BT-C3100 intelligent battery charger teardown


Alan Parekh of Hacked Gadgets writes:

Thanks to GearBest for sending in this Opus BT-C3100 V2.0 Intelligent Battery Charger for review. at a quick glance this charger might look like any other charger that you see at the grocery store.  Your generic store bought brand probably also has 4 charging bays for AA and AAA batteries, it probably has 2 charging circuits which places 2 cells in series to charge them, it most likely has 2 charging lights which just turns off when charging is done. If you leave the batteries in your generic charger you will most likely have batteries that have been overcharging or running down. Also your generic charger can probably just charge one chemistry of battery.

When you have a closer look at the Opus BT-C3100 V2.0 Intelligent Battery Charger you can see how this system differs from your every day generic battery charger. It can auto detect and charge NiCd, NiMH and Li-ion batteries. It charges each cell independently preventing bad cells from interfering from other cells from charging properly. Forget charging lights, this has a full LCD display that provides tons of status. It will monitor batteries that are left in the charger and keep them topped up and ready to go. From here the features go on and on. Don’t let the small package fool you, there is a ton of smarts and features built into this small package.
Have a look at the pictures below and in the video for a look inside the charger. The construction is a dual sided SMD load, the construction looks very professional. The battery contact spring tensioners work well and the connection to the PCB has been beefed up with a thick metal bar…

Via Hacked Gadgets.

Check out the video after the break.


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  1. Comes in US or EU plug versions. The mains is converted to 12V 3Amp by a wall transformer.
    Too bad for me, Australian wall plugs are different. I would need a wall adapter as well.

  2. Is it a transformer or a Switch-mode supply? If SMPS, then it’s likely wide-voltage, so just buy a cheap plug adaptor, if a transformer, you should be able to find a desktop type 12V supply for about $20 or you may even have one from an old laptop or something, Many people have loads of old power supplies lying around from old equipment.

    1. Hmmm… product page says 100-240V, very common for the brick-appliance form factor. Plug form factor usually is no big deal for anyone who has bought China-direct stuff. Plug is China type, a small adaptor may be needed. Brick looks too small to be a “traditional” brick, it’s a switch mode supply.

      Alan should do a bit more reading, the information is easy to find… ;-)

  3. We are working on a capacity tester for the common 3.7volt lithium batteries used in power banks. Sent the PCBs off yesterday. Looked into this too, cool to see Alan’s teardown today!

  4. @Ian – Will be good to see.

    @KH – Yeah, I watched the Vid and it’s an SMPS. Most of the plug-pack (wall-wart as the yanks call them) types these days have slip-on adaptors for any common world plug, but this one has the Euro type and an extra adaptor for Aus would make it sit out a long way from the wall. You’d either want to stick some foam under it to keep it from levering itself out or swap the plugpack for a local unit – would mean around $30 from a local store in Aus.

    1. For cheapest solution, I’d get an adapter plug – and a 30cm (1 ft) power lead. That moves the load from the wall to nearby floor.
      When you have large wall warts [power adapters] and twin power points, you need short extension leads – or you can’t fit anything into the second power point. As power plugs get bigger, this is becoming a common problem.

      1. At least it’s not one of those turn lever, plug pins pops out kind of thing. I have a LiFePO4 charger like that, cheap and nasty…

    2. My bad, you guys were actually discussing plugs and adaptors. Any China-to-Australia adaptors around? Of course, being in a Third World country, I would just try to solve this by using an extension unit with flexible sockets…

  5. Alan – yes that can work too, but does need a bit more room.
    KH – I’ve been fortunate with the clip-in or slide-on adaptors I’ve had to date, they have all been great, but then most were with brand-name gear. Plenty of adaptors easily available. That looks like a Euro pin to me, but China might be the same or maybe I’m wrong.

    1. Sorry, product page and review had different wall warts. The one in the product page with 2 blades is a China 2-pin (same as US 2-pin? are they all IEC Type A?). Reviewer got one with Europlug. I guess they ship different wall warts depending on location or preference or else there are different SKUs.

  6. Those sliding battery holder kludges don’t work well at all – they don’t make good contact. I have a charger (different brand) that uses the sliding contact thingys and it kept giving me intermittent BAD CELL messages. I “fixed” it by bypassing the sliding contact with a wire soldered on. But the solder joint is not long lived. I wish I could think up a better way to do it.

    1. Well, we’ve been jiggling those batteries since the days of NiCd chargers! I think chargers with fixed position contacts too are no better once the contacts tarnish. :-( No gold over nickel plating, hmmm. There are 1-cell AA or AAA holders available though, try FastTech, but that will make the charger more messy. I’ve eyed gold-plated torchlight springs, but 1-cell holders are the easier choice. Anyhow I still jiggle until they contact and try not to bump into it later… ;-)

      1. Just use a good quality contact cleaner, one that has a synthetic lube in with it. The good stuff works really well, the cheap rubbish doesn’t usually.

    1. It is even less. It only shows this charger does, uhhh, somehow charge. What a surprise for a charger.

      I learned it has a power supply, 4 independent channels, a display that shows something when you press some buttons and that the displayed data somehow meet the real data.

      I learned almost nothing about how it handles the tasks it might need its “intelligent” for. Like charging almost dead batteries, checking the capacity or training a battery. I would love to see how well it does those more special tasks.

      1. Well, there are lots of pictures, so it’s a teardown. Reverse engineering is possible, but that’s a lot more effort. Too bad he did not identify the generalities of the charging-discharging circuitry, but it’s probably nothing too out of the ordinary. I would be interested whether it’s linear or pulsed. IMHO it’s not worth digging under the epoxy to look at the microcontroller. I opened a smart NiMH charger from China, there was an SMD microcontroller, but it was some obscure Taiwan part (to us, but probably not to them). But if you probe the traces for the circuit’s operation, probably you don’t need to know about the microcontroller, it’s just a sequencer.

        Datasheets have plenty of details about charging-discharging all types of batteries, just go check a big supplier like Element14, look for charger ICs, then download and read all the datasheets.

    2. I didn’t wanted to stretch the goal that far (although I’m curious to know what is in the COB and is it possible to extract microcode and reprogram), but a little more…. Grab the voltage with and Arduino (there, I said it!) and push it into a chart.

      And for the photos there is no additional work spend into them. Identify some chips, outline some circuits, enjoy your readers/viewers!

      Perhaps sometimes “hacking” is removing some screws. Like in hacksaw.

      1. Charting is great, looking at various battery performance charts in candlepowerforums, that is. ;-) Studied plenty of battery charts there, it’s a treasure-trove of data and no need to lift a finger. But I do wish (in my case, for example) to monitor rechargeable battery performance via occasional discharge curves, specifically for LiFePO4 AA cells. Looking forward to Ian’s upcoming capacity tester project too.

        Can’t have to quality hacks all the time, heh. One nitpick though, the rechargeable battery shown in the article is a brand that often has extremely poor feedback on many sites I go to *cough*.

      2. The MCU is apparently a one-time-programmable variety, or so the lead designer said when people wanted to know if they could update their chargers to the latest firmware.

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