I have an opus BT-C3100 too. If I want to charge a 0.00v battery, like a NiMh, I set my power supply to 1.5v and 0.25ma. I hold it against the battery for 20 seconds or so, then pop it in the charger. Works every time. Of course if it’s this dead because of self-discharge you should just trash it anyway.
Thanks everyone. The fan sounds pretty smooth, but I’ve got some silicone lubricant spray anyway - I’ll pop a little squirt in through the grill if I can.
Is the Opus’ discharge/refresh cycle worth doing on older batteries? Does it actually refresh them to any useful degree?
Edit: I asked about mA again, but just realised that someone has already answered mA for charging. I’ll try 200mA for AAA and 500mA for AA and see how that goes.
The temp of NiMh is supposed to rise during charge, so stick with that. As for refresh, heck yes, it’s absolutely worth it.
Please don’t “pop a little squirt in through the grill if I can.”
You have to get to the bearing, only way to do that is to take the charger apart.
If it sounds smooth but is loud, that is normal, leave it alone at this time.
The refresh cycle takes forever, I never use it for that reason, the Nimh are too cheap to worry about saving.
HTH
Don’t worry - I wasn’t going to just blindly spray through the grill! I was hoping I could get to the bearings using the little spray tube without taking it apart - I hadn’t had a chance to inspect the unit to see what the access was like. If I couldn’t, I wasn’t going to bother taking it apart as it sounds OK to me. Given you suggest the same, I’ll leave it for now.
I’m happy to try a refresh - I’ve got the time, and if I can get a few more reuses out of them before recycling I might as well.
Thanks for the help everyone. I’ll stick with the Opus and see how I get on.
Welcome to BLF ” Dazed and Confused ” 
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I would not leave it unattended while charging. Does it emit any electrical smells ?
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I had to bend the movable negative contacts towards the positive contacts to get any contact on big batteries like a 26650.
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Here is a good tear-down thread to look at. Review: Opus BT-C3100 V2.1 (with teardown and video)
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If you keep hearing strange noises when the fan is off, you probably should not use it until determining what that is. 
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Please come back here and keep asking, guys with a lot of experience are in and out here so try to give them time to notice this thread.
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You did not make a bad choice, the Opus BT-C3100 v2.2 is a good charger, I use mine a lot with no problems.
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I had some AA NiMh that tested between 0 and 5 mAh each. I ran a full refresh cycle on each battery twice. Then they tested at 500 to 600 mAh. Thats like new for some brands. Totally worth the time.
To lube, the fan needs to be taken out, a sticker on the back removed, THEN you can access the bearing. FWIW pretty much all computer fans are similar and can be lubed that way.
Clean up the area well to get the lube off, cut a new disk of duct tape or similar and seal it again. Put a sticker (I use easily removed painters tape) on the outside and date it.
I used the same tape sticker process to track my batteries, until I got one of those labelers. It’s a good idea to be able to track their status over time.
I also have an Opus BT-C3100 charger (version 2.0). I’ve had it for years and never had an issue with the charger or the fan. The fan has been quiet since I first got it and I’ve never lubed it.
I also hear a slight fast ticking sound that you are concerned about Dazed and Confused. I believe that is from the pulse charging and shouldn’t be a concern. But maybe you’re hearing something different? Either way, just monitor it for awhile until you feel comfortable that it is working properly.
Be very careful with silicone spray lubes. Some of them use solvent carriers that act as plastic glue, similar to the type of solvent glues used in plastic model assembly. I inadvertently ruined a plastic calculating device that used rotating rings marked in increments by not reading the directions on the spray can and ended up gluing the rings solid.
I've had a Opus 3100 2.2 for a few years. It's always worked well. I stand it on end when in use, fan end up, to let natural convection aid with heat removal.
slmjim
Be aware that the thermal protection may fail so don't leave it unattended :(
https://budgetlightforum.com/t/-/61627
The BT-C3100 has temperature sensors, but the software ignores them during the charge cycle. At least that’s what I observed.
Thanks everyone. I’ll leave the fan alone for now, and it sounds like other people have heard the very faint fast ticking, which is reassuring. I think I’m good to go! I’ve chucked a bunch of AAAs on refresh, and I’ll see what happens.
I do plan to use it in a car overnight when camping too, and picked the Opus because it supposedly had protection from overheating. It seems from the comment above like it is designed to do that, but in practice maybe not?
I’ve never seen it shut off while charging an 18650 because of heat. And I allowed one to go as high as 190F (88C) just to confirm. So yea. Apparently there is a software bug.
I’ve charged at 1000 milliamps in all 4 slots many, many times and never had an issue with heat. The fan does a good job keeping the temps down.
I have no doubt NeutralFan, but that’s because your batteries are good. If you pop in a battery with very high IR, no fan can stop the thermal runaway. Apparently they didn’t test that software feature, and it has a bug.
Hmm, how does it (or should it) sense the cell’s temperature? Conduction through the springy-thing?
I assumed “thermal protection” was just for the innards, not the cell itself.
You can see the cell temp sensors at the top of this pic.
The doodads wired to “TH1” through “TH4”?
Huh… interesting.
THermistors, yea.
Some poor guys have been hooking all those up, and they aren’t even fully functional.