Tesla 18650s and 21700s - Page 1
Forum section: electronics / general

author: OwO
author_rank: Super Contributor
timestamp: April 14, 2019, 04:36:50 pm
content: So I just recently discovered that there are quite a few sellers offering Tesla 18650 cells on taobao, and one listing even sells around 3000pcs/month. They are advertised as NCR18650B replacements with a lower ESR, and go for cheaper than the listings offering "genuine" NCR18650B. The Tesla cells go for around 13 yen (2 USD) whereas the Panasonic ones go for 20 yen (3 USD).I got a few (8 cells) to play with and do charge/discharge tests. There are no markings on the cell, allegedly they come without plastic wrapping originally and the green wrapper was retrofitted on. The charge capacity measured to be ~3250mAh and discharge capacity ~3150mAh. Variance between cells was low at around +/-50mAh. The charger reports an ESR of ~10mOhm when fully charged. During discharge I glanced at the cell voltage and mAh discharged so far once in a while, and compared to the NCR18650B datasheet. It seems the discharge profile is almost identical to the NCR18650B.There are also 21700 cells listed, I might play with those once I can get a charger that it will fit in. I do wonder how these sellers got their hands on the cells, or if they are actually pulls from Tesla battery packs.EDIT: Added photos

author: Nusa
author_rank: Super Contributor
timestamp: April 14, 2019, 07:13:58 pm
content: More likely they aren't Tesla batteries at all, even if they turned out to be fairly decent batteries in your tests.What do you see if you remove the green wrapper?

author: Kjelt
author_rank: Super Contributor
timestamp: April 14, 2019, 08:33:29 pm
content: Why not?Last week Tesla and Panasonic announced to withdraw their planned investment in their mutual LiIon factory, due to lower sales of cars than expected.They might sell their overstock, but they could be rejected batches also.

author: Nusa
author_rank: Super Contributor
timestamp: April 15, 2019, 12:51:36 am
content: Quote from: Kjelt on April 14, 2019, 08:33:29 pmNo labeling.Chinese vendor. Non-chinese battery brand manufactured only in the US (so far) and not sold directly (that I know of). That, by itself, generally means suspect fakes, bait-and-switch, or some other scheme until proved otherwise.Not expanding isn't the same thing as exceeding demand from their car and powerwall markets. I've seen zero indication of overstock from Telsa. Or availability of factory seconds. Have you?I'd look at Taobao if I was a Chinese reader, but I'm not. Google translate doesn't cut it there. The image posted by OP doesn't help me in the slightest.

author: digsys
author_rank: Unknown
timestamp: April 15, 2019, 01:06:02 am
content: Been down the same path - slowly working on our next Solar EV battery pack. May stick with pouch cells though -Same as you, dealings with Taobao have been sus, and VERY poor communications with the sellers. The cells I've tried "seem" to work, but there is NO WAYI can install them in a car unless I know EXACTLY where they are made, and get arealcertification. I've been following the 21700 news closely, buthaven't seen any "news" from 3rd parties or even Tesla yet. Watch and wait

author: OwO
author_rank: Super Contributor
timestamp: April 15, 2019, 02:33:00 am
content: Without the wrapper it's just a bare 18650 with a small QR code on it. The listings also show this.The question is if these aren't Tesla cells what are they? There are Chinese branded/unbranded 18650s of similar capacity but all go for a much higher price (only slightly cheaper than the Panasonic ones). This is actually the cheapest 18650 listing with >3000mAh and actually tested out to be >3000mAh. These also do actually have lower ESR than the genuine NCR18650Bs I have. My main suspect would be pulls from EV battery packs, but evidently not used ones because that would show in capacity tests.

author: sylvandb
author_rank: Newbie
timestamp: April 15, 2019, 02:41:22 am
content: Quote from: OwO on April 15, 2019, 02:33:00 amI doubt it would be possible to tear apart a pack without the cells showing some evidence of the former spot welds on the ends. (Maybe just some grinding marks?)sdb

author: OwO
author_rank: Super Contributor
timestamp: April 15, 2019, 02:42:54 am
content: Quote from: digsys on April 15, 2019, 01:06:02 amIf you aren't fluent in Chinese forget about buying from taobao. Stick with aliexpress, absolutely avoid ebay. The quality of stuff on taobao/aliexpress has improved quite a bit in recent years, now I see zero cases of false labeling of lithium batteries on taobao (most will use mWh instead of mAh to inflate the numbers but the numbers are still legit). There are still a few on aliexpress and much more on ebay. This is consistent with my experience of taobao > aliexpress > ebay. I would recommend getting a friend who actually knows the language if you want to buy anything from taobao.

author: OwO
author_rank: Super Contributor
timestamp: April 15, 2019, 02:53:32 am
content: Now, I simply care about getting decent and up-to-spec 18650s for the cheapest price, I don't give a rats ass where they are made or who is the CEO of the shell corp that owns the company who owns the factory. However these being fakes isn't very plausible because they could have commanded a higher price if they were sold under the Chinese brands or even NCR18650B. The listings for the Chinese cells indicate 15000 orders/month which is far higher than the Tesla listings, and with a higher price, so it would have been an easy sell.Quote from: sylvandb on April 15, 2019, 02:41:22 amI can't see any signs of welding or grinding, so maybe these aren't pulls. But then what are they?

author: sylvandb
author_rank: Newbie
timestamp: April 15, 2019, 03:40:44 am
content: Quote from: OwO on April 15, 2019, 02:53:32 amA mystery!They sound very nice. Please let us know if the cells start to lose capacity or evidence any other problems.