Devices, Reviews, Test Equipment

ZKE EBC-A05 Premature Charge Termination Anomaly Workaround

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Last week I reported that I’d noticed an anomaly while running my new  ZKE EBC-AO5 through repeated tests using the cycle-test feature of its accompanying PC software. I’ve since identified the likely cause, along with a workaround, and I’m expecting a firmware fix soon from the manufacturer.

The problem can be seen in this chart.2015-2-12-10-14-45-EBC-A05

The charge phase is supposed to terminate when the current, shown in red, hits 0.12 A. Instead, it terminates at ~0.25A in the first cycle, and at ~0.5A in subsequent cycles.

I realized that the subsequent cycles were also terminating at about 90 minutes, which stood out, because I’d set a 90 minute timer for terminating the discharge phase if the voltage didn’t drop below a threshold first. A check of the raw data showed that the termination happened at ~88 minutes.

The device doesn’t allow a timer to be set during the charging phase, but I hypothesized that the timer from the previous discharge phase was somehow being utilized during the charging phase. I tried shortening and lengthening the discharge timer and found that, as I expected, it had a corresponding impact on the length of the charging cycle.

So, the workaround is to either omit the timer on the discharge phase, or set it to a duration larger than the time required to achieve a full charge for the cell under test. I’ve successfully run dozens of cycles now:

2015-2-19-11-2-0-EBC-A05

I also reported my findings to ZKE, using their published email address and received a reply thanking me for the report and letting me know that they would have an updated firmware by the end of the month.

Devices, Reviews, Test Equipment

ZKE EBC-A05 Cycle Testing Anomaly

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I didn’t do much with my ZKE EBC-A05 battery tester last week while I waited for a cheap, small used PC to arrive to run the EB Test software for long-term tests.

The computer came earlier this week, and after getting Windows patched up, I set up a test to run overnight that would cycle between charging to 4.3v and 0.12A, pausing, discharging at 2.4A to 2.75v, waiting 10 minutes for the cell to cool down, and then repeating the cycle.

When I checked on the progress this morning, everything looked good at first glance.

2015-2-12-10-14-45-EBC-A05Upon closer inspection though, I noticed that after the first charging cycle proceeded until 4.3v but terminated prematurely, at  0.25A current, and subsequent cycles cut of prematurely, at ~0.5A.

I tried stopping the test and restarting it again, and found that this time, the first charging cycle terminated at 0.5A.

I’ve powercycled the EBC-A05 and started a new testing cycle. So far, so good, the first charging cycle terminated at 0.12A, as desired. We’ll see if that holds for subsequent cycles.

I must say though, the fact that I’ve had this problem once makes me less enthusiastic about this device.  I was thinking of buying another 3, so I could run duplicate control and experimental runs of multi-day experiments at a time, but that only makes sense if these things are generally reliable.

USB Power Banks

5000 mAh Apple, I mean Millet, I mean Xiaomi USB Power Bank

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Finally received a new Apple USB Power Bank I ordered 3 weeks ago.

Did I say Apple?  I mean, Millet, no, sorry, Xiaomi. Sorry for the confusion, but in my defense, Xiaomi is borrowing so much of Apple’s design language, from the satin white packaging, to the specific grey of the logo and the “swiss” typeface, not to mention the particular tone and finish on the aluminum case.

I got the 5,000 mAh hour version from Banggood for $15.99, shipped. It took a three weeks to get here, but arrived in good condition. The footprint is about the size of my iPhone 6’s, but the powerbank is almost twice as thick.

It doesn’t quite achieve the fit-and-finish of an Apple product, but it definitely feels well made. That general level of quality is more than skin deep too.

The plastic trim pieces at either end of the case are secured with a few locking tabs and double-sided tape. It takes some delicacy but prying off the plastic trim on the bottom end reveals two phillips head screws. Removing them allows another plastic plate to be removed, which allows the core, holding the battery and the circuit board to slide out easily.

The PCB is populated with surface mount components, including a very nice, highly integrated BQ24195 IC from Texas Instruments that is well suited for power bank use. This chip does double-duty, providing both a buck-converter based lithium ion charger and a highly efficient boost-converter to provide the 5V necessary for USB devices from the battery. Both functions share the same shielded inductor, and operate at 1.5MHz, providing >90% efficiency during both charging and discharging. This efficiency makes the most of the power in the battery, but in doing so, it also reduces heat generation, allowing the pack to be charged at up to 2A. Discharge current is up to 2.1A. My brief testing bears out these numbers.

The power bank also has a thermistor, allowing the power IC to monitor the temperature of the cell during charge and reduce the charging current to prevent overheating. I’d guess it also uses the ICs ability to limit charging current draw based on USB coding from the input source.

This chip can be microprocessor controlled, and the microprocessor can set the charging voltage and current. I’m sure this comes in handy for Xiaomi, allowing them to swap in cells with different charge termination voltages without having to change components. Xiaomi also uses similar chips in their larger power banks.

I’m thinking of looking into getting ICs made up into small modules that can be incorporated into DIY projects. They support input voltages up to 17v, charging currents up to 4.5A. The boost-converter output current is apparently limited to 2.1A, but that’s still pretty good, and the IC can provide discharge protection at battery voltage at up to 6A sustained.

The pouch cell in my example comes from Lishen, but other teardowns have cells from ATL, which reviewers have conspicuously noted, also supplies cells to Apple.

I haven’t put this through a full cycle of use or tests, but based on the reports of others, I expect this to be a capable USB power bank.

Batteries, General

Test Results for LG INR18650-MJ1 3,500mAh 18650 Li-ion Battery

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Recently, there was news of LG’s first lithium nickel cobalt aluminum oxide chemistry cells. Panasonic has long led the market for 18650 Lithium Ion batteries with their own cells based on that chemistry. Their NCR18650B at 3,350 mAh capacity has been in wide availability for the last year, and some of their 3,600mAh NCR18650G’s have also popped up.

We now have reports of the highest capacity 3,500mAh INR18650-MJ1 version of LG’s new cells in the wild. If the real-world examples match LG’s claims, Panasonic will have some serious competition.

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Lucky for all of us, cooldiy_cn managed to get his hands on two of these cells and ran them through a series of tests which he posted on the Chinese Chongdiantou forum.

The weights of his two examples were 46.60g and 46.65g.

LG INR18650-MJ1 0.5C Discharge Curve

Above, you can see the test results with a 0.2C/0.7A discharge from 4.2v to 2.5v, which delivered 3,481 & 3,496 mAh.

INR18650-MJ1 3.5A discharge

At 1C/3.5A usable capacity is only diminished by about 1% and usable capacity remains good at higher discharge rates.

LG INR18650-MJ1 5A Discharge Test

At 5A, usable capacity is 3,390 and 3,393 mAh, or ~97% that delivered at 0.2C/0.7A.

LG INR18650-MJ1 10A Discharge

10A discharge is 3,252 and 3,310 mAh, or ~95% the usable capacity at a 0.2C/0.7A discharge.

He also tested the internal resistance of his two cells, and found that they were about 28mOhm (caveat that this can vary depending on method of measurement).

All in all, this is a promising development. I look forward to being able to buy these in new-old-stock and lightly used laptop packs, in a few years.

Devices, Test Equipment, Today's Mail

Today’s Mail: from Hong Kong, the ZKE EBC-A05

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Today’s mail brought a package from Hong Kong.

IMG_7256

Inside, was a ZKE EBC-A05.

IMG_7261
Whoops! This cell should be charged to 4.30v, not 4.35v.

 

This is a electronic load and charger for battery testing.

It can charge at up to 3A using a variety of charging voltages and profiles. For discharge testing, it can draw up to 5A @12v. There is a TTL-serial interface with a USB adapter and accompanying software for logging and controlling battery tests.

Update: I ‘ve posted a preliminary review, and I’ll be updating it as I go in the coming weeks.

Batteries, USB Power Banks

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

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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.

Batteries

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

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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:

 

 

Batteries

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

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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.