Dissecting third-party camera batteries, part 1: Functional misbehavior

The premise that a supposed-clone rechargeable battery is more economical than its “branded” counterpart is all well and good…unless you’re unable to actually recharge it.

As my accretion of previously-owned photography equipment continues unabated, so too grows the pile of batteries for powering them. Many of the cells are camera manufacturer-branded, but in a few situations, what’s arrived post-purchase are third-party “clones”, with the quotes referencing the hit-or-miss reality in achieving the suppliers’ desired exact-duplicate aspirations.

Recently added to my gear inventory, for example, is an OM-1 (the newer digital version, not its same-named film-based classic precursor) from Olympus (now OM System).

It showed with a third-party BLX-1 battery (7.2 V, 2280 mAh) inside it. Olympus’ BCX-1 charger unsurprisingly had no issue with the official BLX-1 cell.

Unfortunately, however, it balked at accepting the third-party mimicker.

Typically, this outcome results from a failed upfront interrogation of the battery by the charger (or camera, for that matter), done over an identification, status, or functionally equivalent bus. While cloning a simple manufacturer-and-device ID code combination stored in nonvolatile memory is rather straightforward, impersonating more complex hardware such as the entire embedded battery management system (BMS) is a more challenging endeavor.

I also wasn’t up for the common “solution” to this situation—the third-party battery supplier encouraging the user to buy its own charger—even if it were feasible. Since this battery is supplier-unbranded, I wouldn’t know where to even start looking for a copacetic charger companion. So, it went under the internal-analysis knife for my and readers’ shared educational benefit.

Electrical contact-function guesstimates

Here are some overview shots of the third-party BLX-1, as usual accompanied by a 0.75′′ (19.1 mm) diameter U.S. penny for size comparison purposes. Top:

Bottom:

Note the four sequential contacts marked “+”, “T”, “I” and “-“.

Published specifications for batteries like the one I’m looking at today are hard-to-impossible to come by, given that the camera manufacturer understandably doesn’t want to encourage cloning for economics (“branded” batteries are more expensive, therefore highly profitable to the supplier) and broader camera and brand damage-avoidance reasons. That said, the functions of “+” and “-“ are, unsurprisingly, related to the voltage and current involved in the fundamental cell-charging and -discharging functions, the latter for camera-powering purposes.

“T” typically references “temperature”, with the contact connected to an integrated negative temperature coefficient (NTC) thermistor or other sensor to monitor the internal cell(s) and alert the charger to potential overheat conditions. And “I”, perhaps short for “information” or “identification”, references the earlier-noted interrogation initially done by both charger and camera after battery insertion and power-on, and ongoing from that point on, presumably implemented by a bidirectional single-data-pin serial communications protocol of some sort.

Onward, with the comparatively bland other end, followed by the left and right sides.

Actualizing unexciting-dissection aspirations

Now to get inside. You’ve likely already noticed the tempting seam running along the entire circumference, dividing the battery roughly into two halves. Its ultrasonic welded foundation meant that simple heat application wouldn’t suffice to get them apart…not that I’d want to do that anyway, given the just-alluded-to battery chemistry overheating side effects.

I also didn’t know how (if at all, vs. elementary “pouch” structures) the cell(s) inside were encased, giving me pause when it came to contemplating alternatively cutting into the seam. And construction aside, I also didn’t want to inadvertently short out a cell via a misplaced blade. Yikes!

I eventually settled on a methodology involving my hobbyist vise and the meticulous back-and-forth use of my hacksaw blade (versus my also-considered Dremel tool’s cutting wheel…heat concerns again, though…), which thankfully worked like a charm with no “exciting” side effects.

The two serial-connected 3.7V Li-ion cells were cylindrical in form factor and unmemorable.

Note that I straightaway severed the metal straps connecting them both to PCB and to each other, in a nod to my earlier mentioned short-circuit outcome concerns.

I’d wager, however, that the mini-PCB, with contacts on one side and componentry on the other, was always of greater interest to all of you (as it certainly was to me).

Mystery ICs

Flip it over, remove the obscuring rubberized strips that normally provide the mini-PCB with both shock-absorptive and electrically insulative isolation from the cells’ terminals.

And the electronics “guts” come into full view.

The eight-lead IC U1 at far left is labeled:

8205A
Q121M1

It appears to be a dual N-channel MOSFET, a common element of elementary lithium battery protection circuits. The six-lead IC U2, seen directly to its right, is labeled:

20DBUE

Reader insights are welcomed on this one; Google was of no help! Although I can’t help but wonder, revisiting the earlier-referenced schematic, if it’s a rudimentary battery-protection IC?

Skipping past a mess of passives, the next notable chip is a 20-lead IC whose topside markings were unfortunately buffed out…that is, if they ever existed in the first place! I presume it’s the battery charge controller; make and model unknown, alas. That said, as a conceptual example, I’ll point you toward Texas Instruments’ bq2400x series, multiple of which support dual-cell assemblies (for which balancing will be necessary) and come in various 20-contact packages.

At far right is another enigma, this one six-lead and PCB-notated as U4 (or at least I think that’s what it says; the inconveniently located through-hole vias at the top don’t help). Character(s) at far left on the topside stamp represent(s), I’m guessing, an unfamiliar-to-me company logo that my limited available keyboard options won’t allow me to represent. The last four, ironically, are:

U4UH

I presume the commonality of the first two with the PCB mark is nothing more than a mere coincidence. IC identity suggestions, readers?

And with memories of recent-past short-circuited, overheating batteries are still fresh in my mind.

And knowing that the battery’s guts would be sitting in my office for several more weeks prior to publication of my teardown writeup, I concluded this portion of the project by amply wrapping both cells in insulating masking tape prior to moving on.

More to come

I’ve got two more batteries still sitting in the teardown queue, but as this initial segment went longer than initially anticipated (then again, what else is new, right?) I’ve decided to save them for part 2 in this now-series, scheduled for publication next week. Until them, I welcome your feedback in the comments on what I’ve covered so far!

—Brian Dipert is the associate editor, as well as a contributing editor, at EDN.

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