I got mine today , thank you HKJ for this incredible review it really helped me much
but i have a question what is the benefit of the discharge refresh that Discharge and charge the battery 3 times.
Most NiMh and NiCd cells do not achieve full capacity until they have been cycled a few times, so it makes some sense to use this feature on new NiCd or NiMh cells. Cycling a Li-Ion just reduces the life expectancy, so this feature is pretty useless on Li-Ion cells.
Can a DC adapter be used with this charger and is there one specific to this charger available?
is there is any hint or advice on using this charger to test cells capacity ?
Mostly you will use the "Charge test" function for that, where you select a current close to the one you expect to be using the battery at.
Hi HKJ (or anyone else that can advice) -- I just got my v2.1 version and still have a v2.0 version. The v2.0 version always read LiIon cells low, by 0.03v, so it charges up to 4.23v. Of course if you don't catch it right away, it discharges the cell, so the cell may be 4.17v by the time you take it off.
For the new v2.1 version, it reads LiIon cells high by about 0.06v. So, it reports a cell "FULL" charged when it's really at 4.14v. I know these cheap chargers can't seem to be accurate for voltage, but this is a big margin of error, and for my usage, unacceptable. I'd have to move the 'charged' cells over to another charger to top off, and it won't just be a minute or 2.
These two Opus chargers seems to be the most inaccurate chargers I got. The NiteCore and JetBeam i4 chargers I have are more accurate, within 0.01 - 0.03v.
I just went through this review and following posts, and can't find any mention of the accuracy, though probably missed it. Think you mentioned 0.01v, but not sure if that's the resolution or accuracy. Let me know what you think -- thought I read some detail posts about these charger's reported voltage accuracy, but can't find it, and I think the 0.06 to 0.07v delta is too much.
I do not know how you measure the voltage, it is a bit tricky to measure precise.
When I specify a precision on the voltage readout it is compared to one of my Fluke or Agilent DMM's and measured when the charger is not charging (if possible). Next copy of the charger will probably have another tolerance and a slightly different error in the display readout.
For actual charge result you can see my curves, the scale has a very good accuracy.
There will always be some tolerance on the voltage in a charger, usual I do not talk about when it is within +/-0.05 volt (The allowed tolerance for many LiIon cells).
Ohh - I do it off the charger on the bench with no load, using a Fluke DMM or other DMMs - the DMM's seem to be consistent with each other. With the Opus chargers, it's easy - measure a cell on the bench with the DMM, pop the cell into the charger and see what it reads.
Oh ok, I see now where your voltage curves end - looks like every single one is at or under 0.01v accurate (4.19v to 4.21v). So that voltage is not what's reported on the charger, but rather separately tested? If so, it seems like your charger is much more accurate than my v2.0 and v2.1?
That will work.
When charging I do not use the display to check the voltage, but a logging DMM. On this charger it will show a higher voltage than the display on the charger while charging. This is because the DMM measures the average cell voltage and the charger measures voltage with current off.
I do not know if the charger uses the same reference for charging and voltmeter (I would expect they do).
My copy of the charger was very accurate both in display and while charging, but I will not expect all copies of it to be that accurate.
Thanks. I'm opening a ticket with GearBest and going from there. Though it was a great price with the GB deal, it would be a huge PITA to use this thing this way. Just wish there was something adjustable to fix it - rather do it myself, but dunno enough bout it - probably a resistor swap somewhere...
Just took a KP 14500 840 mAh cell off the Opus - read FULL at 4.20v. Tested with no load on the Fluke DMM and it says 4.13v -- hhmm, pretty consistent in the 4.13v or 4.14v range.
I have 2 - v2.0 and 1 - v2.1
If I take a cell and measure the voltage with a DMM, Then place it in the charger, in all cases the measured voltage is within 0.02v. This is true for both Li-ion and NiMH.
Could it be what you are describing is the measured voltage on the OPUS after it has finished charging and as it had time to sag would measure less on the DMM? What happens when after you take it off and measure with the DMM, then place it back in the OPUS. What does the OPUS say the voltage is then?
EDIT: I just checked my OPUS and it DOES continuously update the voltage of a fully charged cell sitting in the cradle. I just charged a TrustFire 14500 that is a very poor performer (250mAh) and it charged up to 4.20V. 15 minutes later, while sitting in the cradle the OPUS was measuring it at 4.07V. Then I took it off and measured it with my DMM, it was 4.06V
Had I charged it to 4.20V and took it off and measured it 15 minures later, I might be led to believe that the OPUS only charged it to 4.06V
Yes - I'm quite familiar with the parasitic drain of these things - it's pretty bad. I'm comparing what the Opus reports as the voltage level, compared to a DDM - just like in post #47 above. If you take a cell, check it on the DDM, then put it in the charger and check what the Opus reports, it's off by 0.06 high usually on the v2.1, and by 0.03 low on my v2.0. Of course this means the Opus 2.1 is under charging all my cells.
If yours is always within 0.02, then you got a decent one I guess. I got a NiteCore i4 and a JetBeam i4 as well. The NiteCore is pretty much dead-on, while the JetBeam seems to be low, just like my Opus v2.0 - fresh off the charger the cells measure 4.23v. I like using the 4.23v cells - my lumens/throw #'s seem to like it 
. Might be more wear/tear on the cells though...
I believe that you are misunderstanding the result. When a battery has been charged the voltage will drop after the charge stops, this has nothing to do with parasitic drain, but is related to the chemistry in the battery and how it is charged.
ok - just acts that way. I don't see the drainage in the i4's, just the Opus BT-3100's. To me, this is a really bad feature for a home use charger because I can't babysit the charger, and not sure how to calculate an approximate time they would be done. I'd assume it's because of the design of the chargers?
Edit: Just took an old IOS 14500 840 mAh cell off the Opus 2.0 (FULL). The Opus 2.0 says 4.18v. Dropped it into the Opus 2.1 - it says 4.28v. The Fluke DMM says 4.21v -- this is just too far off.
The C3100 drains about 4mA in current, i.e. even 10 hours (40mAh) is not going to drain any significant capacity from the battery (The i4 will continue to charge with a small current).
Batteries will usual drop between 0.01 and 0.05 volt, just because the charging stops.
Thanks HKJ for the explanations. Forgot bout the i4's continue a slow charge rate. I left a couple new cells in the 2.1 overnight for a discharge test, and taking these brand new Panasonic BD's out of the charger in the morning and checking on the DMM, they were at 4.11v. Between the 0.06-0.07v error, and the continuous drain I guess, resulted in this. Not sure how to quantify the 10 hrs of 40 mAh discharge, but I'd guess between 0.02 and 0.03v, maybe.
Yes, that is why I chose a really poor quality cell, the 250 mAh TrustFire in my test, to exaggerate this effect.
If that is what it is then I wouldn’t be happy either.
No - one unit is off by 0.03 (old one) and the other is off by 0.06v to 0.07v (new one), as I listed. The Fluke is as accurate as my $15 DMM - no better. I expect more from a $65 charger.
Ok - I'm getting tired of repeating myself. That's is for me here... Shame one piece dead-on accurate unit is given to the independent tester by the manufacturer... So much for the rest of us...
And where was that tolerance spec on the website listing? Why are $10 chargers more accurate? Why do cheaper chargers keep the cells charged after the charging cycle is complete while this expensive charger drains them? I don't buy the excuses.
I havent liked this charger since day 1. Partly because of the way they attempted, successfully to some degree given the number sold, to use HKJ as a crutch to sell units while out the other side of their mouths dismissing his concerns over the charger as almost trivial at times. The revision versions failing to address all concerns, and those it did were not so much corrections as they were ‘fixes’. It just never felt right to buy one so I bought a VP2 instead.
Even at 0.05 tolerance, 0.06 is out. Im betting some folks probably think its only just out so no biggie, but its out past the amount its quietly stated it might be out. A tolerance, plus some more tolerance makes no sense.