18650 Cells: Difference between revisions
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*10W for 1 hour | *10W for 1 hour | ||
*100 of these give 1 kWhr | *100 of these give 1 kWhr | ||
*45g each, so 1 kWhr weighs 4.5 kg. | *'''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. | *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. | *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. | ||
Revision as of 16:04, 23 September 2020
What it it?
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
- https://thegunzone.com/best-18650-batteries/
- https://www.18650batterystore.com/Best-18650-Battery-Guide-s/142.htm
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
- ~$3 each in packs of 40 - [7]
Cost Analysis
- From <$1 to $7 each - so choose wisely -
- Cheapest - [8]
- Best - Samsung 30Q - 3000 mAh - $3 in bulk - [9]
- 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 - [13]
- See ratings link for 30A continuous
- 20A continuous and best seller- Samsung 25R 18650 - [14]
Links
- Ratings of 18650 batteries - [15]
- 18650 Cells
- Arduino Battery Chargers
- 18650 Battery Packs
- Battery Pack SMEs
External Links
- Fantastic forms for recycling old 18650s into DIY Power Walls https://secondlifestorage.com/index.php
- Best rated battery and everything you need to know about 18650s - [16]