Tag Archives: 18650

Used Tesla 444 cell 6s74p Modules for Sale

Last night, a new member on the EEVBlog forums posted that he had  ten battery modules from a Tesla Model S for sale. The asking price? $1,900 each, shipped within the US.

According to the poster, it is a rev b pack from a car with ~4,000 miles on it. Each module has 444 18650 cells, configured as six in series, 74 in parallel (6S74P). Capacity is 233Ah and 5.3 kWh. Each module has its own Tesla BMS (battery management system), and plumbing for heating/cooling.

I also found another thread about the same modules in in a DIY electric vehicle forum. There is more discussion there, including some testing results by one of his collaborators. And here is a thread on another EV forum where the collaborator posted earlier in the month about hunting down the source pack and break down some of the modules into cells for sale.

Doing a little math, this works out to $4.28/cell, $0.12/Ah and $2.78/Wh. Back in November, I came across a Hack-a-Day interview with the first person I know of to publish a Tesla Model S pack teardown. I noted that he’d paid ~$20 for his pack, which worked out to about $3/cell, so, this is ~40% more expensive/unit, but with the advantage of 1/10th the initial outlay.

The cells in these Tesla packs are a variant of the Panasonic NCR18650 cells. The exact variant isn’t known, and is probably Tesla-specific, but there are NCR18650 cells with similar capacity on the market. Like all 18650 Li-ion batteries, any NCR18650 cells available retail, or in smaller wholesale quantities have passed through a few middle-men, making the wholesale prices hard to estimate. What I do know though is that it is hard to find such cells for less than $6.50. Laptop packs with 9 similar cells are over $100 new, though you can generally find surplus packs for $50 or $5.50/cell. With only 4,000 miles on the battery pack, and given that Tesla treats them pretty gently, the cells in these packs are going to be pretty close to new condition.

Given all this, these modules seem like a reasonable price if you can use the entire module intact.

On the other hand, using cells from these packs individually probably doesn’t make sense. In addition to the effort required to disassemble the module, these cells may need to be wrapped. It is also quite possible that these cells don’t have some of the safety features people expect with 18650 cells, since the pack has other provisions for dealing with cell shorts and overheating.

If you buy any of these modules, I’d be interested to hear about your plans for them. If you’ve seen other Tesla modules for sale, I’d appreciate a link, or information about the pricing.

New LG INR18650 MH1 (LGDBM1865) 3,200 mAh 4.2v!

I was taking advantage of Google Translate to skim through recent posts on a Chinese battery/power bank/charger blog. They have a lot of posts on new high-capacity cells from various chinese battery manufacturers, but post on a new cell from LG caught my eye.

I haven’t been keeping a on the latest developments in lithium ion batteries because I’ve been focusing on recycling cells from old laptop packs, and I have my hands full just keeping up with all the variants that were in new packs in 3-6 years ago. Still, the INR18650 MH1 (LGDBM1865) grabbed my interest because its 3,200 mAh capacity and 10A (>3c) discharge rate struck me as unusual.

The capacity itself isn’t revolutionary, Panasonic has had a 3,400 mAh cell on the market for a while, and Samsung and LG have both had 3,200 mAh cells on the market for over a year. The existing Samsung and LG cells have a maximum discharge rate of 1.5C (1.5x rated capacity), or ~4.6A, and the Panasonic seems to allow 2C/7.8A  discharges, wheras this cell is rated at 10A, or more than 3C.

It has another interesting characteristic, a 4.2v charge termination voltage, instead of the 4.35v of many existing high capacity cells. Many lithium ion chargers, and most cheap charging ICs/modules have a fixed 4.2v charge termination voltage. Charging high-capacity 4.35v cells to 4.2v doesn’t harm them, and can actually extend their lifetime, but leaves 10-15% of their capacity unused. On the other hand, when the INR18650 MH1 is charged in a 4.2v charger, all its capacity is utilized.

Of course, the 4.2v voltage also brings a tradeoff. The nominal voltage is 3.67v, vs the 3.75v of LG’s 4.35v 3,200 mAh battery. This results in a somewhat lower power capacity of 11.7Wh vs 12Wh, or 2.5%, but that’s much less than the 10-15% lost when undercharging a 4.35v cell.

I’m not sure how I missed it, but it looks like user cooldiy_cn managed to get his(?) hands on some and has posted test results for the INR18650MH1.

Some added details, and highlights of the tests:

  • In addition to this 3,200mAh cell, LG is bringing out a family of INR cells with a range of capacities, including:
    • 2,800 mAh: INR18650MG1
    • 2,900 mAh: INR18650M
    • 3,500! mAh: INR18650MJ1
  • The INR18650MH1 specifies a 1C fast-charge rate
  • Measured internal resistance of the tested samplesL 34.2 and 36.2 mOhms.
  • 0.2C/0.62A discharge tests at 3,217 and 3,214 mAh
    • Cooldiy_cn claims the discharge curve is very similar to the Panasonic NCR cells.
  • 1C discharge tests yield 3,109 mAh and 3085 mAh for the tested cells.
  • 10A discharge test of one cell yields 3,253 mAh. It maintains voltage well enough to deliver 10.39Wh.
    • The NCR18650 BD 10A can deliver 10A, though it is out of spec. When it does, it only delivers 2,831 mAh, and the voltage sags so much that the power delivered is only 8.856 Wh.

If you want to see the discharge graphs, check out cooldiy_cn’s original post.

More info: