$37.99 for Opus BT-C3100 V2.1 with OP3100 ( clearance) & $38.99 for Opus2.2 without using the coupon @GearBest

Overwhelming % of units sold aren't even tested for this I'm sure, so, owners aren't aware. It's dangerous to assume only the 2-4 units reported here are the only ones, or represent the below 1% of total units sold. If they carelessly sell units that are 0.07v reading high, are they selling units that are 0.07v low? What about 0.09v low? What if all your cells are charged to 4.28v instead of 4.20v? Will a typical buyer even be aware of that?

Where I work, we'll have a firmware/software bug, fairly significant that breaks a functionality and it's out there for years in 100's of units sold, unreported, at least to us. Why? Lots of reasons - users find a work-around or simply stop using the feature and don't want to be bothered reporting it, or they simply never used the feature, or use it in a way to cause the bug. Maybe it takes over 1,000 sold units to get the single one report in of the bug after 2-3 years, but 100% of the units sold had the bug.

Since Henry Xu had been very active here, and appeared to make sincere efforts to address our concerns then, I'm hoping by raising this issue, that it gets investigated at least. I asked GearBest in my CS reply if they could report it to their supplier. I should check the box/manual, etc. for any contact info for Opus - not sure if they list anything... I don't know how to get online to the manufacturer.

Well, it looks that since your charger is perhaps one of the very few reported to be defective, while I look at it as the minority, you look at your case as perhaps the majority, with most of the ‘typical buyers’, as you term it, not aware that their unit is having the same problem as yours,….

Oh well, it now looks that it depends at which vantage point people look from.

Smile - please don't make implications and assumptions about what I feel behind my words - facts are facts.

One problem with Chinese manufacturing…
A factory can make 10,000 perfect units and the next day make 10,000 defective units.
The problem is, both units will remain in the supply chain for years.

Once a serious defect is discovered in one batch, it is best to just stay away from the model all together.
This is a similar issue when a clone item hits the market that is not distinguishable from the original; best to just avoid the brand.

Tom… no offer for a full refund? PayPal may have something to say about this now that you have a letter from the manufacturer acknowledging a problem.

I discharged a 18650 laptop pull after charging it in slot 1 of my Opus. It was at 4.16v on my DMM but I don’t what it came off at an hour of so prior to looking at it. Below are the numbers for when it was fully charged to 4.20 on my hobby charged and then charged to 4.16 on the Opus

4.20v - 2016 mAh (unknown slot)
4.16v - 1980 mAh (slot 1)

For this cell the 1.8% difference would likely not be noticeable in real life usage for me.

Thanks… that is probably within the margin of error between discharge runs or devices.

The main purpose for going for the Opus is to determine cell health for the cells I use every day. Also to weed out imposters when buying new cells. I trust that the Opus will be accurate enough for that. Also some NiMh compatibility will be welcome.

I just checked 7 assorted LiIon cells between the Opus BT-3100 v2.0, v2.1, Fluke DMM, and UNI-T UT33D DMM (sells for $15 but a good one...). For all 7, the two DMM's read the same exact values to the 1/100th volt. The v2.1 was 0.06v high on all 7 and the v2.0 was 0.03v to 0.04v low. The cells were 2 14500's, 3 18650's and 2 26650's. All cells were in the 4.01v and 4.23v range.

I checked the unit, the box and op instructions of the Opus and there is nothing on the manufacturer - only one place "Opus" is mentioned on the box, one place on the unit. No contact info at all... Typical I suppose but it sure is not like an Xtar, JetBeam, or NiteCore.

Another set of tests:

SONY, pack pull SF US18650GR: 3.05v on DMM's, 3.09v on Opus 2.1, 3.01v on Opus 2.0

Samsung INR 18650 15M: 3.23 on DMM's, 3.27v on Opus 2.1, 3.18v on Opus 2.0

The Opus 2.1 gets closer to the DMM readings for cells at lower voltage levels, while the 2.0 gets further away... In fact the Opus 2.1 is maybe a tad more accurate than the Opus 2.0 at lower voltages.

Again, I don't mean to imply you will see these results typically - mine could be the 1 of 1000 units sold, but it also could be the 1 of 10 units, one bad apple (at least one other reported though), or a bad batch - no telling at this point. Just wish there was a way to reach Henry Xu...

4.15V "FULL" for my v2.1 unit . Tested with 5 different batteries from 14500~26650. I thought v2.1 is suppose to be quieter with new fan? Or v2 is even worst than it? I do not think I can charge battery in my bedroom in future ...

@Tom E your not alone, 4.14 at the highest reading FULL on my new Opus V2.1 DMM Fluke 116 and X TAR VP2 confirms this? Just opened it and charged KK’s Kinoko’s, Keep Power’s Samsung’s and Panny’s every one of them 4.14 - 4.11 avg between the 4 slots? It’s accurate but low? And what really suck’s no indication light when it’s “on” ?

I'm not alone.... Cry We should keep count somehow... Ohh - I tried some cells at 4.35v and it stops at what it says is 4.35 but is actually 4.28. So, the error is more like a % factor as opposed to an offset - the higher the voltage, the more the offset is. Henry stated +/- 0.03v at 4.2v, but:

  • Operating Instructions in 11. Technical Data for 2.1 Voltage Deviation says: <0.03v @4.2v

  • Operating Instructions in 11. Technical Data for 2.0 Voltage Deviation says: <0.04v

Not sure if anyone posted about the 4.35v setting in their reviews (couldn't find it in Chloe's and HKJ didn't test it), but important to note that if you put a LiIon cell in the charger that's at 4.24v for example, it says FULL but will still allows you to start the charge cycle and run it based on the 4.35v max (or what it thinks is 4.35). I cut out a hole in the case on the bottom over the switch so I can flip the switch with a pick tool without having to remove the cover.

We received your support ticket on Gearbest.com. Thank you for the opportunity to provide the best support and advice to you.

This is your ticket ID: T33068448793. Our Customer Support Team is busy processing your ticket and will reply to you very shortly. This generally occurs within 24 hours, except weekends and public holidays.

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Thank you again. We always appreciate your patience and cooperation.

Well, the whole problem is in the choice of resistor precision. I am sure Opus saved a huge $0.10 on a 5% rather than a 2% device… or they opted for a substitute because the required device was not available and the factory needed to keep churning for the next 100,000 units. So we have a run of 100,000 Opus V2.1 charges that will not meet spec.

If Mr. Xu wishes to save face, I would suggest that he help identify these resistors and their proper calibration. This will likely affect 8 circuits in the charger so this is a little more than a quick fix. Point of order, someone screwed up!

I’m just getting into this, and I figured I get this and learn to use all the features/functions as I went along, I guess I took for granted that even my $8.00 no name charger, my I4 and my XtarVP2 have an indicator “ON” light and hey “your done charging” light? State of the art huh? Now you have to HAWK over your charger for the end result, it doesn’t fully charge my batteries, just great! J)

Gearbest Customer Support At :10/18/2014 12:52:51 AM

Thank you very much for your recent order with Gearbest.

We are so sorry for such a situation, if the item really can’t work well, how about you return them back, we will give you full refund, is that OK?

Waiting for your message.

Best regards,
Gearbest Customer Support At :10/18/2014 01:58:19 AM
My reply - O.K. are you paying for the return shipping? If so I will return for a full refund PLUS shipping back to you.

One of my Panasonic indicated Full on slot 2 when it measured at 4.12v??? Wtf. i switched it to slot 1 and restart the charger. Displayed value showing 4.18v this time. Cannot believe ppl actually paid $65 for that.

Thanks for the replies, you guys saved me $42! :open_mouth:

Will sit back and see how GB solves this issue, maybe the next batch will be better… :~

My cells are reading at 4.20 on the Opus 2.1 and testing at 4.18 with my DMM, not enough of a discrepancy for me to lose any sleep. Ideal really IMO.

Buy the 2.0 and then upgrade the power supply if you plan on charging 4 cells hard.
Most of them seem to be within .02-.03.
My Opus 2.0 charges to 4.22 consistently unless I have a bum cell then it will stop at 4.18, same cell stops at 4.18 on Nitecore i4.

Here’s what I am not getting, pretty much all of HKJ better brand battery discharge tests show that all batteries drop off of 4.20 like immediately and go way below 4.15 as well, like off a cliff.
So, what is the big deal of stopping a few hundreds of a volt short?
Is it not better for the battery vs over charging?

Personally I will label a charger if it stops at 4.18 as a keeper vs one that goes to 4.25 or is random.
JMHO, your hundreds of a volt may vary:)

Been meaning to post this;

This fan will go right in the case just buy grinding down the 2 shelves at the bottom of the fan mount. They don’t need to be removed completely but close.
You will need to undo the springs on the battery slides and wiggle the LCD loose from the top of the case to get room to work.
While you have the case open, dremel out an opening for the voltage switch and label the outside of the bottom with a P-Touch.
The fan connector is the same, it is plug and play.
Still noisy, but it does not need oiling and runs when needed. Also seems to move more air than the orig. one.
Best $1.95 I have spent this year.

+1 - under 0.03v as is spec'd for the v2.1 would be fine with me too - if only mine was within that spec... My Opus v2.0 is good with the 0.03v offset (reads low).

I am happy with GearBest's support on this issue, though I wish they would acknowledge a problem and get report it back to the manufacturer, or at least address it here on their own sales/GB thread.