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Need help with choosing battery and fan for air conned shirt instructable Answered

Hi, I'm new to this site and pretty electronically noob and very sleep deprived so please bare with me haha. I was looking at completing this project- an airconned shirt https://www.google.com.au/amp/www.instructables.com/id/air-conditioned-shirt/%3famp_page=true . But I didn't know whether I am buying the right fan for the project. It is a 12v 92mm fan with "2 pin?" which I'm looking at on eBay. I'm not sure how the "2 pin" will affect the wiring- can I still follow the instructions on the page withh this specific fan? https://m.ebay.com.au/itm?itemId=322787438856 And yes 92cm is my preferred size, just a little smaller than the 100mm one on the instructable page. And also, comments state that I can save money by buying a 9v battery, but the fan will just run a little slower. My fan is 92mm and goes 3500rpm which (comparing the size and rpm of other fans in my local electronic store) is quite fast. I'm assuming that using the 9v battery it will just run a bit slower. Is this accurate or will it also ruin the battery/fan's life expectancy, or drain much faster etc? Comments have stated that the batteries used in the instructable would only last a very short time (and batteries being expensive) so I thought to use rechargeable ones. Its going to be a gift for someone who works outdoors in construction in summer heat so it should at least be able to go for 9 hours before recharging. Ps. Any ideas on how to make it cooler via an ice container or cube without wetting the whole setup? Thank you heaps in advance!

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Akylanator (author)2018-02-16

Well it all depens on how mutch power the fan takes. If I was you, I would chek the powerconsumption with a multimeter, just measure how mutch amps it draws and then calculate the power. If you know how many amps it uses, you know witch battery to use. I would definitly use rechargeable batteries. For example, if it takes 0.250A and runs on 9V, it will consume 0.25*9= 2.25W. If you got a 9V, 5000mAh battery (it can give 5A for 1 hour). So it will last 5/0.25=20h. Hope this will help you somehow.

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JackieD56 (author)Akylanator2018-02-17

Thanks akylanator. I don't physically have the fans here and wanted to just ask for general advice and just buy bulk cause they'll take weeks to arrive. I understand your equation (and thanks for explaining it so well), but I assume the formula shows you which battery is most suitable. For example if the fan takes X amps, but is 12V, if I use a 9V rechargeable battery, can I calculate usage from that?

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