>A 65mm X 15mm X 5mm device ... Alternatively the spring could be >loaded with > 60 kg of charge by just standing on the thing. I'm not a >mechanical engineer or anything so I haven't done any sum's >on how much power could be generated from this but I get the feeling it'd be >able to keep up with a AA for a short period of time. The key thing to remember here (which I posted to Thad's wearables list a few years back in this connection) is that if you weigh 125 lbs all up and walk straight up a vertical cliff at 3 mph then you're putting out *exactly* one horsepower (33,000 ft.lb/min.), or approximately 750 watts. A 1350 mAH NiMH AA at an average voltage of 1.25 V holds 1.35 * 1.25 = 1.7 watt hours. So *if* you could charge an AA by walking vertically that fast it would take 1.7/750 hours or around 8 seconds. In that time you'd have walked 36 feet vertically. Although you can't charge an AA battery that fast, we now at least have figured out that 36 feet is how far your 125-lb weight needs to fall to charge it. So you just have to arrange for the 125 lbs (you or surrogate) to cover the 36 feet vertically slowly enough that the AA battery can absorb the charge without overheating. This of course scales, e.g. a weight of 250 lb only needs to fall 18 feet to charge your AA cell. Vaughan -- Subcription/unsubscription/info requests: send e-mail with subject of "subscribe", "unsubscribe", or "info" toWear-Hard Mailing List Archive (searchable): http://wearables.blu.org
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