Teardown Updates: EasyAcc USB Powerbank, Dell TC03, and Tomo V8-4TOMO V8-4 / SOSHINE E3 DIY USB CHARGER / POWER BANK TEARDOWN

I’ve been busy doing teardowns over the past few weeks, and neglected to post links to them, so, before I finish up a few drafts I have in the works, here are links to what I’ve already published.

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:



UrJar and Re-Using Lithium Ion Batteries at the Bottom of the Pyramid

I started PowerCartel because I was interested in reusing lithium ion batteries, and I recognized that people in a variety of enthusiast communities with the same interest in li-ion reuse were missing opportunities to learn from eachother. As I thought more about the subject, I realized that there were also huge opportunities in developing markets, where labor was relatively cheap, and steady sources of electric power were hard to come by.

It wasn’t a surprise then when I came across a paper by researchers at IBM India on their pilot project to reused lithium batteries to provide economical lighting and power for poor citizens of India.

The paper, titled “UrJar: A Lighting Solution using Discarded Laptop Batteries” was authored by Vikas Chandan, Mohit Jain, Harshad Khadilkar, Zainul Charbiwala, Anupam Jain, Sunil Ghai, and Deva Seetharam of IBM Research India, and Rajesh Kunnath of Radio Studio. It makes a strong case for lithium battery reuse given the poor economics of recycling, makes an assessment of the yield of useful cells from discarded lithium battery packs, and describes the design and field testing of the UrJar.

The UrJar is a device powered with reclaimed lithium ion batteries. It provides power ports a LED light, and other devices like cell phones and/or a portable fan. There is circuitry to recharge the internal batteries, and provide the required power to the LED and external devices.

I’d challenge some of the design decisions in their prototype. They use a 3s2p (3 series, 2 parallel) topology for the cells, which requires proper cell management for safety, as well as longevity. The prototype omits this circuitry. Including it will impose an additional cost.  A 1s6p configuration would provide more safety in a simpler configuration. It would also allow a wider selection of inexpensive charging chips or even complete charging modules. The downside might be slightly lower efficiency in the circuitry to power external devices, but that could be offset by adding more cells, with the expense offset by the savings from commodified charging and power conversion modules. They might even be able to use existing commodity cases and electronics on the market for reusing 18650 batteries.

Its also worth considering that the laptop packs the source the cells from already have the circuitry to properly manage series packs by avoiding over-discharge of one bank, and balancing all of the banks during charging. There might be a viable approach to using the intact packs (when all the cells are of good quality), or reusing the circuit boards (when a working pack has to be assembled out of cells recovered from multiple packs).

I also have a quibble about their description of the Thinkpad battery packs used in their study. They describe them as 6 cell packs rated 85Wh each, and being at least three years old. This seems unlikely. The cells would have over 14Wh each, which works out to 3,800 mAh at 3.7v nominal cell voltage. 3,800 mAh 18650 cells weren’t available 3+ years ago. They aren’t even available today, so far as I know. Last I checked, the 3,400 mAh cells from Panasonic held the record.

These criticisms are all relatively minor though. The important issues aren’t the specifications of a prototype battery pack, or the  design and sourcing choices made for the hardware. What is important is that these batteries have residual economic value, and even more importantly, figuring out the right mix of cost, features and services for a product that will help poor Indian consumers better their lives, and stimulate local industry. On these fronts, the authors seem to have done good work. I also appreciate their bibliography, which will give me a head start on some literature research I planned to do. I’m in the process of drafting a letter to the authors, congratulating them on their good work, and inviting them to join the community I’m trying to start here around PackProbe, and other tools for reusing lithium ion battieries.

Their work has attracted plenty of other attention of late, I suspect the result of some savvy PR on someone’s part. IEEE Spectrum has a summary, as does the BBC News, and Technology Review.