Hi, AA cells are closer to 2000mahr. A lot depends on the discharge rate. Alkaline cells have about the same capacity as the LiFeS ells but the Li have a much higher discharge rate. Those numbers are for primary cells (non-rechargeable). Rechargeable cells have about 1/2 the capacity (that is a VERY rough approximation) of primary cells. Bob Kondner -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Michael Azarian Sent: Wednesday, June 30, 2010 10:02 AM To: [log in to unmask] Subject: Re: [TN] NTC - Solar Panels and small motors Eric, A quick Google search shows that a standard AA cell has a capacity of 400-900 mA-hours. If you run the fan off the two AA cells, how long does it last? Knowing that, you can estimate the current draw. For example, if it would run for 4 hours, and your batteries had a capacity of 600 mAh each, then the fan draws about 300 mA. It would probably draw more upon startup, but that would be for just a few seconds. Mike _____________________________________ Michael H. Azarian, Ph.D. 1103 Engineering Lab Building Center for Advanced Life Cycle Engineering (CALCE) Department of Mechanical Engineering University of Maryland College Park, MD 20742 Phone: (301) 405-7555 Fax: (301) 314-9269 [log in to unmask] http://www.calce.umd.edu -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric Kalgren Sent: Wednesday, June 30, 2010 9:43 AM To: [log in to unmask] Subject: [TN] NTC - Solar Panels and small motors Once upon a time, in the early 90's, I bought a pith helmet with a solar powered fan attached to the front of it. It was hands-down the coolest hat on the block. The small solar panel that powered the thing broke and I want to replace it, but I don't know how much solar panel I need to run the motor. I know it's 3 VDC because it uses 2 X AA batteries as a back up supply, but I don't know how much current I need to run the motor. The old panel sat in a 2" X 2 1/2" pocket on top of the hat. I've Googled it and checked out a few options but nothing listed has the same footprint. And so I am punting to the TechNet to see if anyone might have an idea of how to guesstimate the current draw of a small DC fan without having an O-Scope handy. I'll send a picture to Steve as well, just for kicks. Thanks! Eric Kalgren Electrical Engineer The Ferrite Co. Inc. 165 Ledge Street Nashua, NH 03060 Phone 603-881-5234 X 153 Fax 603-881-5406 PRIVILEGED AND CONFIDENTIAL COMMUNICATION This E-mail is covered by the Electronic Communications Privacy Act, 18 U. S. C." 2510-2521 and is legally privileged. The information contained herein is confidential and is intended only for the use of the individual or entity named above. If the reader of this message is not the intended recipient, you are hereby notified that any dissemination, distribution or copying of this communication is strictly prohibited. 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