Revision as of 12:53, 22 December 2019

What it it?

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.
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.

Can 18650 cells really discharge at 10A rate? Yes! [1] - 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 - [2]. 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 - [3]

While specs say 250 cycles for 15A discharge - Multiple thousands of cycles are possible when charged to 80% and drained to 30%. - [5]

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.

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 - [12]

@@ Line 39: / Line 39: @@
 :*Cycle life and specs - [https://cdn.shopify.com/s/files/1/0674/3651/files/samsung-18650-30Q-spec-sheet.pdf?13304021761413850609] - 250 cycles to 70% of rated
 :*1000 cycles at 6A discharge rate bottoming at about 60% capacity for 2000 cycles? - [https://www.fasttech.com/forums/1686801/t/1238167/what-is-their-cycle-life/1]. So these last pretty long.
-*From lifetime design perspective, 2000 cycles is only 3 years, though. If used daily - batteries last only 3 years.
+*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.
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