Opus BT-C100 Charger Review


Yet Another review unit from GearBest! This time it’s the Opus BT-C100 Digital LCD Battery Charger. This is my first charger review; let’s just see how it goes! I will say it up front, this won’t be a lygte-info review!

Opus BT-C100 Charger Official Specs and Official Claims:

Opus BT-C100
Plug US adapter (EU Option)
Charging Cell Type LiFePO4,Ni-MH,NiCd
Compatible 10440,14500,16340,17335,17500,17670,18490,18650,22650,26650,32650,AA,AAA,C,D
Battery Qty 1
Input Voltage AC 100~240V 50/60HZ
Output Voltage 12V 1A

The above section contains the manufacturer’s descriptions and claims, not my impressions or results. Furthermore, an actual manufacturer site was not found, so those specs are from GearBest.

Opus BT-C100 Charger Review

Key Features

  • Charges many battery types and chemistries
  • Powerbank
  • MicroUSB in for charging
  • Ability to analyze cells (internal resistance, total capacity)

What’s Included

  • Charger (100-240V~ 50-60Hz 0.3A Max input, 12V 1A output)
  • Power Cable (58″ long)
  • Manual

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Here’s the full album. It’s a charger, so I didn’t get it out in the backyard and take glamour shots…. Forgive me, if that’s really your thing!


This is a cheap charger, and it feels like a cheap charger. Things work like they’re supposed to, but they aren’t too refined and sometimes they don’t quite sit right. But they do all work. I like to distinguish inexpensive and cheap. This item is an unusual category of both inexpensive and cheap. It does what it says it will do, but the parts still feel pretty cheap.

Manual and Packaging

The manual is pretty thorough, but also clearly a translated version. Some of the sections float around the manual – ie section 4 starts before 3.2 is finished, but 3.2 is on the next column and … where’d 4 go? It’s confusing, but it can be figured out.

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Might as well include the packaging here. It’s nicely printed, and very boxy. And has lightning bolts!!

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The unit can be powered by the provided wall plug (US and EU available), or by a microUSB input (cable not provided). The provided plug is (100-240V~ 50-60Hz 0.3A Max input, 12V 1A output).

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Here’s where the AC plug is inserted. Note the bending of the plastic in the bottom piece.

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If a battery is installed with 3.1V or higher, the unit will also be powered (without AC or microUSB input!). Also works with 16340 cells….

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User Interface and Operation

The manual helps here, particularly when one wants to use the Powerbank feature. Except the manual is written wrong regarding the powerbank feature. But yet again, it can be figured out.

It’s worthwhile to note up front that the mAh reading in just about any mode, isn’t what the total capacity of the cell is when it’s done charging, but what the amount of energy the charger put into the cell.

It’s also worth noting that the modes written in the manual aren’t verbatim for the modes listed on the unit. I just don’t see how how hard it is to get that right, but it is what it is. It’s clear what modes are what, but it’d be better to just have a manual be correct.

When the cell is put into the device, the mode (displayed in the inset box) flashes. One may cycle through the modes for 10 seconds, and stop on the desired mode. Mode selection can be continued if one is actively pressing the buttons to prevent the unit from going into active mode. Modes cycle in this order:

  • Charge
  • Discharge
  • Charge Test
  • Discharge Refresh
  • Impedance Test

During mode selection, one may also select at what amperage the battery should be charged at. The default is 1.0 and I found no way to change this. Cycle goes in order this way (always starting at 1.0A):

  • 1.0
  • 1.3
  • 1.6
  • 0.2
  • 0.3
  • 0.5
  • 0.7

Example pic!

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The modes work this way:

Charge: It’s a normal charging cycle, at the A you’ve selected. No special magic here.
Discharge: This cycle is meant for reducing cell memory effect. A cell is discharged to 0.9V (default, can not be changed). The mAh displayed thus, is how much was removed from the cell. The charger will nottrickle charge the cell to keep it at 0.9V. Other modes discharge at 0.7A, but this mode discharges at 0.5A.
Charge Test: Similar to refresh, but just cycles once. Cell is charged, then discharged, and charged. The displayed mAh is how much was discharged, after the cell was full. Discharge is 0.7A.
Discharge Refresh: Discharges and charges the cell three times. This is supposed to erase the cell memory effect, and restore the battery to it’s full capacity. Probably discharges at 0.7A (0.5A for the 1.5V Eneloop – discharge rate may be cell/chemistry specific) and honestly, this cycle would take quite a while, even charging at the max of 1.6A. Could be worth it, though, if your cells are quality and have bad memory. It seems that the unit determines if a cell needs refreshing. On all my cells but one, Discharge Refresh was not even an option.
Impedance Test: Very quick test (10s). The charger applies a small voltage is applied to the cell and the voltage drop is measured – this is reported as the internal resistance.

Once the cycle is going, the Mode button cycles through views on what’s going on: mAh added to the cell, time taken, internal resistance (mR), current voltage (V). I believe the IR displayed here is the same as displayed in the mode dedicated to IR (tested many cells, and they were all within a few mR) – which makes me wonder why it needs a mode for IR in the first place. Clearly measured differently (during a charge cycle, it’s not a small load applied, as with the IR test itself).

Once a cycle is going, it can’t be changed without removing the cell. This is quite annoying – I wish there was a way in the software to stop the current cycle and start a different one, even if that means the data I’m currently collecting is lost.

I tested charged cells from the unit and found that the Opus reports is very similar. I understand (but have not experienced) chargers overcharging cells – the Opus did not overcharged my cells. 18650s were at 4.2 or just under every time, measured both on the Opus and the DMM.

When plugged in but with no cell installed, the LCD reports “null”, which I found to be very annoying. I wish I could cycle and pick which mode I’d like to use for the next cell installed.

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This isn’t intended as a walkthrough video, but at least you can get some idea of how the button presses sound and feel, and how the modes cycle, etc.

As a powerbank

This charger has a useful function as a powerbank. With a cell of 3.USB (2.0) output can be used to charge USB items at 1.0, 1.5, and 2.1A. I tested this with a few USB items, and it worked great. Charging an iPhone 6 worked fine (2.1A). I didn’t measure it exactly, but being that the iphone battery is somewhere over 2000mAh, a single fully charged 18650 was approximately discharged by the time my phone was fully charged. Of course, take into account what you’re charging, and bring however many cells you’ll need to fill that battery, and you’re golden!

To use the powerbank function, hold down the Current button. Click again to turn USB out on or off as desired. Press the Mode button to confirm the setting. Charge your item via USB as desired – if the cell drops to 3.1V, USB out is disabled. While charging the lower left window on the LCD displays USB V and Ah delivered (with the accuracy of one decimal place, which truly is not that useful).

Here’s a little video of the USB output action, and here’s the USB output port. Again, note how the bottom bows….

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Build and Disassembly

Nothing much to disassemble here. There are 4 phillips screws holding the bottom inside the top casing. Removing those reveals the chargers guts.


It’s not the smallest single cell charger (that’s probably the Miller or the upcoming Nitecore F1). It’s not the only analyzing single bank charger (LiitoKala Lii-100 is too). It’s probably about the only analyzing powerbank charger that has the LCD, however. So it’s … small for those features? Hard to say.

In any case it’s about 131mm long x 41mm wide x 39mm tall. Here’s the back and you can see all those screws, and the little feet pegs that allow those vent holes to work.

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Length, and width.

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Maybe you’ll want to see what it looks like with different cells.


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16340 – truthfully, this almost requires a magnet or something to get good contact. Almost.

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18650 (unprotected)

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18650 (protected)

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Eneloop AA

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Eneloop AAA

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  • Can’t turn off the backlight
  • Initial reported V of a cell is not useful for testing the V of a cell (seems to take an initial reading which is very very general, and often very low)


Should you buy one?

Yes. Use the coupon to save a couple of dollars, but even at full price this is a great little charger. It’s a great powerbank too. It wouldn’t be a bad price just buying it as a powerbank, if you already have a bunch of 18650s. For around twice (or 3x) the amount of a Miller, you get an analyzing charger and a powerbank!


  • Completely functional
  • Powerbank feature
  • Charging amperage choices
  • Analyzes cells


  • Parts quality is low
  • Can’t change modes after mode is accepted (understandable, but annoying).
  • Cooling is [very] passive (a downside if you do a lot of discharging). (if you do a lot of discharging, you should probably see a doctor.)

Final Thoughts

Not much; I recommend buying this charger! Fine charger, great powerbank. Might not be the highest quality charger in the world, but it certainly does what is claimed.

Coupon Codes

Buy the Opus BT-C100 charger at GearBest for $11.29, with the coupon code BTC100. And remember to save 10% on regularly priced flashlights with coupon code “reddit” all the time!

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