Battery life for long term deployment
As far as I am aware, off-the-shelf batteries are not designed for long lifetime use, in the order of years. Yet they are being used for long term deployment in WSN. I’ve seen theoretical projections of how long low power wireless motes can last. But there still seems to be an unknown quantity on the profiles of batteries, when used for a long time by wireless motes, drawing µA current…
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There has been talk surrounding using energy harvesting to recharge microbatteries which supposedly last thousands of cycles and can be self-sufficient. US companies like Cymbet and Infinite Power Solutions claim their rechargeable batteries can last years by hooking up an e-harvesting method – and they are absolutely correct. But both companies offer batteries that cannot provide above 1 MILLIamp hours of capacity – that’s a problem.
Most of us sensor developers need capacities of 10 to 100s mah with expectations for recharging under 30 mins. Which is why I was interested in a recent rumor, along with a demo I heard of this past fall, that a “microbattery” company is launching a 10mah thin and small battery, complete with a wireless energy harvester to charge the battery. The company, Planar Energy Devices, already demonstrated the same battery (I think) during the Embedded Systems Conference and powered a temperature sensing network – it lasted for hours, two day straight AND they then showed no degradation at the end of the show.
Had a look at their website, it seems that the battery need to “harvest” energy from their wireless recharger. Interesting, will definitely want to find out more about it.