18650 Cells: Difference between revisions

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=Sourcing=
=Sourcing=
*Samsung 30Q - $3.75 - [https://www.18650batterystore.com/Samsung-18650-p/samsung-30q.htm]
*Samsung 30Q - $3.75 - [https://www.18650batterystore.com/Samsung-18650-p/samsung-30q.htm]
*Sample - $1420 total with shipping for 400 batteries, 4 kWhr. May be relevant for a power cube application. [[File:epowercube.jpg|200px]]


=Cost Analysis=
=Cost Analysis=

Revision as of 16:17, 23 September 2020

What it it?

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
  • 100 of these give 1 kWhr
  • 45g each, so 1 kWhr weighs 4.5 kg.
  • 3 kWhr is under 15 kg, and costs $1000
  • 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.

Peak Performance

  • 20A continuous is common, and max at 40A continuous.
  • 20A continuous means higher peak for a short time - 40A. That is 150W per cell for a short time! Such as passing in automotive applications.
  • 100 of these give 15kW peak - for 5 kg of batteries. This is high power density
  • Each bat is $3, so for $900 you get 45kW peak power - sufficient for excellent performance on hybrid vehicles that have a small engine (5kW) and have much higher peak power for hills and passing (50kW).
  • Solar cars as such become practical, with solar hydrogen power.

Best Cell

  • Samsung 25R - [1]. 20A continuous for 6 minutes at 3V. 60W cell. 100 of these are 6 kW, which make for a decent burst power source at 4.5 kg weight.
  • Practical and affordable scenario - 12kW - 6 minutes of time at a weight cost of 9kg. $560. As part of an auxiliary hybrid drive train.
  • Changfa Diesel costs 180kg in weight - so is much heavier.

Discharge Characteristics

  • Can 18650 cells really discharge at 10A rate? Yes! [2] - Panasonic goes up to 20 amp rate. 6S (6 cell) packs are 22v. 10 of 6s cells, if discharged at 20A, give a 200A welder for 6 minutes. See Discharge Rate.
  • Crappy ones can be as low as delivering 2.5A each - [3]. With 100 of these, that's still a 250A welder which has a weight of 5 kg for the batteries. Still impressive.
  • Discharge rate of 20A yields temp increase to 50C - [4]

Specs

  • Note actual spec from a buyer on Amazon - [5]

Reviews

Management

  • While specs say 250 cycles for 15A discharge - Multiple thousands of cycles are possible when charged to 80% and drained to 30%. - [6]

Sourcing

  • Samsung 30Q - $3.75 - [7]
  • Sample - $1420 total with shipping for 400 batteries, 4 kWhr. May be relevant for a power cube application.
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Cost Analysis

  • From <$1 to $7 each - so choose wisely -
  • Best - Samsung 30Q - 3000 mAh - $3 in bulk - [8]
  • These appear to be on spec at 3000 mAh - [9].
  • Cycle life and specs - [10] - 250 cycles to 70% of rated
  • 1000 cycles at 6A discharge rate bottoming at about 60% capacity for 2000 cycles? - [11]. So these last pretty long.
  • From lifetime design perspective, 2000 cycles is only 3 years, though. If used daily - batteries last only 3 years. In practice - 10 year max is likely. Not a good solution environmentally.

20A Continuous

  • This one says it's 20A continuous - [12]
  • See ratings link for 30A continuous
  • 20A continuous and best seller- Samsung 25R 18650 - [13]

Links

External Links