The Opus 3100 is well known for not charging batteries to 4.2v and showing higher voltages on the display. There was a long running thread in BLF when it first came out that ended in the Opus engineer (Henry) responding and saying that that was an intentional design.
However, there was a way to change that by removing the bottom cover and either opening or closing 2 contact points. Sorry, I don’t remember which and it wasn’t a matter of flipping a switch (although there is one to have it charge to 4.2v, 4.3v, or 4.35v) and required the use of a soldering iron.
I did some brief Googling to see if I could find the thread but wasn’t able to. Perhaps someone else remembers that thread and can point to it.
Anyway, it’s not surprising that the OP’s Opus terminates at less than 4.2v even taking into account the voltage drop after it stops charging.
Yes a good dedicated cylindrical cell charger is much more convenient. Especially if we charge lots of cells.
But you need one that works properly. If you can handle the price, the best one that I have found is the SkyRC Mc3000.
You seem to enjoy tweaking things. You can adjust about every charging parameter with the MC3000 and calibrate it as well.
As to resting voltage, I am not sure why we are seeing the differences that we are. Maybe the meters used for testing (?) But it is rare for me to see a cell that will measure 4.19 V after half an hour or more of rest after charging. Even brand new (date code of 2 months or less since manufacture) cells. Most of mine are 4.16 to 4.18 volts. This is charging to 4.2 volts with a termination at 0.150 Amps . I don’t worry about it, because the difference in capacity of a cell that rests at 4.16 versus one at 4.18 volts is miniscule. Many people will charge to lower voltage (~4.10 volts) simply because it adds cycles to the life of the cell while not losing much in capacity.
BTW If you get a fully and properly functional Opus 3100, it will do a good job for charging your cells.
Its a good charger. No not perfect,but mine has been pretty much flawless. The next step up is the SkyRc MC3000 at about $120 (about 2.5x the price of the S4+). If you don’t need all the fancy features of the MC3000, I recommend the S4+. It had been upgraded from the first model, and if you get it off Amazon, it’s guaranteed to be the latest version. I like it because it can charge my 5500 mAh 26650 and 21700 batteries at 0.5C which is an acceptable charge current, and my high drain 21700s at 1C on all 4 bays, which is also an acceptable charge current for modern 21700s. The iR measurement is about 50% high (consistently) and the Opus and MC3000 are “in the ballpark” with iR. There’s no truly accurate iR measurement with hobby chargers. You need a standalone tester for that since measuring iR requires certain parameters to be met for accuracy…cell mfgs do it on AC, not DC and at certain voltages. Also, cell termination voltages vary across chargers based on accuracy of the voltage. Most are within +/- 0.5 to 2.5 volts. The S4+ consistently terminates at 4.17 to 4.19 volts and doesn’t seem to trickle charge. A fully charged li-ion battery is between 4.16 to 4.19 volts and consistently charging them to 4.2 volts can decrease their lifespan, so it’s not bad to have a charger do that. The different in capacity at 4.17 to 4.2 v is negligible.
I’ll see if I can find the information I’m interested in thanks for the heads up!
But it has come to me with warranty seal on the screws that gives me that it is a clone since the original did not carry it.
I have been looking at it and I like it as I think it can be calibrated and I have instrumentation for that.
In the end it is not expensive since this one has cost me 38€ the other one is worth three times more but if they do not solve it I will keep it in a drawer and buy another one, that is to say I will pay twice as much.
I like the S4+ I saw it but don’t trust the brand.
But I would like to know if it leaves the battery at 4.19v if you could measure it would appreciate it, but not worth a tester of those cheap AliExpress as it is little variation in value and much in real information I do not know if I explain.
My measurements are real as I said I used a professional tester, the problem is not loaded to 4.16v or rather to 4.164v
The problem is, it measures much more, and does not load any cell that is close to 4v because it adds more than 0.2v, so a 3.9v cell could not already load it full and 4.22v!
I can only charge batteries below 3.9v
It’s clear that this charger is calibrated very high or is defective.
Then I measured the load intensity because I read it in a PWM review if you charge below 2A gives a square wave that I measured from 2A peak! imagine a small battery of 850ma you put it to charge at 400ma because I send pulses up to 2A that is a great stress for batteries, I don’t have batteries of that kind may be lower.
If you have this charger, the good batteries batteries don’t charge them unless you do it to 2A.
Beware of it because you’ll charge the batteries soon, the data is there, these things are not seen with the eyes are seen with measurements.
Lii-500 doesn’t do that. It’s linear. It doesn’t stick peaks. It doesn’t use PWM to vary load intensity.
But it measures the internal resistance very badly and only charges liion batteries and the normal 1.2
Here’s the fix to the problem if your Opus is reading higher than what it really is. I couldn’t find the BLF thread but this pretty much covers what needs to be done.
Basically the J1 jumper is what needs to be tweaked.
Ok found the BLF thread that talked about the voltage discrepancy plus other issues with the 3100. Start reading around post 325 for pics and other stuff related to the low voltage fix.
The 3100 is clearly broken. If you want , you can try some of the links above. But I would push for a full refund.
BTW, I agree about the MC3000. People always point out the cost. But if you can use and need all of its features (including data logging using a PC). It is definitely worth that cost. Besides, the firmware is fully developed (they worked closely with the folks at CPF over a few years to squash pretty much all of the bugs and to add valuable features).
AND mine is still working fine after around 10 years of heavy use.
Obviously, I am a fan. Last time I saw it for under $100, I bought a spare.
My Opus is more than 6 years old. It still works great . I’ve charged thousands of batteries and done hundreds and hundreds of capacity tests on it.
It Always gives a Full charge of 4.20 volts unless they’re old batteries with high internal resistance. Regardless of the end voltage it always matches up exactly with my DMM.
I really don’t have any pictures of it when the charge is complete. 99% of my photos are capacity tests.
Yup, but it is not the one that @litris is using…and it is not a version 2.2.
Glad it is working for you though.
BTW, my ~5 year old unit work OK too (still overwhelmingly prefer the MC3000 though).
Maybe they just made the newer ones “better”…
Or his is just broken. Yours and mine working, doesn’t fix his problem!
He mentions in the OP that he is going to get version 2.2. ??
That’s what mine is. I don’t recall an upgrade in the last 5 years. Maybe his is counterfeit? I went through the thread and I didn’t see anywhere else where he mentioned what version he had other than his original post.
The seller has given me a proposal to refund me 0.02€ I have rejected it and I have put that I do not want it but I have not put return of the item because sending this from Spain to China is worth twice the price of the charger!
Thanks for the comments my charger does not charge me any battery.
They have to be very discharged if it does not start charging.
My batteries are at about 3.9v 3.8v and the charger marks 4.19v, 4.22v and does not start charge, the seller returns me incredible 2cts.
I already knew it was risky to buy these things at AliExpress I bought a lot but the measuring stuff and in this case you should buy it from local shops or reputable internet sites.
Here you get a lot of forgeries, so I only bought batteries once and they were fake, now I buy them in physical stores in Vapeo and wanted to buy online at NKON but I asked for advice on a battery and I was warned about a 30€ battery or more and protected that I don’t want to do what I want.
Clearly this store looks at your interests. It’s logical to make money, but they should be more honest and lost a buyer.
I just had to be advised an EVE a 10A download Novicel or the Samsung 30Q I don’t know if that was it.
Instead they went directly to sell me the most expensive of your catalogue without looking for the use I explained to you warning without protection.
The shipper is clearly damaged I don’t know what this seller will ever answer before or after a week just before the end of the AliExpress deadline answers that it returns €0.02
About NKON, what do you think?
Can I trust you?
They never contacted me again.
I don’t see another one on the Internet for Europe or if you know about another, if I don’t keep buying locally, higher price is sometimes twice as much.
Looks like he was right is expensive, the Opus charger and the MC3000 cheap.
Because if I don’t get the return I’ll have 38€ in a drawer and spend another € 38 or € 40 in the end I’ll have paid € 30 less than the MC3000 but I didn’t know it I saw it above it was the brand of the RC devices I bought and never sold chargers and I didn’t keep looking.
See what happens and I already decide to use my calibrated RC charger or buy one from a cell for four times a year that charges the batteries or directly the MC3000.
MC3000 I like what I read here but I have to see a review.
Then see if it’s worth paying for the MC3000 to use it about 4 times a year only on holidays and in rally competitions only the stretch that is done at night.
Thanks to everyone, I’ll inform you, but lately AliExpress is not doing very well with buyers shipments that do not arrive returns etc.
I noticed difference now. The writing in the bottom right corner is different. Yours it starts more towards the middle of the charger below display and mine starts on the far left on the other side of mode.
