Category Archives: Batteries

GBatteries and their BatteryOS and BatteryBox

Today, I’m going to look at GBatteries, a startup incubated at YCombinator in 2014 that is now based in Ottawa. Their first consumer product, BatteryBox, was launched on Kickstarter last year, and as of January 2015, they were shipping. BatteryBox is a 60Wh (~14,000 mAh @ 3.7v) backup battery pack for Apple MacBooks and USB powered devices.

Last summer, I decided to dig into the subject of lithium ion battery reuse. Tomorrow’s used batteries are today’s new batteries, so I’ve been learning what I can about what today and tomorrow hold for new batteries. Its really too much for one person to go into in great depth, but I’m still trying to get a better lay of the land, and part of that effort is looking at battery-related startups like GBatteries.

If you visit the GBatteries site, the first thing you see isn’t the BatteryBox, instead you see a plug for “BatteryOS” their new battery management system that “increases battery capacity and cycle count.” It goes on to say:

BatteryOS is a new way of controlling rechargeable lithium-ion batteries that enables any normal battery to have higher capacity and not degrade over time.

It’s clear then that BatteryBox is an application of their new technology, a way to prove the value of BatteryOS value while bringing in some revenue, with he longer term goal of licensing technology and/or selling components that device makers will incorporate into their own products.

Digging in a little deeper, we find that GBatteries gets more specific about the claims about BatteryOS:

 10-40% more capacity (varies between specific type of li-ion chemistry), have a 4x higher cycle count, and not degrade in capacity over time.

In considering these claims, it helps to understand a bit about industry standard approaches to lithium ion battery design and management. To start, lets define key factors:

  • Energy capacity / density
  • Power delivery
  • Lifetime
  • Safety
  • Cost

These factors are all, to some degree, interdependent, which allows designers to trade them off aginst each other. For portable consumer electronics devices, like phones and laptops, the working range fall into a relatively narrow space.

Within that space, one tradeoff designers make is energy capacity vs cell lifetime. A simple choice offered to designers is to sacrifice ~10% of the overall energy capacity of a battery in exchange for a doubling of its lifetime. This is usually accomplished by limiting the maximum voltage allows when charging, and the minimum voltage when discharging.

With this background, we start to understand how BatteryOS might deliver on its promises:

  • 10-40% more capacity (varies between specific type of li-ion chemistry)
  • 4x higher cycle count
  • not degrade in capacity over time

What they seem to be saying is that a device designer can have their cake and eat it to. Rather than giving up capacity for lifespan, or trading lifespan for capacity, they can have it all, and more.

Gbatteries claims that they have patents pending, but despite starting the company in 2012, and participating in YCombinator a year ago, I can’t find any relevant patents for father and son co-founders Tim and Nick Sherstyuk, so it is hard for me to evaluate their claims in more detail.

The BatteryBox would seem to be a chance to test these claims. They’ve been shipping them out to Kickstarter supporters for the past few months, but so far, I haven’t been able to find any independent tests and I’m not in a hurry to buy one and reverse engineer it.

We can, however, evaluate the published claims about BatteryBox BatteryOS, and other products and see if everything makes sense.

Salient details about BatteryBox:

  • $219 price ($129 to kickstarter backers)
  • 60Wh from 5 pouch cells
  • 49x95x63mm
  • 404g

Lets start with the price. There are a number of external battery packs available for laptops, but only a handful that work with the MagSafe connector on Mac laptops.

Hyperjuice sells a 360g, 60Wh battery pack that works with Macs for $199 that includes a DIY kit to adapt your existing MagSafe cable, for $249, you can get one with an already modified MagSafe adapter.

Voltaic Systems sells a 72Wh pack for $129, and a modified MagSafe cable for $20. It weighs 558g.

Both HyperJuice and Voltaic are bundling a MagSafe connector with rebranded external battery packs designed and manufactured by someone else, and similar packs are available from other brands as well, such as this $99 Anker-branded version of the same 72Wh pack Voltaic is selling.

Adapting MagSafe cables isn’t officially sanctioned by Apple, but clearly, HyperJuice and Voltaic have been willing to take the risk, and seem to have achieved some success over the years. For some reason though, Gbatteries decided to go another route with BatteryBox, developing a non-magnetic, MagSafe compatible connector that clips on to the side of the laptop.

I don’t know why Gbatteries decided to take this route. It may be the risk-intolerance of their funders, or perhaps they want to avoid antagonizing Apple because they hope to sign them up as a BatteryOS customer in the future.  The advantages to consumers over a $20 MagSafe cable from Ebay aren’t apparent.

What is obvious is that for 55% the price of the BatteryBox, one can get a $20 cable and a $99 Anker pack with 20% more initial capacity.   The Anker pack is also 20% heavier, but its thin form-factor makes it easier to tuck into a laptop bag than the BatteryBox.

From a cost, capacity and density point of view then, BatteryBox’s use of BatteryOS doesn’t provide obvious benefits over the status quo at time of purchase. Of course, that’s not everything it promises.

The other benefit BatteryOS is supposed to provide BatteryBox users is a 4x longer lifespan. Lithium ion batteries wear out due to a combination of time and use. That wear generally shows itself in a few different ways: increased internal resistance, decreased charge/discharge rates, and decreased capacity. In ordinary use, the decline is gradual and continuous, every charge discharge cycle results in a tiny bit of wear.

GBatteries is rather inconsistent in the way it talks about the battery lifetime benefits of BatteryOS. In one sentence, they claim both 4x the cycle count AND that the capacity won’t degrade over  time. And yet, they also show a graph of runtime vs use that shows that the capacity of cells in BatteryBox decline noticeably over time, though at a lower rate than cells managed by traditional means.  Its also worth noting that the graphs they show don’t start the Y axis at 0, which exaggerates the differences between the alternative management techniques.

In the long run though, it seems that the 20% capacity advantage and the almost 2x cost advantage of the non-battery-box solution goes a long way to offsetting the purported advantages BatteryOS brings to the BatteryBox.

Looking closely BatteryBox does help clarify some of the claims about BatteryOS. GBatteries claims significant capacity AND cycle-life benefits from BatteryOS. BatteryBox makes claims about significant cycle-life benefits, but the capacity tracks closely with that of other devices with the same weight, suggesting that the claims for BatteryOS don’t make the remaining tradeoffs clear.

While BatteryOS isn’t enough to make BatteryBox a compelling product, and while it may not provide all the benefits claimed, at least not at the same time, it might still be an important improvement to battery management, and provide a compelling benefit when incorporated into new versions of existing products.

Even so, I think GBatteries and BatteryOS face an uphill battle, because it isn’t clear to me that they bring anything new or unique to the table.

The lithium ion battery market was long dominated by the needs of consumer electronics devices like laptops, cameras, and mobile phones. The overall pace of progress in these product areas has been rapid, which drives relatively short upgrade cycles (2-5 years). When lithium ion batteries became durable enough to go mainstream, device manufacturers expected them to be replaced once or twice over the lifetime of the product. Since then, capacity improvements have been given at least equal weight with durability advances. Durability has improved enough that they are now expected to last the lifetime of the product they power, shifting even more emphasis to capacity improvements.

In this era, anyone needing greater durability often found it made more sense to work with cells from the consumer electronics market trading a bit of their superior capacity and cost for better durability.

This is exactly what Tesla did when designing the Tesla Roadster, which used 18650 batteries designed for laptops. Along the way, they developed their own techniques for better extending battery lifespan. In addition to the well-worn technique of limiting charging and discharge voltages to trade some capacity for durability, they also use a new charging profile. The traditional charging profile for LiIon batteries is to use a constant current (often the current required to fill the battery in 2 hours) to charge the cell to the voltage limit (typically 4.2-4.35v, depending on cell chemistry), and then hold the voltage constant until the current has drops to some predetermined threshold (often 1/10th the initial charge rate).

Tesla’s approach is to add another charging stage at the beginning of charge. This charging phase uses constant power, up to a voltage level below the final charging voltage target. This results in a decline in charging current as cell voltage climbs. This helps reduce heat generation at higher cell voltages, avoiding the combination of conditions that lead to the fastest cell wear. Once a threshold voltage is reached, charging switches to constant current to the final cell voltage which is then held until the current declines to its cutoff threshold. I expect that other companies have developed their own novel battery management schemes.

Of course, it doesn’t mean that GBatteries doesn’t bring something more to the table, but its also worth keeping in mind that some of the advantages they bring might be either offset or reduced by improvements in other areas. The most obvious is improvements in that batteries themselves. As I explained above, Tesla started by using cells from the consumer electronics industry for the Roadster.

For the Model S, they worked with Panasonic, their battery supplier, to design a cell for automotive use. It should be obvious that automobiles have longer lifetimes than consumer electronics by a, and that electric cars need to prove that their batteries will meet expectations set by existing automobiles. One obvious improvement for vehicle batteries then, is durability. In addition, cost and capacity will remain important considerations. The result I think, is that applications that need more durability than available from consumer electronics cells will now have the option of working with cells developed for the automotive market.

In the end though, the market for Lithium Ion batteries is so large already, and will quickly grow even larger, that an innovation that can offer a 10% improvement to 10% of the market could be very valuable. Whether or not BatteryBox was a good first step is in doubt. It targets a small portion of the overall market. It isn’t a compelling product in its own right, which makes it less compelling in demonstrating the value of BatteryOS.  On the other hand, the experience they gained in developing and selling BatteryBox will probably help them better understand the issues that device makers, the potential customers for BatteryOS, deal with.




Notes on JB Straubel’s Keynote at the 2014 SEEDZ Energy Storage Symposium

I thought I’d share my crude notes on a very interesting talk about energy storage from Tesla CTO JB Straubel. The slides are available as a PDF.

  • JB Straubel Keynote
    • CTO, Tesla
    • Previously CTO & co-founder of Volcom, specializing in high-altitude electric aircraft platforms
    • Board Member, Solar City
  • Why is Tesla Deeply invovled in Energy Storage
    • EV Battery History
      • Status quo was led-acid in 1995
        • Stagnant performance
      • LiIon made possible Tesla and the rebirth of EVs
        • 4x gravimetric energy density
        • 6x volumentric energy density
        • 2x cycle life
      • Tesla was first to do Li-ion R&D for vehicles in 2003
    • Tesla Roadster 2008
      • Sought to challenge internal combustion vehicles on more than just fuel economy
      • ~2,500 sold
      • Largest battery pack in a vehicle
        • 50kWh +
      • Optimism based on progress of LiIon cells
        • ~2x improvement in energy storage capability of batteries in the decade between EV1 era and the Tesla Roadster
          • 300Wh/litr to 600Wh/litre
          • Accompanying weight reduction as well
        • In talking to companies involved in 2005, they saw no reason for progress to plateau
        • Ten years later, they expect progress to continue for the foreseeable future.
        • 40% improvement between introduction of the Roadster and the Model S
          • ~300 miles range
          • 85kWh
          • Smaller pack than the roadster
        • See this trend continuing for the next 10-20 years
        • Only 10-20% away from being able to compete broadly with the internal combustion engine.
    • Long term goal is to sell millions of cars
      • Energy storage is the biggest factor influencing cost, and therefore, volume.
    • Current offerings
      • Roadster
      • Model S
        • Main focus
      • OEM
        • Toyota RAV 4
        • Mercedes-Benz
          • BClass
    • Model S Battery Pack
      • Scale & Scope have enabled a cost point that is competitive in other markets outside cars
      • Utilities
      • Energy density is a key path to lower cost
        • Automobiles
          • Not intuitive
          • Some automobile manufacturers have tried to cut energy to cut costs.
        • 200Wh/Kg
        • Benefits for stationary storage
          • smaller footprint
          • easier retrofit
      • Current costs and projections are on track
      • Manufacturing volume is important too.
        • Goal to build 500,000 Gen3 vehicles/year
          • using capacity in existing Bay Area Plant
        • Energy storage required to meet that goal is another story
        • In 2013 ~34 GWh of lithium ion batteries were manufactured, but from ~21 GWh in 2010.
        • Tesla’s projects to use 3-4GWh in 2014
          • Approximately 10% of WW volume
        • 500,000 Gen3 vehicles/year will require 10x current, or ~35GWh of batteries in 2020.
        • Gigafactory sized to meet that demand
          • Would still only supply 0.5% of WW new car market.
          • Doubling WW capacity
          • Reengineering supply chain with major opportunity for cost cutting
          • 30% cost reduction by 2017 ramp-up
        • Thinks that the market for non-automotive storage will grow even faster than the electric car market.
          • Grid storage is slow to mature, but once you cross certain price thresholds, it becomes a commodity market that sells on cost savings
        • Approach to cost reductions at the gigafactory
          • Looking at everything, including the sourcing of the raw materials.
          • Materials are a meaningful portion of the cost of cells
          • Plan to use their purchasing power to use demand as leverage for sustainable practices throughout the supply chain (labor practices, energy, etc)
        • Gigafactory
          • 35GWh of cells
          • 50GWh of packs
            • 15GWh for stationary packs
              • 10x of the California mandate
  • Tesla and Stationary Storage
    • ~2012 adapted vehicle pack architecture for residential energy storage packs
      • 5kW/10kWh
      • Originally targeted at people with solar and teslas
      • Slow to scale
        • ~1000 systems
      • People who wanted to play with energy in their house
        • Peak demand management
        • “Islanding” to isolate their system from grid and allow operation in the event of a power outage
      • Experiment with aggregation of systems
        • Coordinated across households
        • Business models are a challenge
    • New experiment is a larger-scale system
      • Module
        • Based on model S pack architecture
          • Different arrangement of modules
          •  Same cooling and management
        •  Two hour-rate pack.
          • 200kW / 400 kWh+
        • “Single skid” unit
        • Roughly the size of a shipping pallet
        • 800Kg
      • Pilot deployment
        • SuperCharger location
          • Big enough to be worth the time
          • Very peaky load
            • Up to 250KWh peak demand from cars
            • <100KW peak from meter
      • Thinks that utility side opportunities are significant
        • Backup power
        • Demand management
        • Scale up of renewables
          • This will be the major driver for storage!
        • Major adjustments needed in rate structures/incentives
        • es- I wonder where trends in peak generation costs vs storage costs cross
      • Large Pilot (2013)
        • “One of the bigger installations”
          • Tesla’s Fremont plant
          • 1MW / 5 modules
          • Manages ~10% of peak demand
          • 100 MW substation with 100kV tie.
          • 1-2% of installed grid-attatched storage
          • In the process of doubling capacity
  • Thinks of Tesla is an energy innovation company, more than a car company.
  • Cautionary note about building for economic sustainability, avoiding dependency on incentive programs
  • Innovation needed in storage management technology and relationship to grid and generation
  • “The stone age came to an end not for lack of stones, and the oil age will come to an end not for lack of oil”
  • Thinks the economics of renewables are already compelling and now constrained by storage
  • Q&A
    • Can the world support the scale up from a primary resource point of view
      • Li-ion are primarily graphite/carbon for anode, nickle for the cathode (for their chemistry). Steel for can, polymers for separators, organics for electrolytes
      • Predictions of shortages of lithium aren’t well founded
      • Thinks there is a bubble in lithium prices, but Li-ion costs aren’t the major contributor to lithium cell costs
    • Have you thought about the policy changes needed to drive this change?
      • They have been building relationships with CPUCs and utities and even state and fed regulators, but it isn’t a big focus.
      • Tesla is an innovation company that focuses on creating products that drive the need for regulatory changes.
      • Utilities are conservative. Automotive experience is demonstrating that this technology is ready for utility use.
    • Recyclability of lithium ion batteries
      • Recycling is being built into the Gigafactory. With enough volume there are great opportunities for materials reuse.
      • Challenge now is that growth is so steep that the volume of cells coming back is so much lower than current production
    • What is the commercial lifespan of Lithium Ion batteries?
      • Lithium ion batteries for the next 5-10 years
      • Not waiting for the next big thing…
      • Lithium ion cells make business sense now, which is why they investing.
      • Looking historically, improvements aren’t necessarily revolutionary.
        • Often it is through incremental improvements to components of the system that can leverage a lot of existing infrastructure for building cells and packs
          • Better cathodes
          • Better electrolyte
          • Better separators
        • Thinks we can double energy densities with better anode and cathode materials over the next 10 years.
    • 18650 vs other formats
      • Thinks people are hung up on form-factor for no good reason
      • At the scale they are dealing in what matters is whats inside.
      • What matters
        • Cost of materials
        • Thermal / Safety parameters
      • Their conclusion is that relatively smaller form factor are a reasonable optimization tradeoff between safety, thermal and cost.
        • Slightly larger than an 18650
        • Cylindrical makes sense from a cost perspective
      • Some applications will have different characteristics
      • Large cells just move complexity inside the cell
    • Deployment plan and pricing metrics for fixed storage
      • Depends on market
        • Residential
          • Leased to customer, bundled with larger offering
        • Mid-market commercial customers
          • Many prefer to buy outright
          • Others want Tesla to provide savings, take care of utility interconnect, etc
          • Some people don’t want to arbitrage their energy
            • He did it at his for a while. Got bored with it
          • Thinks at the end of day, Tesla or a 3rd-party financing company will end up owning most of the packs and be responsible for management
        • Utilities are another matter, given the scale and dollars involved.
    • Have you developed a center to deal with dispatch of modules?
      • They are building it.
    • Failure rate and warranty for modules
      • Quite reliable
      • Automotive application is much harsher
      • Maybe over-engineered for fixed application
      • Warranty rates are great
    • Degradation profile
      • Similar to cars
      • Optimized for 10 year life
      • Avoid paying too much for a product that outlasts the product, or the pack.
    • What are your perspectives on the power converter, are you building it yourself?
      • System design and integration are their major focus, just as with automobiles.
      • The power electronics for Tesla Model S is a very capable starting point for these fixed storage modules.
      • Costs for the power electronics are dropping quickly, will see less than $0.10W very quickly.

Apple’s Batteries, Apple Cars?

Earlier this year, a series of rumors and reports emerged that Apple may (or may not) be making serious investments in developing an electric vehicle. Taken as a whole, the rumors and reports are intriguing, if not convincing, but there are also plenty of alternative explanations for the circumstantial evidence.

This isn’t a site about Apple though, or cars, or technology in general, it is about batteries, and my purpose with this post is to note some interesting tidbits about Apple and batteries that have emerged in the attention to the Apple Car.

First, Apple has been recruiting people from battery companies. They are being sued by A123 for hiring some of their employees. A123 is a battery company specializing in Lithium Iron Phosphate (AKA LiFePO) cells. The employees in question were A123’s former CTO, Mujeeb Ijaz, and various engineers responsible for developing and testing lithium ion batteries. A123’s earliest design wins were in batteries for tool packs, but there current focus is squarely on providing batteries for the growing electrical vehicle market. They also faced bankruptcy recently, so it is not surprising that their employees were open to be recruited to working on battery technology at Apple, whether or not those batteries will be used in electric cars.

In the complaint, A123 claims that Apple has hired employees from other li-ion battery companies A123 has ties to, including SiNode Systems, Samsung, Toshiba, LG, and Panasonic.

Apple is clearly interested in advancing the state of the art for battieries in service of its publicly known product lines. The design of the upcoming Apple Watch seems strongly influenced by the issue of battery life and the new MacBook goes to extraordinary lengths to maximize the volume of the device occupied by the battery.

This isn’t anything new for Apple, but they’ve gone to extraordinary lengths with the new MacBook.  Apple used to use battery packs built around the cylindrical, metal encased, 18650 cell, but about 10 years ago, they were pioneers in the use of pouch cells, which use a plastic pouch, rather than a metal can, and are shallow rectangles, rather than cylindrical. Apple’s move to pouch cells allowed thinner systems with less space wasted in the baps between cells. The followed up by forgoing field-replaceable batteries, for battery packs installed in the main cavity of the computer. The space saved was used to increase battery capacity. The Retina Macbook Pro went even further, gluing the cells directly to the laptop case. It also used a mix of cell sizes.

The latest MacBook goes even further. The logic board is tiny compared both to past Apple laptops, and the batteries, which occupy most of the volume and floor-plan of the computer, are unprecedented. The cells aren’t simple rectangles, they have rounded and notched edges.

Screen Shot 2015-03-17 at 3.36.43 PM

For even more battery density, they are stacked in a terraced fashion.

Screen Shot 2015-03-17 at 3.36.51 PM

Whether an Apple car makes it to market, if it is being developed at all, I am certain that Apple wants to stay on the cutting edge of battery development, whether in packaging, chemistry, management or manufacturing. Whether it is Apple, or its suppliers in the lead, Apple needs people who know all about the development, manufacture, and use of lithium ion batteries. It is no surprise they’ve been hiring them.


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

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.


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.

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.

Dell XX326 11.1V 60Wh Battery Pack Teardown

I picked up a lot of ten Dell XX326 6-cell 60Wh battery packs from an eBay seller for about $4.50/pack. The seller described them as untested surplus, and based on the presence of unworn external labels in the photos on the listing, I thought they might be unused packs and hoped I could turn around and sell them individually for a profit.

IMG_6762 IMG_6761

No such luck. The packs had more physical wear than I expected. When I hooked them up to PackProbe, I only got data out of two of them without hassle and the data they provided seemed to have problems, for example, reporting design capacity as 0. With a little work, I got one more to spill its secrets. A couple more would ACK a query at their address, but that was it, and the rest gave nothing at all.

I decided to tear apart a few of them. When I got one of them open and measured with a multimeter, I found all the cells were flat, 0V. The next one was a little better, but not great.IMG_6764

3.18V, for 3 banks in series. Not looking good. Lets see what the individual banks registered.

IMG_6765Hmm, one bank measures 2.86V. That’s not bad. The other two banks must be junk though, with a combined voltage of less than 0.4V.


Wait a second, 3.0V that’s not bad, hmmm…


Yikes!!! One bank of cells has reversed polarity, in a really big way. I double checked my connections, but I still got the same result, -2.69V!

I tore into another 6 packs. One was nearly flat, with each bank just over 0v. The rest had at least one bank of cells at a reasonable voltage, with the remaining cells being low, flat, or slightly reversed.

It looks like all the packs are ~4-5 years old, and the packs I could get data out of each reported less than 40 cycles. I have to wonder what happened to these packs that they are in such crummy shape, or if the problem is with the pack design/engineering. There are also some manufacturing issues, I think two of the packs had welds break loose, without tearing the nickel conductor strips.

After pulling the individual cells out of three of the packs I’ve opened I’m even more baffled. All of them had at least one cell with failed spot welds. The first pack had all 0v cells, as expected. The second I thought would have two good cells, but it turned out only one cell in the bank was good. The other was flat. The third I thought had two good banks, but once the cells were separated, only one in each of those pairs was good. I think bad connections may have played some role in cell failures.

One theory: Cells paired with poorly connected cells failed because they were overused. I also wonder if some cells may have broken internal connections.

I’m holding off ripping apart the rest of the packs I’ve already opened, because I’m curious if I can get the battery management circuit to give up some data.


Notes from “Why do Li-ion Batteries Die” Lecture

Interesting video of a lecture by Dr. Jeff Dahn, professor of Physics and Chemistry at Dalhousie University in Canada on what causes lithium ion batteries to deteriorate, and how the situation can be improved. Dahn was involved in development of lithium ion battery technology, and maintains an large, active research program devoted to studying materials for batteries and fuel cells.

The video is over an hour long, and the pace is a little slow. I’ll be updating the post with my notes as I go through it.


  • Manufacturer testing and rating of battery lifetime uses a simple cycle test that takes place under a compressed timeframe, with unfortunate results.
    • Charge/discharge cycles are done back-to-back, at charge/discharge rates that might not mirror real-world use.
    • This underrepresent the impact of the parasitic reactions during charge/discharge that lead to cell degradation.
  • During charge and discharge, lithium ions intercalate (intermingle) and de-intercalate with the the electrode material. This causes a modest, “benign” structural change of 3% in the anode and 10% in the cathode.
  • The materials used in lithium cell electrodes are stable in open air, and batteries can be assembled in open air.
    • As cells are charged, the material at both the cathode and anode become highly reactive with the electrolyte solution.
    • Fortunately, the reaction products are solid and form passivating surfaces that protect the electrodes from rapid degradation.
  • For a perfect Li-ion battery, the coulombic efficiency, the number of electrode in during charging vs the electrons out during discharge, should be exactly 1.
  • The difference between theoretical and actual coulombic efficiency, outside of the measurement area, is attributable to  undesirable parasitic reactions that lead to cell degradation.
  • With sufficient measurement precision, it is possible to predict lithium cell lifetime without intensive testing.
    • Requires at least 4 digits of precision and accuracy
  • Battery Electrolyte
    • Cyclic and linear organic carbonates
      • Ethylene Carbonate
      • Propylene Carbonate
      • Dimethyl Carbonate
      • Ethylmethyl Carbonate
    • Lithium Phosphorous Hexafluoride solute
    • Solvents are typically mixed
      • Some have low boiling points
      • Others form excellent passivating layers
  • Approximate 3-billion 18650 cells made a year
  • Parasitic reactions between electrodes and electrolytes reduce the capacity of the cell as lithium ions are consumed/trapped
    • Capacity change after first charge/discharge cycle is relatively large.
    • Loss in subsequent cycles is lower, because the reaction products form a passivating layer that protects the electrodes.
  • Extent of parasitic reactions can be quatified with a precise measure of coulombic efficiency.
    • A good cell is close to 100%.
    • 10,000 cycle life would require a cell with 99.99% efficiency
    • Need 4th digit in accuracy and precision.
  • Precision charging device
    • Developed by
      • Aaron Smith, PhD, graduated in 2012, now at Tesla in charge of Tesla’s Battery Lifetime Group
      • Chris Burns, PhD Student
    • Specs
      • 60 channels, each with precision current supplies with 5 digit precision
      • Cells under test are in temperature controlled boxes ( 0.05C)
      • Current is fed through precision resistors to measure current.
  • Longer charge cycles have higher coulombic inefficiency, and therefore more destructive parasitic reactions.
  • Coulombic Ineficiencies of common chemistries
    • Test conditions
      • Commercial 18650 cells, two per test condition
      • Charge / Discharge rates: C/24, C/50, C100
      • 30C, 40C, 50C, 60C
    • High-level
      • Coulombic inefficiency has linear relationship to charge time.
      • Strongly suggests that time under charge is the major factor in determining coulombic inefficiency for a given chemistry, at a given temperature.
    • Lithium Cobalt Oxide (LiC02)
      • Lowest parasitic reactions at 30°C
      • Moderate at 60°C, but still lower than Lithium Manganese Oxide at 30°C
      • Tesla has used chemistries with similar characteristics
    • Lithium Cobalt Manganese Oxide (Li[NiMnCo]02)
      • Moderate at 30°C
      • ~50% of Nissan Leaf and Chevy Volt packs
    • Lithium Iron Phosphate (LiFePO4)
      • Moderate parasitic reactions at 30°C, high at 60°C
      • Used by Fiskar
    • Lithium Manganese Oxide (LiMn02)
      • Highest parasitic reactions of all examples at 30°C and even worse at 60°C
      • ~50% Part of the Nissan Leaf and Chevy Volt battery pack
      • Ill-suited to use in battery packs without thermal management, like the Nissan Leaf.
  • Electrolyte additives
    • Vinylene Carbonate: reduces electrolyte oxidation on positive electrode. 2% by weight makes a huge difference
    • Trimethoxyboroxine, 1-3 propane sultone: impedence reducers.
    • Triethylphosphate and others: wetting agents to aid speed in manufacutre
    • Others for lifetime, low or high temp performance, and safety
    • Typical Li-ion cell will have 5 additives
  • Precision coulombic efficiency measurements allow impacts on cell lifetime to be assessed relatively quickly, traditional testing of discharge capacity vs cycle number requires testing to end-of-life.
    • Short term test results correlate with long term test results
  • Predicting catastrophic failures
    • Hypothesis
      • Reaction byproducts from cathode are migrating to anode, where they are reduced and gradually foul the material until the pores in the anode material are clogged. Once the pores are clogged, lithium starts plating out, and cell capacity plummets.
    • Predictions
      • The more compacted the anode material, the sooner the cells will fail.
        • This predicted behavior has been observed, and exploited to make cells that are designed to fail early in order to test other variables.
      • Coulombic Inefficiency * Cycles = A Constant
        • Coulombic Inefficiency = amount of byproducts
        • Constant is the amount of material required to clog the pores
        • A strong correlation has been observed for many additives
    • Exceptions
      • Some unknown additives from battery manufacturers have been tested and shown that make huge (20x) contributions to cycle life while falling outside the predictive model
      • Model assumes a solid reaction byproduct on negative
      • Additives may produce a reaction byproduct with different characteristics (ie liquid, gas)
    • Other observations
      • Coulombic efficiency and cycle life tend to increase with the number of additives
        • And yet most academic research on electrolyte additives only looks at one at a time.
  • New grant to put a 100 channel system on line with the capability of testing automotive scale cells
    • 10 ppm CE accuracy
  • Research Directions
    • Tests require highly uniform cells. Lab made cells can be rather inconsistent
    • Have established relationships with Chinese manufacturers of pouch cells
      • Get machine-made pouch cells without electrolyte in lots of 2,000
      • Mix and add electrolyte themselves.
      • Seal cells in vacuum sealer
    • Microcalorimeter
      • Measure the heat from parasitic reactions
      • TA Instruments TAM III
        • 12 separate calorimeters
        • 10nW sensitivity
        • Baseline stability of 500nW/month
        • Isothermal, all experiments at 40C
        • Holds AA and 200mAh cells.
      • Three sources of heat during charging (~1Wh cell capacity)
        • Entropy changes from electrodes
        • Internal resistance/polarization
        • Parasitic reactions
          • 100 uW would consume all the electrolyte in a year BAD
  • Questions from audience
    • Audience asked about the unknown additive outliers that didn’t conform to the simple model of reaction products clogging the pores on the anode.
      • Dahn replied that if those additives formed a liquid or gas reaction product, then one would expect the impedance to be lower. He then showed data showing that, indeed, the cells with outlier additives did have lower impedence.
    • Asked about using these techniques with silicon electrodes.
      • Silicon electrode cells at this point are so poor, that you can see the parasitic inefficiency with an ordinary charger.
      • Silicon electrodes need a lot of development before they need this precision.
      • Lithium Titanate
        • Incredibly durable already.
    • How can these metrics be applied to drive cycles?
      • GM wants to relate this to drive cycles.
        • Dahn’s initial approach is:
          • How does existing technology work for driving?
          • How does it look with precision charging?
          • What are the new technologies?
          • How do they perform under precision charging?
          • Based on result, he can say if the new stuff should be better or worse.
    • How do real-world discharge profiles relate to constant discharge rates seen in lab tests?
      • The biggest factor is time spent at highest voltage.
        • Longer is worse
        • Most of the parasitic reactions happen above 4v.
    • Lithium Ion Cell Overhang
      • Negative Electrode is slightly wider than the Positive
      • Prevents lithium ions from the positive electrode from plating out the edge of the negative and forming lithium metal dendrites
      • There is an overhang of graphite
      • At the beginning of charging there is some odd behavior as the ions equilibrate with the overhang
    • To extent the life of your phone or laptop battery
      • Keep it as cold as possible 🙂
      • Put it in the fridge.