I just got one too. I think it takes a lot of trial and error to use it properly. I had to use the OP instead of the user manual in an attempt to measure capacity of an Eneloop cell.
It was easy to set the mode CHARGE TEST (why not DISCHARGE TEST?)
In the right upper corner it said LI-3.7 ( I thought it should confirm a NiMh?).
The OP helped me choose 1A as I wanted 0.5A discharge (not in the user man.)
It charged up OK. During the discharge phase I pushed a little to the cell and the voltage display was all over the scale ( f.i. from 1.12 to 1.21V). This would certainly hit the end voltage a lot too early if it did not measure with switched off current. So I had to use rubber bands to press the battery against the terminals to read the “real” voltage.
Not very trustworthy, but with “insight use” I think it can be accepted. At least it did cost me less than 12$.
Have you tried LiIon cells yet? Both HKJ’s and mine read 0.05v high. Guess it’s my own fault for not reading his review in detail, but charging LiIon cells to 4.15v is pretty useless to me. In the past with other chargers, the voltmeter accuracy varied from unit to unit. Wonder if they are intentionally setting them low. Could be the trickle charging might bump it up over time?
So I can sort of assume the early version reviewed is probably the version being shipped now. I didn’t see any firmware version # displayed anywhere, so can’t tell.
I’m afraid I can confirm your worries.
I registered the end charging of a LG 18650D1 in the OPUS 100 at 1A with a Fluke DM across the battery.
It looked like this:
table(table#posts).
| OPUS (V)| OPUS (A)| Fluke (V)|
|4.170|0.400|4.117|
|4.195|0.225|4.143|
|4.200|0.180|4.148|
|4.205|0.137|4.153|
|4.208|0.098|4.156|
| FULL |0|4.156|
|after 15 min||4.152|
4.15V is fine for me (better than for example 4.22V),
I will not see difference in real use of my flashlights, ohhh!.. perhaps 30 seconds minus of runtime…… with 4.15V than with 4.2V really, not problem.
I’ve got one Opus BT-3100 that reads 0.03v low, so full charge is to 4.23v, but I find that fine for this charger since it drains cells pretty quick if left on the charger - can’t always time it to know when they are done, exactly. I frequently pull the cells off at 4.18v or 4.19v (really 4.21v, 4.22v). Many, many charges, haven’t noticed any issues on the cells. For testing, really want the cells at 4.20v at a minimum - not only for max DD output testing, but also for consistency of testing. 4.15v results in lower amps, always. The first minute of runtime is critical.
Got mine today and I’m testing it now. So far I like what I see. My opinion can change drastically
I ordered it May 27th, got today, June 7th here in New York from Gearbest. The tracking number was worthless. But hey, I got it super fast in perfect condition. I’m a guy who swore I’d never buy from Gearbest again. Since they were the only seller who had them, I took a chance, and it paid off.
What I’ve noticed so far is the discharge resistors run fairly hot while discharging well used Panasonic CGR18650D I bought from The Reverend here on BLF in 2011. The internal battery resistance measures 91 milliohms according to the display.
Edit: Mine has a bad USB port. It outputs 3.88 volts with just the Charge Doctor connected. Less than 2.5 volts with .38 milliamp load. As you can see, my Panasonic 3400 mAh 18650 is fully charged showing 4.187 volts. Got in touch with gearbest a few days ago. So far they haven’t responded.
I received mine from gearbest and i like it but there is a slight problem with 16340 cells. It seems that there is not enough tension or contact for 16340 on my copy because it shows 0.2V most of the time, when you move the cell a bit it shows 4.10V and only in a certain position it shows “full” when i insert a fully charged 16340. That is not ideal becaue the ideal position is nearly impossible to reach. I will use it only for larger cells because i dont have the problem with 18650s.
I also received the Klarus C4 from gearbest and the blue power LED is flickering all the time, i guess it wont affect the charging but still not nice.
That is a problem when evaluating chargers, my minimum length specification is with very low tension. I.e. the caliper has connection to both + and -, but there is basically no tension (There is a very low tension). I would like using a value with higher tension, but I cannot see how to do that reliable.
with 4.15V than with 4.2V really, not problem.