Determine current usage with periodic bursts of current draw

I have the following display: http://www.pervasivedisplays.com/products/144 and am trying to determine how long it will last on a 3V button cell battery with 220mAh battery.

My questions though is how to determine the equivalent continuous current draw based off of a known current draw for a known time at a known interval. The display takes 2 seconds to update and it will need to be updated once every 10-15 minutes. And the display specifies that it draws 20mA while updating.

I know if you take a usually battery with say a 10Ah rating that means you can pull 1 amp continuous for 10 hours, but I am not sure how to calculate usage time with periodic current usage bursts.

Thanks in advance!

Your duty cycle is 2 sec/600 secs. Find out how long it will last if it updated continuously, and then divide by the duty cycle.

Awesome, thanks a ton!

20mA/update = 10% of battery capacity.
Here's some # from Panasonic
http://www.panasonic.com/industrial/batteries-oem/oem/primary-coin-cylindrical/br-cr.aspx
Only expecting 0.03mA or 0.1mA, 0.2mA current draw.

Good article from TI on using coin cells too:

Conclusion - add a 100uF cap in parallel with the battery.

The actual calculation is integration - summing the product of current and time,
to give total charge. Typically you just need to do this for one cycle and then
divide charge-per-cycle by time-per-cycle to get average current.

add a 100uF cap in parallel with the battery

Excellent articles about current draw from coin cell batteries and maximizing efficiency; thanks!

The actual calculation is integration

Ok just as an exercise in learning some thing here:

So if I take the integral of current with respect to time from t = 0 to t = 2 seconds i would get the charge used over that 2 second interval correct? If so I used .02 as my current and got a charge of 40 coulombs.

And so if I take that 40 and divide it by 2 I would get back to where I started at 20mA correct?

Interesting to work out the math but I'm failing to see how I could use that to get the answer I achieved by using what Keith said in which I took (220mAh/20mA) and divided that by (2/600) to achieve a total of 3300 hours or 137 days.

40mC, not 40C...

Thanks! Hahah good point about the mC. I was thinking the wrong order of magnitude...

That integration only works out if the battery has low enough ESR to support the discharge rate.