So, about that Kentli battery…

It’s been a while since I’ve posted about the Kentli PH5 battery, which is a Li-ion cell with an integrated 1.5-volt regulator, wrapped up in an AA-sized package. Although I haven’t written much about its performance yet, that doesn’t mean I haven’t been doing work on it. In fact, I’m sure I have never put so much work into a single blog post before!

The full analysis of the battery’s performance is not fully complete, but I’ll reveal some details of my test setup and what I’m currently working on:


I’m doing a much more thorough analysis of this battery than I have done with any other one on this blog. I have created a second bq27541 fuel gauge board, but with the explicit goal of measuring the voltage, current, passed charge (mAh) and temperature of a given DC-DC converter. This way, I can measure the input and output of the DC-DC converter simultaneously, greatly enhancing the data I can collect.

These are the data points/attributes I am currently collecting:

  • Battery voltage sag at high load currents
  • Battery capacity over different load currents (it’s not constant!)
  • DC-DC efficiency, both at different load currents but also over a single discharge cycle
  • Temperature rise of the DC-DC converter at different loads, and also over a single discharge cycle
  • Changes in battery capacity and internal resistance over many charge cycles

I want to be as thorough as possible with my measurements, mostly because nobody else has done a detailed performance review of this rather unusual battery, but also partially because I want to challenge myself and see how much of a “real engineer” I can be (#JustHobbyistThings). :P

Teardown/review of Silicon Power 8GB 200x CompactFlash memory card

Hooray for nice hand-me-down SLR cameras! I finally have a better camera than the one built into my (now ancient) Samsung Galaxy S II that I use for pictures on this blog. The camera, a Canon EOS 50D, had an 8GB CompactFlash card that I was preparing to erase and reuse, and had problems trying to read out the card’s contents; a few stubborn files would refuse to copy and Explorer would simply hang until I restarted the program or unplugged the card. Additionally, when using my Hard Disk Sentinel program to do a surface scan, it too would freeze when reading a certain sector on the card.

Instead of using a USB-to-CompactFlash adapter (I could not find my card reader and have not seen it for over a year now, come to think of it) I used a CompactFlash-to-PATA adapter, then a PATA-to-SATA adapter so I could directly hook up the card to my computer. In addition to having greater theoretical throughput, it allows me to view the S.M.A.R.T. diagnostic data that the card provides.

Memory card issues and performance

The diagnostic information doesn’t really provide any insight into the health of the card; none of the S.M.A.R.T. attributes are listed as critical, and many of them are listed as vendor-specific. Oh well, at least it gave me some sort of information…

After finding a copy of the card’s contents on my home server (I seem to have previously backed up the card before the corruption occurred but didn’t recall doing so until I had raked through some of my archives), I decided I’d do a full card erase and see if it would cause the card to be usable again. I called up the Surface Test in Hard Disk Sentinel and used its surface-write tool to erase the user-accessible area of the card. A few blocks seemed to write dramatically slower than the rest and repeated write tests did not resolve their sluggishness; I call shenanigans with the memory card’s controller and its reluctance in reallocating problematic sectors…

The card itself isn’t very fast. The sequential I/O of the card is good enough for casual photography, but I would definitely not use this card in an embedded system that uses a CompactFlash as a sort of mini-SSD; even though it shows up in my system as a hard drive (non-removable), its random I/O is quite sluggish and its random write speed is worse than that of a standard hard disk drive.


The card itself is a sandwich of aluminum plates, a plastic case and the PCB assembly that holds the controller, Flash memory and the CompactFlash connector. A hobby knife run under the aluminum plate was able to separate the plate from the plastic body; some glue and a couple clips were the only things holding the card together.

The card’s controller is a Phison PS3006, which sports a PCMCIA (and therefore CompactFlash) interface with True IDE (or plain PATA) support. It contains an 8051 microcontroller core with a few components to assist with interfacing with the Flash memory, such as a hardware ECC (error correction code) engine and a small amount of SRAM for a buffer.

The datasheet for the PS3006 doesn’t provide information on the S.M.A.R.T. attributes, nor does it indicate what type of Flash wear-leveling is provided. Given the controller’s limited computing capabilities, I’m thinking it uses a less-complex but less-reliable form of wear leveling, known as dynamic wear leveling (see Micron’s application note for more information). It’s less capable of dealing with memory wearout, but doesn’t require the computing overhead of static wear leveling (which proper SSD controllers use to keep performance up).

The memory is an Intel 29F32G08AAMD2 device, which is an asynchronous MLC NAND Flash memory chip. There are two installed on this card with another two footprints on the PCB being unpopulated, suggesting that the 16GB version of this card has all four footprints populated.


Given the simplicity of the card, I don’t really have much else to add about this card. Either way, it’s lost my trust with regards to holding my photos. I bought a NOS Disk 16GB CF card from Amazon as well as a SanDisk Extreme 32GB, and plan to use the latter to hold my photos, with the former mainly being a simple curiosity of the construction of a card from a lesser-known manufacturer. Hopefully those will also provide S.M.A.R.T. data, as I prefer Flash-based storage devices with some sort of S.M.A.R.T. data capability. (Is it an insatiable thirst for knowledge? A means of doing regular ‘check-ups’ on my storage device? Probably the latter, but maaayyyybe the former as well. :) )

Ramble: I really need to get more content on here…

Wow, it’s almost February and yet it only feels like the new year has just begun! That also means that I haven’t put out any new blog posts recently, and I need to change that.

Upcoming blog posts include:

  • Teardown of genuine, and “semi-fake” iPhone 6 and 6 Plus batteries
  • Creating a USB charger/power bank analysis tool with a bq27541 fuel gauge chip
  • Attempting (and failing) to directly connect the SanDisk Extreme USB 3.0 drive’s internal SSD to the SATA bus on my computer
  • Teardown and analysis of some Costco-purchased power banks

Ramble/WordPress auto-post time: 2014 in review

The stats helper monkeys prepared a 2014 annual report for this blog.

Here’s an excerpt:

Madison Square Garden can seat 20,000 people for a concert. This blog was viewed about 66,000 times in 2014. If it were a concert at Madison Square Garden, it would take about 3 sold-out performances for that many people to see it.

Click here to see the complete report.

Teardown of Kentli PH5 1.5 V Li-Ion AA battery

After having an entire month of dormancy on this blog, I’m finally beginning to cross off the blog posts on my “Pending” list.

Last year, I made a blog post talking about Kentli’s lithium-ion based AA battery that has an internal 1.5 volt regulator. The first order never arrived, and the second one had arrived a few months ago but I never got to actually taking one of the cells apart. That changes today.

Cell overview

The battery itself looks like a regular AA battery, except for the top positive terminal. There’s the familiar ‘nub’ that constitutes the 1.5 volt output, but also has a recessed ring around it that provides a direct connection to the Li-ion cell’s positive connection for charging.


After peeling the label, we are met with a plain steel case, save for the end cap that appears to be laser spot-welded. Wanting to take apart the cell with minimal risk of shorting something out inside, I used a small pipe cutter to gently break apart the welded seam. Two revolutions and a satisfying pop sound later, the battery’s guts are revealed.

Battery internals

The PCB that holds the 1.5 volt regulator is inside the end cap, with the rest made up of the Li-ion cell itself. Curiously enough, the cell inside is labeled “PE13430 14F16 2.66wh” which is interesting in more than one way. First of all, the rated energy content of the cell is less than what’s on the outside label (2.66 watt-hours versus 2.8), and the cell inside is actually a Li-ion polymer (sometimes called a “Li-Po” cell) type; I was expecting a standard cylindrical cell inside. Unfortunately, my Google-fu was unable to pull up any data on the cell. I might attempt to do a chemistry identification cycle on the cell and see if TI’s battery database can bring something up.

Battery circuitry

The end cap’s PCB uses a Xysemi XM5232 2.5 A, 1.5 MHz synchronous buck converter to provide the 1.5 volt output. According to the datasheet, it is a fully integrated converter with all the power semiconductor components residing on the chip itself. The converter is rated for 2.5-5.5 volt operation, well within the range of a Li-ion cell. Additionally, it has a rated Iq (quiescent/no-load current) of only 20 microamps. The buck converter’s 2.2 microhenry inductor is magnetically unshielded which may cause some increased EMI (electromagnetic interference) emissions, but I don’t have the equipment to test this.

I was looking around for the battery’s protection circuit, and found it on the flex PCB that surrounds the Li-ion cell. It uses a Xysemi XB3633A protection circuit which, like the buck converter, is a fully-integrated device; there are no external protection MOSFETs for disconnecting the cell from the rest of the circuit.

More to come…

I have not yet done any performance tests on this battery; those results will be posted as a separate blog post, and hopefully I’ll have the drive to make graphs of battery performance at different loads and such. Additionally, I’ll have a teardown of the charger that’s designed specifically to charge these batteries. Stay tuned!

(Day 3 and 4 of 4) Mini-Ramble: Dallas! TI! Batteries!

Oh wow, already a week since the event finished; I need to get posts written up more often!

Anyway, the last 2 days of the event were pretty much information seminars with three separate ‘tracks’ with one of them being all about fuel gauges (you can guess which one I went to :) ). They discussed the reasons that fuel gauging is so important (and why “just measure the voltage” usually isn’t good enough), and also explained why your battery life just plummets after a few hundred cycles or 20% wear.

One of the main fuel gauge guys at TI gave me an evaluation board for their latest-and-greatest fuel gauge, the bq40z50. This gauge is able to handle 1-4 cells in series, which means that you can now pack a laptop battery’s smarts into a battery meant for a smartphone or tablet.

I’d post more but these few posts were “Mini-Rambles” after all. I may post a few pictures later on.

(Day 2 of 4) Mini-Ramble: Dallas! TI! Batteries!

Today was the first day of the actual Texas Instruments Battery Management Systems event. To my surprise, a couple hundred of people showed up from TI employees, a lot of customers (representatives from various companies like Bose, Google, and many others), and me as well. :)

The first day was a basic but still detailed introduction to the inner workings of Li-Ion technology as well as its limitations, failure modes (the gas coming from a Li-Po [lithium-ion polymer] cell contains carbon monoxide, hydrogen and a bunch of other gases), with this leading towards battery fuel gauges and why just measuring the voltage is not enough to accurately determine how full a battery is.

The day ended with a lab showcasing TI’s new Gauge Development Kit (GDK), which, in layman’s terms, is a “battery lab on a board”. It includes PC communication hardware, an adjustable charger, adjustable load and an on-board fuel gauge (but it’s set to use an external fuel gauge by default). I even got a chance to talk the TI battery management team, and even had a dinner with a few key TI guys including the one who made THE design for the GDK.