At the tail end of my September 1 teardown of EBL’s first-generation 8-bay battery charger:

I tacked on a one-paragraph confession, with an accompanying photo that as usual, included a 0.75″ (19.1 mm) diameter U.S. penny for size comparison purposes:

I’ll wrap up with a teaser photo of another, smaller, but no less finicky battery charger that I’ve also taken apart, but, due to this piece as-is ending up longer-than-expected (what else is new?), I have decided to instead save for another dedicated teardown writeup for another day:

An uncertain lineage

That day is today. And by “finicky”, as was the case with its predecessor, I was referring to its penchant for “rejecting batteries that other chargers accepted complaint-free.”

Truth be told, I can’t recall how it came into my possession in the first place, nor how long I’ve owned it (aside from a nebulous “really long time”). Whatever semblance of an owner’s manual originally came with the charger is also long gone; tedious searches of both my file cabinet and online resources were fruitless. There’s not even a company name or product code to be found anywhere on the outer device labeling, just a vague “Smart Timer Charger” moniker:

The best I’ve been able to do, thanks to Google Image Search, is come across similar-looking device matches from a company called “Vidpro Power2000” (with the second word variously alternatively referred to as “Power 2000”) listed on Amazon under multiple different product names, such as the XP-333 when bundled with four 2900 mah AA NiMH batteries:

and the XP-350 with four accompanying 1000mAh AAA batteries, again NiMH-based:

My guess is that neither “Vidpro Power2000” nor whatever retail brand name was associated with this particular charger was actually the original manufacturer. And by the way, those three plastic “bumps” toward the top of the front panel, above the battery compartment and below the “Power2000” mark, aren’t functional, only cosmetic. The only two active LEDs are the rectangular ones at the front panel’s bottom edge, seen in action in an earlier photo.

Anyhoo, after some preparatory top, bottom, and side chassis views as supplements to the already shared front and back perspectives:

A few screws loose

Let’s work our way inside, beginning (and ending?) with the visible screw head in between the two foldable AC plug prongs:

Nope, that wasn’t enough:

Wonder what, if anything, is under the back panel sticker? A-ha:

There we are:

“Nice” unsightly blob of dried glue in the upper left corner there, eh?

No more screws, clips, or other retainers left; the PCB lifts away from the remainder of the plastic chassis straightaway:

As I noted earlier, those “three bumps” are completely cosmetic, with no functional purpose:

Dual-tone and contract manufacturer-grown

And speaking of cosmetics, the two-tone two-sided PCB is an unexpected aesthetic bonus:

As you may have already noticed from the earlier glimpse of the PCB’s backside, the trace regions are sizeable, befitting their hefty AC and DC power routing purposes and akin to those seen last time (where, come to think of it, the PCB was also two-tone for the two sides). But the PCB itself is elementary, seemingly with no embedded trace layers, therein explaining the between-regions routing jumpers that through-hole feed to the other side:

We’ve also finally found a product name: the “TL2000S” from “Samyatech”. My Google search results on the product code were fruitless; let me know in the comments if you had any better luck (I’m particularly interested in finding a PDF’d user manual). My research on the company was more fruitful, but only barely so. There are (or perhaps more accurately in this case, were) two companies that use(d) the “Samyatech” abbreviation, both named “Samya Technology” in full. One is based in Taiwan, the other is in South Korea. The former, I’m guessing, is our candidate:

Samya Technology is a manufacturer of charging solutions for consumer products. The company manufactures power banks, emergency chargers, mobile phone battery chargers, USB charging products, Solar based chargers, Secondary NiMH Batteries, Multifunction chargers, etc. The company has two production bases, one in Taiwan and the other in China.

The website associated with the main company URL, www.samyatech.com, is currently timing out for me. Internet Archive Wayback Machine snapshots suggest two more information bits:

• The main URL used to redirect to samyatech.com.tw, which is also timing out, and
• More generally, although I can’t read Chinese, so don’t take what I’m saying as “gospel”, it seems the company shut down at the start of the COVID-19 lockdown and didn’t reopen.

Up top is the AC-to-DC conversion circuitry, along with other passives:

And at the bottom are the aforementioned LEDs and their attached light pipes:

Back to the PCB backside, this time freed of its previous surrounding-chassis encumbrance:

That blotch of dried glue sure is ugly (not to mention, unlike its same-color counterparts on the other side that keep various components in place, of no obvious functional value), isn’t it?

Algorithmic (over)simplicity

The IC nexus of the design was a surprise (at least to me, perhaps less so to others who are already more immersed in the details of such designs):

At left is the AZ324M, a quad low-power op amp device from (judging by the company logo mark) Advanced Analog Circuits, part of BCD Semiconductor Manufacturing Limited, and subsequently acquired by Diodes Incorporated.

And at right? When I first saw the distinctive STMicroelectronics mark on one end of the package topside, I assumed I was dealing with a low-end firmware-fueled microcontroller. But I was wrong. It’s the HCF4060, a 14-stage ripple carry binary counter/divider and oscillator. As the Build Electronics Circuits website notes, “It can be used to produce selectable time delays or to create signals of different frequencies.”

This all ties to, as I’ve been able to gather from my admittedly limited knowledge and research, how basic battery chargers like this one work in the first place (along with why they tend to be so fickle). Perhaps obviously, it’s important upfront for such a charger to be able to discern whether the batteries installed in it are actually the intended rechargeable NiMH formulation.

So, it first subjects the cells to a short-duration, relatively high current pulse (referencing the HCF4060’s time delay function), then reads back their voltages. If it discerns that a cell has a higher-than-expected resistance, it assumes that this battery’s not rechargeable or is instead based on an alternative chemistry such as alkaline or NiCd…and terminates the charge cycle.

That said, rechargeable NiMH cells’ internal resistance also tends to increase with use and incremental recharge cycles. And batteries that are in an over-discharge state, whether from sitting around unused (a particular problem with early cells that weren’t based on low self-discharge architectures) or from being excessively drained by whatever device they were installed in, tend to be intolerant of elementary recharging algorithms, too.

That said, I’ve conversely in the past sometimes been able to convince this charger to accept a cell that it initially rejected, even if the battery was already “full” (if I’ve lost premises power and the charger acts flaky when the electricity subsequently starts flowing again later, for example) by popping it into an illuminated flashlight for a few minutes to drain off some of the stored electrons.

So… Read Original