Well that was wasteful as hell. There’s a switch on the bottom of the PCB to change the top charge voltage from 4.20 to 4.35 to 3.70. You should have asked for help.
At the CRITICAL transition between charging and discharging mine would stop/reset and lose ALL information. I think that certainly has something to do with the SMPS.That is certainly a waste of time.
Sometimes four plus hours depending on what batteries were discharged.
EDIT:Several years later and with the new SMPS[and fan] that has not happened once!
It was defective as I was charging 2 18650 batteries, and it charged 1 battery over 5.04 volts and the other battery was charged only to 3.6 volts.
Same here. Tips over too easily and sends batteries flying, so I got a cellphone holder and assload of rubberbands to a) keep the batts in the belfry, and b) keep the Ope in the holder.
Similar to this… Amazon.com
Mine will discharge 4 cells @ 1amp with no problems, it’s got the standard fan that it came with but I have upgraded the power supply.
You sure it was the channel/charger itself, and not a defective battery?
I am sure the charger was the problem.
Was this repeatable? Slot dependent? What did the display say during this?
If you still have doubts that the SMPS[Power supply] does not have anything to do with discharge function, read HKJ Post #656 on the thread provided below. It makes total sense and is why me and others changed Power supplies and fans. 
I read it, I think you are confusing battery draw with power supply draw to bring that up here. Yes, he mentions power supply issues, but that was 3 YEARS ago. I’m saying I have no issues today in March 2020 with a new charger.
update
Just wanted to see if the heat issue went away so for testing I put it on top of pc fan and it’s all ok now. 
Looks like she was definitely too hot for her own good. 
Just wondering now if this overheat discharge issue is the same with members using the other chargers like Miboxer’s, Liitokala’s, Nitecore’s etc or is this just a Opus thing? I don’t have these brands but seems like they don’t have a built in fan?
I haven’t used the other brands, but I hear the Opus is one of the only ones to discharge faster than 500ma per cell. Glad you got it chugging 
Yeah first thing I chk this morning as soon as I got up. Only thing now is that pc fan is quite loud. Kinda like a gaming pc noisy. But at least the Opus is ok now, and she’s cool too! 
I understand that you are Not having issues with yours. Not all of these 3A wall warts had issues, but many did and Opus is using that same Power Supply today as they were 3 years ago.
What I am saying and HKJ is also saying is that there is a SPIKE in current during transition of charge/discharge which causes the charger to RESET. It also causes STOPPAGES which besides heat was one of the OP’S concerns.
I am not confused about battery draw and power supply draw. I am simply saying that the power supply ABSOLUTELY has something to do with the discharge function! In my original quote of yours[post #26] you state that the power supply has Nothing to do with the discharge function. That is not true!
Glad yours is working well.
Have a good afternoon
s that thread[an extensive one] will answer and solve just about every issue with the Opus BT-C3100
From what I read, Miboxer only had 1 charger model that has a discharge function (I believe it was the C2-4000?) and it had a fan, and I think discharge up to 1.5 Amps (I’m not sure if this is 1-slot or 2-slots though).
Liitokala’s (Lii-500S, Lii-500 Engr) can discharge at up to 0.5Amps (4x 0.5Amps), it doesn’t have a fan.
ZanFlare C4 can discharge at 0.5Amps (4x 0.5Amps), doesn’t have a fan.
Xtar VC8, VC4S, TC2 discharges at 0.3Amps, they don’t have fans. (Xtar VC8 & VC4S supports 4x 0.3Amps discharging, the TC2 is 2-slots)
Xtar Dragon VP4 can discharge at 0.5Amps (4x 0.5A), the model doesn’t have a fan.
I’m not aware of Nitecore with discharge testing function.
The SkyRC MC3000 can do 4x 1Amp discharging or 1x 2Amp discharging, it has a fan (previous models have 1 fan; new revision now has 2 fans).
Not very sure of the max discharge current of the single-slot Opus BT-C100, the unit doesn’t have a fan.
The Vapcell S4+ can do 2x 1A + 2x 0.5Amps discharging, if I recall correctly this model doesn’t have a fan. So this must be the highest discharging model without having a built-in fan…
I’m not very sure if the Miboxer C2-4000 (2-slot) can discharge at up to 1.5Amp, the unit has a fan — I’m not very sure if it can do discharging of 2x 1.5Amps or 1 at a time.
If it can do 2x 1.5Amp discharging, then that’s higher than the SkyRC MC3000
(since the MC3000 can do 4x 1A discharging, but to discharge at higher than 1Amp (up to 2Amps) can only be done if only 1 slot is being discharged — if I’m not mistaken, the other MC3000 slots should also not be occupied or charging if 1 slot is being selected to discharge at more than 1Amp…).
The newer sky RC mc3000 with two fans will run 7*C cooler than the one fan version .
Source, me testing one against the other ,I sold the one fan version & now have two 2fans versions.
Almost all of them produce discharge heat; charging heat also. Look at HJK’s review. He always does a heat analysis. It’s important, not trivial info.
You have to either: 1. Keep the discharge rate low to keep the heat acceptable for the electrics and battery, or 2. Get rid of the heat-easiest with a fan.
MOST of the fanless systems keep the rate slow. I STILL point a fan at almost ANY charger, including the fan upgraded Opus, if I’m charging or discharging a full complement of batteries. It’s just better for the whole package.
PC fans vary a LOT in their output and noise. Anyone that has tried to build a quiet PC is very aware of this. Lots of info on this on the web.
You can get better fans, or you can lower the voltage on noisy fans to quiet them (some), at the loss of some cooling. A 5-7v wall wart wired up to the fan will make it a lot quieter. They normally run at 12v.
I’ve also found the small USB powered personal fans you can get cheaply at drug and hardware stores are reasonably quiet and work OK.
Awesome, thanks for info peeps. Yeah those other chargers look smaller and so I was thinking “Huh no fan” but now I can think “ Huh yes fan!”
Yeah I got my pc fan rigged up to variable usb power supply which is then connected to an old 300w pc power supply I converted with 5v and 12v too. I’ll never have to worry about not enough amps now. 
Lots of go go juice now.
where can we get better fan and power supply for this charger ?
This is the thread I used for the fan replacement: OPUS BT-C3100-Stock Fan VS. Top Tier Delta fan
(typically, pictures are now missing).
You can : 1) lube the fan routinely. It’s not hard. It does not improve performance, simply keeps it from deteriorating. 2. Replace fan with same. Do a search on [Opus BT-C3100 fan replacement] and you’ll get hits on where to get some and how to replace it. 3. Replace with superior fan as above.
Note - for those not happy with fan noise of the Opus will NOT LIKE this mod. Tiny fans turning fast simply whine. No good way around it.
Note 2 - I saw a mod to 3-D print an adapter that grafted a larger fan into the space the small fan fits. This would be great if you have the tools and expertise. Increased flow, decreased noise. Or….just sit it on top an 80mm PC fan or point a small fan at it.
The power plug is fairly standard for chargers of this type. I got a cheap 12v/5A power supply from a PC recycle store. Took the charger in to make sure it fit. I’ve seen essentially identical PS sold on line for less than $10. I think the newer PS it comes with is now up to the task. Earlier PS were not if pushed at all.