Discreet Quality: Review of the sketchiest-looking 512GB Lexar SDXC card

It’s amazing how much Flash-based storage technology has advanced in the last few years, especially considering how much prices have dropped.

Naturally, when it comes to speed, capacity and price, consumers tend to look for the lowest price; as manufacturers race towards the bottom line, many will take the low road and sell counterfeit goods. This is especially prevalent in the NAND Flash market, and online marketplaces like eBay, AliExpress and even Amazon are fraught with countless fake storage devices that claim high capacities at too-good-to-be-true prices. It’s not uncommon to see unrealistic capacities sold for a few tens of dollars, but what the customer ends up receiving is a storage device with a falsified capacity that will pass a simple copy-paste test but will corrupt itself with extended use.

While browsing eBay for some deals on some Flash storage, I happened upon a very strange-looking 512GB SDXC card. It was listed as an OEM Lexar card but had no labels, selling for an unprecedentedly low price of $60 USD (the card would cost several times more at normal retail outlets). On the outside, everything about the card’s exterior seems to raise a red flag that the card is not to be trusted.

Lexar OEM 512GB Listing

eBay listing of the Lexar OEM 512GB SDXC card

Upon closer inspection, there are some hints that one shouldn’t always judge a book – er, card – by its cover. The laser-etched markings might look like cryptic gibberish to the layperson, but the markings “SM2702BAC” and “L95B” have actual meanings; the SM2702 is an SD card controller by Silicon Motion, and L95B refers to the 16nm generation of MLC NAND Flash by Micron, which owns the Lexar brand (but unfortunately is being discontinued). The seller also says that the cards have been tested, which is reassuring.

I decided to take the plunge and plunk down about $80 USD including shipping (or $105 CAD at the time) and buy a card for myself.

A Closer Look

After waiting a few weeks, the card showed up in my mailbox. The seller did a very good job packaging it, even placing the card in an ESD shielding bag before wrapping it with foam and placing it in a bubble mailer (it’s much better than the plastic wrap I’ve had some used i7 CPUs by a huge amount).


The card looks very plain, with the top label area lacking any labeling, and the same laser-etched markings on the back. The card’s contacts indicate that it has been placed in a card reader a few times before (presumably for testing).

Card Identification

I used my old Gateway M-7305u laptop with Kali Linux to see what information the card reports. These older laptops have true SDA (SD Association) compliant card slots, so they will identify as an actual SD card instead of a USB drive like with many modern laptops; in Linux these show up as devices like /dev/mmcblk0 instead of /dev/sda. By using the “dmesg -wH” command I can read the kernel logs once the card is connected to the computer.

[Jan24 10:52] mmc0: new high speed SDXC card at address 59b4
[ +0.094917] mmcblk0: mmc0:59b4       483 GiB 
[ +0.001111] mmcblk0: p1

The card reports a capacity of 483 GiB (that’s binary gigabytes, or 519.6 decimal – a.k.a. “weasel” – gigabytes), but the SD card name is ”     ” – five ASCII spaces. Everything about the card superficially rings alarm bells! However, I wasn’t phased, and decided to try the card in my Kingston FCR-HS4 USB 3.0 card reader, which uses the Realtek RTS5321 chipset.

Lexar OEM 512GB Partition

OEM Lexar 512GB SDXC card in Disk Management

Examining the card in Windows shows that the card was formatted as exFAT with a drive name of “SDXC”, suggesting it may have been formatted by the seller with the SD Formatter tool. Looking at the raw sector data in Hard Disk Sentinel suggests that the seller indeed do a full capacity test, as the data patterns match that of the program H2testw, an excellent tool for detecting fake Flash memory. This is a good sign – the seller did their due diligence and by this point I already had a good feeling that the card is genuine.

However, I wanted to test this for myself, so I ran the H2testw utility myself and let it run on the card. The write speed remained consistent throughout, which is a good indication that the card is not overwriting memory locations like in fake Flash storage (the card did get uncomfortably hot during the process, however). It took four hours to complete the write and read test, but everything came out clean – the card is genuine, even when every other sign says otherwise!

Lexar 512GB OEM H2testw

H2testw verifying that the OEM Lexar card’s 512GB capacity is genuine


With the card verified, it was time to put it to the test.


The card showed sequential read speeds of 92.03 MB/s and sequential write speeds of 60.45 MB/s; the sequential write speed coincides with the seller’s rating of 400x (400 * 150 kB/s = 60 MB/s).

The random 4K I/O performance isn’t great, especially with writes, but it isn’t bad either. The card managed 4K random read speeds of 6.644 MB/s (1700.9 IOPS) and 4K random write speeds of 0.671 MB/s (171.8 IOPS).

Lexar 512GB OEM Benchmark

Benchmark of the 512GB Lexar OEM SDXC card in CrystalDiskMark 3.0.4


In the end, I was satisfied – I got a 512GB SDXC memory card at a fraction of the cost from a normal retail outlet. It’s not exactly a speed demon, but it’s not a slowpoke either. The looks may be deterring for most folks (and rightly so), but with the right tools and knowledge, one can pick up one of these less aesthetically-pleasing memory cards and save some serious coin in the process.


Tearing down and analyzing a cheap-ass “Xtreme” $3.50 external phone battery

I was shopping around at this electronics liquidation store and stumbled upon a couple cheap buys: A “1900 mAh” external phone battery and another 4400 mAh pack (which will be the subject of another post and teardown). The batteries were originally priced at $7 and $38 respectively, but they were on sale at half price. For $3.50, I was curious enough about the 1900 mAh battery’s real capacity that I bought it anyway, expecting to be disappointed.

The pack itself is roughly half the size of a typical smartphone and about 1.5 times thicker. The casing itself has no screws; the manufacturer decided it was too expensive to use screws so they simply ultrasonic-welded the case shut. After about half an hour with a plastic spudger tool, I was able to crack the case open.

2014-01-05 00.11.26The soldering quality, surprisingly, is pretty good for a sub-$10 device, save for a bunch of hand-soldered components with flux residue left behind. The circuit board is made up of a battery protection circuit (yes, they actually put one in!), an ME2108A-50 boost converter,  something I’d assume to be a charging circuit, and an LM324 op-amp as a “gas gauge” (if you could even call it that!).

2014-01-05 00.11.36The cell appears to be a thicker version of a typical cell phone battery. It’s similar in size to something like a Nokia BL-5C which is a 1020 mAh cell, and is 5.6 mm thick. The cell in the charger is 7.7 mm thick. The charger’s cell is only 37.5% thicker but should have 190% of the capacity… yeah, no. This is not going to be very promising, given how the spot-welded nickel strips literally fell off the cell when I tried to desolder it from the PCB.

After soldering some 20-gauge solid wire to the terminals and hooking it up to a bq27425-G2A fuel gauge chip, I noticed that it reported that the fully-charged voltage is 4.25 volts. This charger tries to squeeze the most out of the cell by overcharging it! Granted, a Li-Ion cell’s maximum terminal voltage is 4.25 volts but it shouldn’t settle down to this voltage after charging!

1900 mah charger overvoltageAfter performing a few learning cycles to determine capacity and resistance, the cell holds merely 1370 mAh. The internal resistance is about 85 milliohms, which tells me that at least they used a relatively fresh cell in this charger and not just some recycled cell (*cough* UltraFire *cough*).

1900 mah charger graphI knew from the get-go that this battery was going to be a let-down, and I was right. But hey, for $3.50 I get a half-decent 1370 mAh cell and a few scrap chips (no way I’m reusing that battery’s PCB as-is!). But my verdict: Avoid this battery pack if you intend to use it to, I dunno, charge your phone. 😛

Skin-Deep Authenticity: Tearing down a “genuine fake” Samsung Galaxy S II battery

When you have the same smartphone for almost 3 years, it’s likely that your original battery’s not going to last as long as the service contract. And as long as you’re not an iPhone user you will probably look into a replacement or spare battery.

coverMy first replacement cell was a 2-pack of “1800 mAh” batteries for $5. These had 66% of the stated capacity and TI’s Impedance Track gauge said that the DC internal resistance was about 250 milliOhms. That’s… pretty terrible. Those two cells quickly led their end in a battery recycling bin. My next two were “genuine” cells from eBay. They cost about $12 each and had rather authentic-looking labels on them too. Their performance was pretty good, but one of them became all bloated so I decided I’d take a look at the cell that’s inside. I peeled off the label, and the truth comes out…

2014-01-01 04.53.39This battery was an outright lie in terms of capacity! 1350 mAh is about 80% of the 1650 mAh capacity that was written on the outer label. The cell’s manufacturer is unknown, but the battery markings read “BMW-524655AR 1350mAh 2012.09.03.1110”. Wait, look at that manufacturer date. Something’s fishy…

2014-01-01 04.53.54The outer label states a manufacture date of July 20, 2012. The internal cell states one of September 3, 2012. Unless this battery was manufactured in a time-bending factory, then these batteries certainly aren’t genuine.

Next up was the protection circuit. The “genuine fake” battery uses a DW01 protection IC and uses a generic 8205A dual NFET for swiching. And there wasn’t even a thermistor; the PCB uses a 1.5k ohm resistor to simulate one. A genuine board uses a single SMD package that integrates the FETs and the protection IC.

Below is a comparison of the protection board of a fake battery and a “genuine fake” one. At least the “genuine fake” uses the same black appearance of the original.

The “genuine fake” battery, after only 2 months of usage (not even 20 charge cycles’ worth), became so swollen that I can’t keep the back cover on. Running this battery through a bq27425-G2A battery gas gauge determined that the real capacity of the battery is a paltry 944 mAh, with an average internal resistance of 187 milliOhms. Absolutely pathetic.

samsung galaxy s ii replacement battery old ra graphGoes to show you get what you pay for. But some things may be more deceiving than others…