It’s about the same noise level as anything else with a medium-speed fan that size. (25mm? It’s a very small fan.) Definitely loud by general consumer product standards, but not loud by mid-to-large power battery charger standards.
It’s probably about the same volume level as my hobby charger, ignoring the noises the Opus makes when the fan first starts (the not-enough-oil-in-here noises). Once it gets going and the rattle goes away it’s probably in the 40-50db range I suppose?
Note that AFAIK v2.1 does not change the fan but does add ramping instead of the simple off/on behavior from older models. I don’t know if it adds any hysteresis or PID or anything to keep the fan from ramping up and down all the time. One of the reviews probably covers that. The on/off definitely makes the fan more noticeable, but with the fan spun up there’s no two ways about it: it is loud.
Doing anything to reduce the noise is probably going to be a drastic change in some way. Adding a decent fan will make the charger much larger, and it’s already big.
Maybe replace it with a ‘smoother’ fan? But even if the fan is ‘smoother’ it still causes some vibration/ rattle. So maybe place the charger on a ‘softer’ surface while charging to minimize the rattle?
The Opus 2.1 fan does kick on and off quite a bit; however, mine isn't loud anymore when it's starting up and shutting off. I took it when new and packed it full of synthetic grease that won't separate and then removed the outer plastic case piece, which was distorting the fan housing on my sample. It is much quieter now, but still far from silent. Even after clearing the calibration jumper it still only charges to about 4.15v, but I'm OK with that for cells I use every day, since they'll last a bit longer. It still bothers me a little bit that it is the most expensive charger I own and yet isn't one that I would want to sell at my store, because out of the box it just isn't quite right--I wouldn't want to deal with all of the noisy and failing fans. It is an ambitious charger and I think that a lot of us would pay an extra $10 if the overall quality and accuracy was better. With a better fan and better accuracy and I think it would be a winner.
The fan on my Opus 2.1 is very quite with no vibrations or rattles. I put a PC fan underneath it and it rarely even comes on now. It sits directly on top of the fan and both are powered from an old pc psu so automatically power up at the same time.
If noise is an issue, or accuracy, I’d get a different one for certain, in fact I wish I hadn’t bought mine. The fan and smell are too annoying for me, I always use my other chargers…plus not charging to 4.2V is not ideal. The plastic or something they used on it kind of reeks, and when the fan goes on it spreads the smell too, just a bunch of little unpleasant things add up, and its ridiculous having a noisy stinky charger…
I’ve had it for a month and haven’t had any issues with it. I’ve probably discharged over 150 18650’s during that time and charged around 25 and it’s been rock solid. With the pc fan I have to look closely to see if the Opus fan is even running.
The only issue I have is that it slightly undercharges (4.16 - 4.17 depending on battery) but that’s within specs so it doesn’t bother me.
As I said I don’t use it because: 1) its noisy, 2) its stinky, 3) it under charged to 4.16-14 as I recall and 4) I have other chargers. Take away 1-2 of those and I’d probably use it, but for now, I don’t have to, so I don’t use it. I like the LUC chargers I got, they have a 2A charge option and I use 26650s frequently, but they also have a problem of over charging a little. However, for my 4.3V batteries, thats a bonus… I actually think I received a 2.0 instead of a 2.1 but… I still wouldn’t prefer a smelly noisy charger over a non smelly quiet charger
