If your Opus BT-3100 charger is reading 0.05V higher on the display than reality....

jm1

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Dec 14, 2017
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Hello Guys,

I have a couple of Opus chargers, one of them was consistently reading higher voltages than the other. For example, my cell would read 4.19V on my Fluke multimeter and also on one of my Opus chargers. If I popped the cell in the other Opus it would read 4.24V which was not reality. This caused all cells to start the discharge cycle from 4.15-4.16v since the display showed that as 4.20V.

I opened the back of the charger and desoldered the J1 jumper which is described as a "voltage compensation" by the Opus manufacturer. Once I did this it now reads accurately and matches the |Fluke meter as well as the other Opus charger.

Just putting this out there in case anyone else notices this 0.05V higher voltage reading on the Opus display.

James


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I wonder if this could be one of the reasons it reads consistently about 10% off on capacity tests. Perhaps instead of leaving it disconnected, put a POT on there instead so it can truly be calibrated accurately.
Wonder what else can be so easily be fixed with these things.
 
Korishan said:
I wonder if this could be one of the reasons it reads consistently about 10% off on capacity tests. Perhaps instead of leaving it disconnected, put a POT on there instead so it can truly be calibrated accurately.
Wonder what else can be so easily be fixed with these things.

A POT might help, right now it seem to be reading within 0.01V of my Fluke so Im pretty happy now. I did some extensive Googling and found info online from 2014 about the J1 jumper needing to be desoldered if the Opus reads pretty much exactly 0.05V over the real voltage.
 
Perhaps you can do a test of a known cell and see what it does with and without the jumper in place. How far off are the capacity readings.

Would be interesting if that is the sole reason for it being off. Something everyone with an opus could do as a permanent mod to get it more accurate.
 
I just returned one because of that. The replacement isn't any better, it's .03v off, which isn't so bad, but the big thing is that it charges and discharges much slower than my original unit. It's about 20 mins longer. Hope this might have something to do with it.
 
Both 0.03 and 0.05 is within what that device can do :p Its cheap of a reason but with that said you can tweak it a bit but it wont do that much on capacity since its already showing to high capacity to how it measure.
 
daromer said:
Both 0.03 and 0.05 is within what that device can do :p Its cheap of a reason but with that said you can tweak it a bit but it wont do that much on capacity since its already showing to high capacity to how it measure.

In my case I made the change so that all my Opus chargers are reading the same or extremely close to the same which is now the same as my calibrated Fluke meter.Having one charger with a constant 0.05V difference was making a difference in the mAh rating I was writing on each cell out of this charger because of the fact that it started its capcity test when the real cell voltage was only 4.15-4.16 instead of 4.20 as the other Opus charger was doing. The means all cells from one Opus charger always had lower mAh values compared to running those same cells on the other Opus charger because there is more mAh to be gained from 4.15-4.20 then there is at the bottom end 2.75-2.80.

So now they both read consistently high ::)ut at least I can separate my cells by mAh properly.
The info on desoldering the bridge at J1 came right from the designer of the Opus charger, many owners discovered this exact 0.05V difference and he said "desolder the J1 jumper".
 
Mine seem also to indicate values higher than normal, since cells charged with different chargers when put in for discharge tests show voltages of 4.23. I will test this with my Extech to be sure.
 
On one of my Opus chargers I measured 4.19V with my DMM while the Opus itself said 4.20V. (the J1 is connected)
I'll test the other one after the DC-Test is done.
 
Yep they definitely are not the perfect Voltmeters out there. :D


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Wolf
 
So where might a pot got to dial in the voltage? I bought some small ones months ago but never got as far as figuring that out.
 
Well done James!
 
All Opus users need to know about J1 --> inside the Opus is a labelled solder bridge on the PCB which substantially (60-70mV?) alters the voltage sense on all slots. Cheers jm1 for starting this thread, with pictures.

If it is open, it reads low[er] which is optimal if you want the cells to be recharged AND topped off by the Opus. If it is closed, it reads lower on all slots, which is optimal for testing cells, as it doesn't 'hang' on (try to top off)cells which are 'only' 4.16-4.19V, it just gets started testing (discharging), as it thinks they are 4.22V already.

All of mine now have J1 joined. I think it matters far less which way you set yours up, so long as they are all set the same.

Do not assume that if you order two at a time that they will be the same out of the box. Mine weren't.
 
All Opus users need to know about J1 --> inside the Opus is a labelled solder bridge on the PCB which substantially (60-70mV?) alters the voltage sense on all slots. Cheers jm1 for starting this thread, with pictures.

If it is open, it reads low[er] which is optimal if you want the cells to be recharged AND topped off by the Opus. If it is closed, it reads lower on all slots, which is optimal for testing cells, as it doesn't 'hang' on (try to top off)cells which are 'only' 4.16-4.19V, it just gets started testing (discharging), as it thinks they are 4.22V already.

All of mine now have J1 joined. I think it matters far less which way you set yours up, so long as they are all set the same.

Do not assume that if you order two at a time that they will be the same out of the box. Mine weren't.
Greetings to all!

Sorry for refloating the post I do not know if it is allowed.

I have a newly purchased Opus BT-C1000 and I can not charge any battery because it marks between 4.20v to 4.22v thinks they are charged.

With a Fluke 177 tester the measurement is 4.17v or 4.16 depending on which one I use.

I can't modify it because it has a warranty seal on a screw.

I am in an open case on AliExpress and the seller never answers before I buy it or even answer the AliExpress department.

My doubt is that it is commented that it is good for the discharge that measures less than the real thing but as it was not put to load I tried to unload.

But it turns out that for the Opus is 3.0v the real measurement is less than 2.8v and that's bad if the discharge is greater I stopped it before so that it did not go down more and average almost 50 ° at that point also measured with professional instruments.

Does the modification work well both ways?

Is there any way to tune further by changing some resistor instead of the bridge.

I saw it in a post on the one bay model.

This way I could calibrate it better to 4.19v like all my chargers or 4.20v.

Thank you.
 
I have 4 x OPUS BT-C3100 chargers and they vary as much as 50mv between each other. In fact I have an "Add 50" label on one of mine.

You mention 4.22v -> 4.17v and when I charge my cells via OPUS they immediately drop to ~4.17v range after full charge - this is normal using OPUS for full charge with18650 chemistries.

As far as 2.80v vs 2.75v ... not sure that's a critical issue.

And the IR reading is notoriously useless for any accuracy - can only be used as a 'very general' guide.

When I process cells to build a battery, I take OPUS capacity tests to be useful at the 50mah +/- range. When testing groups of cells I put them in 100mah buckets - e.g. 2100-2199mah(s) in 1 bucket, 2200-2299 in next bucket, 2300-2399 in next bucket.... and then evenly distribute them thru the battery.

Sounds like you're expecting a 'more precise' performance from OPUS than I would expect but perhaps they can be calibrated as you suggest :)
 
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Same here, I use LiitoKala 500 chargers and one of my units stops charging at 4.16-4.17V. But knowing that I adapted my procedures (on each cell I write the charger number, and charger number 3 is the one with an important offset). I have no intention of opening it and trying to find a solution! I mean, I paid them 15€ (around 15$) each...

Having the jumper is a great thing, a pot regulator would be even better. I suppose it shouldn't be difficult (or it might be!) to make such an extension to the Opus.

I am in an open case on AliExpress and the seller never answers before I buy it or even answer the AliExpress department.
If the seller isn't Opus I don't think they can do much about it because it's a "feature" (bug!) of the device. You can return the product if you don't think it's good.

As OffGridInTheCity says, as soon as I remove the cells from the charger, when they're full, there's an immediate voltage drop.
 
If the seller isn't Opus I don't think they can do much about it because it's a "feature" (bug!) of the device. You can return the product if you don't think it's good.
Sounds like you're expecting a 'more precise' performance from OPUS than I would expect but perhaps they can be calibrated as you suggest :)

I do not receive notice from the forum!

Thank you for replying, the seller did not answer, neither did he answer Aliexoress and I won the dispute.

With 2 options.

Return to the seller and the seller pays the shipping costs, but with one condition, contact the seller and accept the value of the shipping costs ( three times more than the value of the charger ) did not answer and if I did not answer I could not select this option.

The other option was to keep the charger and I was refunded 9€.

I lost all the value! I chose the 9€ option because the other option was to pay the shipping costs and the seller would return it to me but he never answered!

I have tried with the bridge and without the soldered tip.

It didn't help.

Without the jumper, it loads well above 4.21v and with the jumper 4.17v I left it like that and saved it doesn't give me much confidence.

Maybe I will use it just to see the IR and capacity.

I still charge with Diy circuits and RC charger calibrated with the Fluke is very accurate.

I tried a variable resistor on the bridge and it didn't work, that triggers an input on the mic that makes a correction.

Thanks!!!
 
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