With some pc fans the Opus can sit right on top of it so no mounting is required. I have everything including the fan powered from a desktop power supply so the fan comes on whenever the chargers are running.
This shows the Opus off the fan:
This shows the Opus on it:
Brand new 3400 18650 cells from Mtn Electronics discharge test on the Opus V2.1…
3346mah on bay 1 and another at 3396mah on bay 4 discharging at 1 amp. Both had their 1st charge on the XTAR WP2.
I’d say the Opus is pretty close to what it should be but I definitely suspect that bay 1 and bay 4 are getting slightly different readings.
I don’t think it is totally coincidence that bay 4 is always reading higher on what are otherwise pretty well matched cells.
Happy to see this level of performance in these 2 cells.
Hi 
I just wanted to post an update - thanks to help from Muto and a person from different forums, I was able to replace the 25x25x07 fan with the Sunon one (25x25x10). I’ve used an utility knife (due to the lack of better tools) to trim down plastic fins/shelves that hold the fan in place and to cut out a bit of the main board, just enough for the new fan to fit in tightly. The new fan is certainly an improvement over the old, rattling one, though I wouldn’t call it silent. I’m going to buy a laptop stand to see if that stops the small fan from starting up.
I think that the engineers of Opus should consider replacing the current fan (10000RPM, 1.1CFM, 25dB), with a 25x25x10 one. This only requires a few millimeters of adjustments in the design and similar airflow could be easily achieved with 5000-6000RPM and around 16dB.
The future chargers should definitely use a cooling solution more like tatasal’s or SIGShooter’s. BTW. Do you think that a pulling or pushing fan is better?
Best regards,
Crocodil
Come on admit it. For all the faults that you have uncovered in this charger, you’re loving it!
Wouldn’t it be boring if it was just the PERFECT charger and you couldn’t improve (personalize) it?
Isn’t that what this forum is all about anyway? 
haha, you bet… +1 !
This Opus is the most expensive charger I own. Personalizing shouldn’t be necessary.
I like to know that my cells are being charged properly. This unit won’t see the duty cycle my XTAR is providing.
It may serve my NiMh stock and to confirm capacity of new cells and aging cells. That’s about it.
I’m still waiting to hear back about what GearBest will do about my suffering fan.
Did anyone else notice the BT-C3100 (v2.1 and v2.0) is now on sale for the next 3 day for less than the Group Buy price?
http://www.gearbest.com/chargers-batteries/pp_71596.html
$39.65 without the GB code. If you use the GB code it goes up to $39.99.
Really hoping this would go closer to $25 or $30.
Well, I still haven’t heard back on my fan issue.
Does anyone know how to use the refresh function? I understand that this is for NiMh cells but should it finish at some point or will it continue to charge/discharge until you terminate it?
i bought another one for a friend with that price 
The answer is: charge refresh shuts itself off when the cells show FULL. Took all day to get 4 AA NiMh up to snuff. Not sure what the capacity ended up being.
I just picked up this charger up to fix all these problems Then I’ll wave it around like it’s the best thing since pita pockets
Actually on a serious note… I found it’s not hard to adjust the end termination voltage on any charger if the end voltage is too high. You put a cap from the positive end with a resistor on the negative in the bay you want to adjust. This could be hardwired in I guess if you had it apply only when a battery was in charge- else the charger sees the cap as a battery
I used all types of resistors from high to low at the start until I was in the ballpark. Too low and the charger will think the battery is full at any voltage. Then I added a variable resistor to fine tune the end voltage per bay. I guess you could then get the right resistor for the job and you have a perfect 4.2v charge every time.
That would work if it was a CC charger at the end of the cycle, but its not. It is a very noisy signal that only my analog meter can give some reasonable indication of what’s truly going on. Problem with these is that the noise is well over 4.2V. I don’t want any of my Li-Ion cells seeing anything over 4.2V. A long time ago I used cheap <$5 chargers, and every one of those had an open voltage of well over 4.2V and termination somewhere between 4.1V and 4.25V. These use interpolation to determine the end of the charge, typically a current reading. But if the signal is noisy, the termination too is less than accurate.
I noticed that my Opus 2.1 won’t charge NiMH batteries that have a resting voltage around .9volts are less. They would sit there for 15 minutes or so and then the display would flash FULL. FWIW I was charging at 700mA.
After charging them for several minutes on a hobby charger they seem to be charging ok on the Opus. Anyone else notice this about the Opus?
SUNON MC25101V1-000U-A99. (25x25x10) (See my post in Russian.)
6 months to successfully use this replacement fan. I plan to buy a fan on future F251R-12L3B (9 dB and 5500 RPM)
Thank you KAR2009 for a great visual tutorial. I’ve already managed to put my SUNON fan (supposedly a bit more quiet) inside the case by removing a bit of plastic and of the mainboard.
I’m affraid that no 25x25mm fan is ever going to be trully quiet so when my patience runs out, I’m planning to attach a bigger one (preferably 80x80mm, slow RPM) on the bottom (something like tatasal has done).
I still haven’t heard anything back from Gearbest! :weary:
Having to do this for a $42 charger is not acceptable!
Here is what I did to make the fan tolerable for the time being.
@NightSpy , I’m sorry to make you wait the answers so long, and now we have the answers about the fan problem from Henry
” the problem about the fan is almost solved, we now have new fan, its new lubricating oil can work with high temperature so that the fan can be more quiet than the old one ( the old fan’s lubricating oil can’t work with the high temperature very well, so after using for some time, it has been dry, then making noise), in our future production, we will use the new fan, and if customers think it’s necessary, we can provide the new fan”
So NightSpy and other members if you think it’s necessary to get the new fan, please PM me with your order number. or buy it directly here http://www.gearbest.com/diy-parts-and-tools/pp_122241.html
Good Day CSgearbest, 
That is Great news.
When will the new replacement fans ship to us?
Thank You Very Much,
Best Regards,
George
PS:
You have PM.
PM sent with order number.
Any news about the improved fans? When will they be available/shipped?