18650 Cells

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https://www.google.com/search?q=18650+cells&client=ubuntu&hs=KUs&source=univ&tbm=shop&tbo=u&sa=X&ved=0ahUKEwj8xPLHwdLfAhULtIMKHTQ3ADUQsxgIKw&biw=1438&bih=738

General Performance

  • 10A discharge, self-protection circuit inside.
  • 3.7V
  • 3 Ahr
  • 18 minutes of 37W
  • 10W for 1 hour
  • 30 of these give 1 kWhr
  • 45g each, so 1 kWhr weighs 1.5 kg.
  • At this density, ultra light cars (500 lb total) - will have 30 miles per kwhr.
  • 1kwhr ~ 4MJ - so about 1/10 kg gasoline. Given gas is 20% efficient in cars, we have 1/2 kg equivalent. Tbis gets us to about 240 mpg equivalent.
  • With 1 kW solar added- that gets us to about 400 mpg equivalent.

Specs

  • Note actual spec from a buyer on Amazon - [1]

Reviews

Management

  • While specs say 250 cycles for 15A discharge - Multiple thousands of cycles are possible when charged to 80% and drained to 30%. - [2]

Cost

  • From <$1 to $7 each - so choose wisely -
  • Cheapest - [3]
  • Best - Samsung 30Q - 3000 mAh - $3 in bulk - [4]
  • These appear to be on spec at 3000 mAh - [5].
  • Cycle life and specs - [6] - 250 cycles to 70% of rated
  • 1000 cycles at 6A discharge rate bottoming at about 60% capacity for 2000 cycles? - [7]. So these last pretty long.