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Do batteries last longer with constant current draw or spiky current draw?

Or, as is implied by the accepted answer to "Making a battery last a long time in a microcontroller circuit", do some battery chemistries last longer with a constant current draw, while other battery chemistries last longer with a spiky current draw? And if so, which battery chemistries are which?

In other words: Say I have a microcontroller programmed to wake up and do a few things once a minute, and then go back to sleep for the rest of the minute.

Which kind of batteries last longer with minimum capacitance across the capacitor (so the battery sees a big current spike once a minute)?

Which kind of batteries last longer with a big capacitor (or some kind of LC filter) hooked up to battery (so the MCU pulls a big spike of current from the capacitor once a minute, and then the battery very slowly trickle-charges the capacitor)?

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Buy a pack of batteries and test it. :) Build a circuit that draws a spiky current and then connect a resistor across another battery to use the same average power. –  endolith Jan 20 '11 at 22:30
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3 Answers

This is a very good question and I don't have a good (complete) answer. So I'll just give you a tidbit one of my old bosses used in a design. There is a certain type of battery with very high internal resistance that he used for a long-life application. Since it's high resistance, it has low leakage and its charge won't dissipate well on its own, but you can't source a lot of current from it. Since it was a periodic application (similar to yours) he paired it with a supercapacitor. The cap would charge up and when the uC was ready it would turn on, perform its actions.

But for the life of me I can't remember the words he used to describe it. I've tried searching for low leakage, high internal resistance and other terms I thought it was but I can't seem to find exactly it. It wasn't a coin cell, but more like a AA (but it certainly wasn't that form factor). I perused the Wikipedia article in Lithium batteries and the closest I could find was the Lithium-Iodide battery. There's plenty of info in that article as well:

http://en.wikipedia.org/wiki/Lithium_battery

Many different chemistries and a comparison table. Good read.

Good luck!

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You might want to go look through the archives of Consumer Reports (you'll need to be a member to see everything). They've done a lot of battery longevity testing over the years, and when the recent generation of batteries intended for non-smooth draw applications came along they had a bit of catching up to do in their testing. It might behoove you to read up on what they've done.

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For alkaline, it matters how much the peak is. Past a certain point the resistance goes up and you loose power there.

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Any idea what this peak is for some standard cells? The closest indictor I've seen for this is Energizer's " Battery Selection Indicator " in all their datasheets, and they are qualitative. –  tyblu Jan 16 '11 at 6:33
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