Test Report Summary: This cell is available with a lot of different battery wraps and top contacts, all salvaged from Tesla Model 3 vehicles. While the ones I tested were good performers there is no way to know the condition of any of the cells you buy and you use them at your own risk.
Here’s how BigBattery prepares the cells: https://youtu.be/ckhjYMAE9yg
Cell photos, discharge graphs, ratings graphic: Imgur: The magic of the Internet
This cell has recessed top contact that Tesla welds a cell-level fuse wire onto when they are used in a Tesla vehicle (see photos above). The companies that salvage these cells weld standard top contacts onto them and wrap them in various color wraps with different printing and ratings on them.
There has been concern that this recessed top contact could mean that these cells do not have the Current Interrupt Device (CID) that is in every cell made by the large manufacturers and hopefully every round cell we use. The CID is an important safety feature that shuts down the cell like a one-time circuit breaker if there is too much gas pressure building up inside due to misuse or mishandling. This can help keep the cell from bursting.
I took apart one of the cells I had and there appears to be a structure in the top contact structure of the cell (see the red arrows in the photos) that acts as a CID. But I cannot say for sure and I cannot guarantee that this cell will try to shut down if used too hard.
The cells I tested also have three tiny “stripes” in the bottom center that every Tesla Model 3 cell has and, AFAIK, no other cell has. I believe these marks are from the internal spot-welding of the tab of metal carrying current to the metal can from the spiral roll of materials inside the cell.
These Tesla cells equaled the performance of the Samsung 50E2/50E3 and Vapcell G50 (Samsung 50G rewrap). They performed a little better than the Molicel M50A and a lot better than the Samsung 50E and LG M50T.
The six cells I tested delivered from 4796mAh to 4888mAh and had a DC internal resistance ranging from 20.4mOhm to 22.9mOhm. This is not great consistency but these cells came from three different packs and their prior EV use (if any), storage time and conditions, and the quality of the top contact welding can affect their performance.
I estimate that these cells have a continuous current rating of about 10A to ensure decent cycle life and I rate them at 4800mAh. Like all of the ultra-high capacity 21700’s I recommend staying below about 7A (continuous or pulsed) to improve performance and minimize voltage sag.
Cells were donated for testing by Skyart (Battery Building Services by Skyart the skating duck - Battery Builds - esk8.news forums) and MrDrunkenMobster (https://www.duckbatterysystems.com) at the esk8.news forums. Thank you!
Ratings graphic: Imgur: The magic of the Internet
Full Test report: https://bit.ly/3ve5rz8
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These tests only note the ESTIMATED ratings for these batteries at the time I tested them. Any battery that is not a genuine Samsung, Sony, Murata, LG, Panasonic, Molicel, or Sanyo can change at any time! This is one of the hazards of using “rewrapped” batteries or batteries from other manufacturers so carefully research any battery you are considering using before purchasing.
Misusing or mishandling lithium-ion batteries can pose a SERIOUS RISK of personal injury or property damage. They are not meant to be used outside of a protected battery pack and you use them AT YOUR OWN RISK. Never exceed the battery’s continuous current rating and keep the plastic wrap and top insulating ring in perfect condition.
Any rating in my ratings tables can change at any time as different grade cells appear on the market, we get swamped with fakes, or new information becomes available to me. Please, never assume that the ratings in the tables are permanent and will never change! Always download the latest version before considering any cell purchase.
To see how other cells have tested check out this link: https://www.e-cigarette-forum.com/forum/blog-entry/list-of-battery-tests.7436/
