Laptop external power from batteries (DC/DC)

VirginSnow at vfemail.net VirginSnow at vfemail.net
Wed Aug 20 22:05:08 EDT 2008


> From: Bill McGonigle <bill at bfccomputing.com>
> Date: Wed, 20 Aug 2008 20:03:27 -0400

> in series.  So, if one bought two marine batteries, a bigger box, and  
> was familiar with proper acid handling techniques, ought there be an  
> electrical reason that 'just' making a 19.5v battery with the  
> required number of cells would be insufficient to power a laptop  

A lemon with zinc and copper electrodes generates ~1 VDC.  Stringing
20 lemons in series would give you ~20V.  Each string of 20 lemons
would provide about 2mA of power, so wiring 45,000 of these 20-lemon
batteries in parallel would generate the 90W required to power Ben's
laptop.

In theory, all you would need is 900,000 lemons, 900,000 zinc nails,
900,000 pennies, and 90,038 copper interconnects.  Assuming a lemon
costs $0.25, a battery containing 900,000 lemons would cost $234,000.
Yeah, that's kind of pricey for a SFD demo.  But if we gave the
wholesaler an Ubuntu disk, we might be able to talk him into giving us
a discount.


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