wastes power doing nothing. So use waitpe and such instructions instead of polling pins for example. A Propeller cog waiting on a pin uses a lot less power.
Now you will have a system whose power draw is not constant. So you will want to measure the current draw in it's different states of operation, working hard, waiting on external event, etc. Then it's up to your application, you have to estimate how long it will spend in those various states and start adding up the power draw over time.
Don't forget the power in external components, a simple pull up resistor eats power so make it as big as you can get away with.
At the end of the day you want to measure what is going on in real usage.