# Estimating Battery Life

I am working on a design that needs to operate outside on two AA batteries for at least a year.

I have optimized the design to reduce power and using a spreadsheet analysis I now have an average current consumption. I should be able to verify that is right by monitoring a prototype for a while.

I have the following pieces of information:

How can I take this to create a realistic estimate?

I think it is perhaps reasonable to use the average environmental temperature $Tave$.

Note - I chose Duracell simply as an exemplar of a quality battery. I wouldn't need/want to consider poorer-quality batteries.

Many thanks!

Update - average power consumption is 1.11mW.

• what temperature range? <0'C? – Tony Stewart Sunnyskyguy EE75 Jan 2 '18 at 17:26
• mAH is not a measure of power, it is a measure of electrical charge/battery capacity. For Pave I think you mean mW or equivalent power draw? Same goes for Psupply — it should be in mAH but is not a measure of power, but battery charge/capacity. – Murey Tasroc Jan 2 '18 at 17:31
• 1.11mW sounds high. If your goal is roughly 10k hours, that would be 11 Wh of energy, or almost 4 Ah @ 3V -- a bit much for AA cells. You need to be about an order of magnitude lower than that. Typical alkaline AA capacity of 2500 mAh / 10k hours = 250 uA average consumption. – Dave Tweed Jan 2 '18 at 17:51
• @Andy, don't bother worrying about the nonlinearity. Temperature effects, etc, mean you'll only get an order-of-magnitude estimate anyway. Just do a rough calculation and then give yourself a good engineering margin. – The Photon Jan 2 '18 at 17:56
• I have alarm bells at mentioning of a DC-DC converter for something which needs run a looong time from batteries. What does your application (without converter!) need as voltage and what does it use as current? – Oldfart Jan 2 '18 at 18:01