Just starting out... is there something wrong with my Opus?

alim

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Dec 6, 2017
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Hi all. Pretty new to things. Bought 8 used laptop batteries off eBay, 9 cell 7800mAH so 2600mAH each cell when new. The guy said if I want he has lots more of these packs.

So I broke open the first few packs and cleaned up the cells. They all read ~3.68v on my DMM which I think is a good thing, correct?

Next thing I did is throw the first four on my shiny new Opus BTC-3100 v2.2 to charge them up. It stopped at 4.17-4.18, which I though was a little weird - shouldn't it be 4.2?

Then more weirdness, I took the cells out of the Opus and checked them with my DMM and they read 4.47-4.48v!! Yikes! Pop them back in to the Opus and it shows them at 4.17-4.18!!

Any idea what is going on? Do I have a bad Opus? Do I have a bad DMM? Is this normal behaviour?

The cells all say "SBPM4L6" on them, if that matters. No hint as to what the brand is...

Thanks!
Alim.
 
Yes, the opus is way outta wack! I would recommend you seeing if you can get an exchange on that opus. The opus is defunct

I would say the DMM is probably fine. Test it against a fresh Duracell C,AA, or such, or a 9V cell. They usually are shipped fully charged within a few tenths. I the the C cell is shipped at 1.6V if I remember correctly.
Another thing to do is probe the opus while it's charging to see what the voltage is at the contacts. If it says it's that high there and the opus is still reading low, the opus is definitely bogus
 
alim said:
Hi all. Pretty new to things. Bought 8 used laptop batteries off eBay, 9 cell 7800mAH so 2600mAH each cell when new. The guy said if I want he has lots more of these packs.

So I broke open the first few packs and cleaned up the cells. They all read ~3.68v on my DMM which I think is a good thing, correct?

Next thing I did is throw the first four on my shiny new Opus BTC-3100 v2.2 to charge them up. It stopped at 4.17-4.18, which I though was a little weird - shouldn't it be 4.2?

Then more weirdness, I took the cells out of the Opus and checked them with my DMM and they read 4.47-4.48v!! Yikes! Pop them back in to the Opus and it shows them at 4.17-4.18!!

Any idea what is going on? Do I have a bad Opus? Do I have a bad DMM? Is this normal behaviour?

The cells all say "SBPM4L6" on them, if that matters. No hint as to what the brand is...

Thanks!
Alim.

That is normal for the opus to stop at 4.17-8, annoyingly but if you charge all the same and test from there it doesn't really matter.
Another thing to note is the opus is generous with its capacity readings, around 10% more.

I would check with another multimeter that is known to be correct.
 
What DVM? A DVM with low voltage can also be way off so you need to get a 3rd or even 4th unit to crosschek it!
 
Trying to choose which one is incorrect without any other verification is like flipping a coin.
Do you have any friends with a Volt meter or a power supply of a known voltage?
 
Wattsup said:
alim said:
Hi all. Pretty new to things. Bought 8 used laptop batteries off eBay, 9 cell 7800mAH so 2600mAH each cell when new. The guy said if I want he has lots more of these packs.

So I broke open the first few packs and cleaned up the cells. They all read ~3.68v on my DMM which I think is a good thing, correct?

Next thing I did is throw the first four on my shiny new Opus BTC-3100 v2.2 to charge them up. It stopped at 4.17-4.18, which I though was a little weird - shouldn't it be 4.2?

Then more weirdness, I took the cells out of the Opus and checked them with my DMM and they read 4.47-4.48v!! Yikes! Pop them back in to the Opus and it shows them at 4.17-4.18!!

Any idea what is going on? Do I have a bad Opus? Do I have a bad DMM? Is this normal behaviour?

The cells all say "SBPM4L6" on them, if that matters. No hint as to what the brand is...

Thanks!
Alim.

That is normal for the opus to stop at 4.17-8, annoyingly but if you charge all the same and test from there it doesn't really matter.
Another thing to note is the opus is generous with its capacity readings, around 10% more.

I would check with another multimeter that is known to be correct.

This isn't normal for my 2 BTC-3100's. They both will charge to 4.2v but it is possible some cells won't charge easily to 4.2v.

Just yesterday I had 1 cell of 300+ cells that I recovered that didn't want to charge to 4.2v @ 500mA. It did hit 4.2v when I used my IMAX b6 charger at 1A but the Opus at 500mA couldn't get it to charge up to 4.2v. It even charged for 21+ hours so I'm guessing the cell is bad because when I just leave it hooked up to my multimetre, I can watch the vDrop in realtime.
 
I contacted the eBay seller I bought the Opus from and told them about the problem. They asked if I would take a video and upload it so they could see what I was talking about.

Here's the video I'm going to send to them:

Someone let me know if I'm doing something wrong here :)

And yes I agree, it's possible that the DMM is giving bad readings, it's just a cheapy one nothing great. I will test it and take a video of that too because I'm sure that is what they are going to ask next lol.
 
alim said:
I contacted the eBay seller I bought the Opus from and told them about the problem. They asked if I would take a video and upload it so they could see what I was talking about.

Here's the video I'm going to send to them:

Someone let me know if I'm doing something wrong here :)

And yes I agree, it's possible that the DMM is giving bad readings, it's just a cheapy one nothing great. I will test it and take a video of that too because I'm sure that is what they are going to ask next lol.

That's weird!! Too bad you don't have another device to test the voltage to have a 3 data point. I use my imax b6 for that.

Sounds like a bad Opus.
 
That's a good video. The only thing I would probably do differently is be a little further zoomed out so the wires from the DMM could be seen to make sure they weren't connected to something else. And I would also have the DMM connected to the the cell using alligator clips so it could show the difference between voltages live without having to take the cell out; even tho, I would still take the cell out to show the voltages don't change.

That's my .02 worth ;)

May you get it resolved quickly. We cant have builders down and out for the count :p

Ohh, and I have several of those types of DMM's. Internally they are the same as some of the ones that costs $25 or so at Home Depot or Lowes. They have the same electronic board inside. Of the 4 that I have and have tested, they were never more than a few hundreths of volt off (that is, .01 Volt)
 
Well I sent the seller the link to the video, they said they're going to talk to their supplier and get back to me with a solution (hopefully!).

Stay tuned!
 
alim said:
Well I sent the seller the link to the video, they said they're going to talk to their supplier and get back to me with a solution (hopefully!).

Stay tuned!

Your voltmeter has an empty battery. This will make it drop its internal reference, so it will read al random voltages.
 
Interesting theory! I will get a fresh battery and re-test. Thanks!
 
Haven't heard that one, but does make sense. When working with arduino's you need to have a stable reference to accurately read the sensors. So, yeah, I can see this one happening. I think I should check mine as well ;)


Wait, if you have 3 DMM's, and all 3 batts are low, how do you determine that? If all references are off by about the same amount, you'd still be left with misreadings. And can we trust the batt manufacturers prepackage fully charged batteries?? Hrm.....
 
Korishan said:
Wait, if you have 3 DMM's, and all 3 batts are low, how do you determine that? If all references are off by about the same amount, you'd still be left with misreadings. And can we trust the batt manufacturers prepackage fully charged batteries?? Hrm.....

Check your 110/220V wall socket , if it suddenly reads 190/310V AC or something odd like thatand there is no white smoke coming from al kinds of electric appliances in your house. Then your battery is empty.

J.
 
Is there not a "Battery low" indicator on those DMM's ??? Evenmine cheap thinghas one...
Or can we not trust eventhose? ;)
 
EV_BR said:
Check your 110/220V wall socket , if it suddenly reads 190/310V AC or something odd like thatand there is no white smoke coming from al kinds of electric appliances in your house. Then your battery is empty.

That's a good point. However, you can't tell how far outta wack it is as mains can vary in voltage by 20V or more. I have 120V split phase and voltage can be as low as 108V or as high as 128V (most of the time when I've checked). I'm sure the 240V mains in EU other countries could probably swing further than that.
But, I suppose, that's why we don't use mains to calibrate our DMM's :p
 
Could test on a couple of wall warts, if you get readings close to the rated DC output you're probably golden.
 
With a load resistor or while charging a device. As the wall wart will show two different voltages with or without a load on them.
 
Can you explain how I would do that please? I just tested my DMM against two 12V wall warts and the reading were way high, one read ~15V and one read ~18V. So ya I'm pretty sure I need to change the battery in the DMM.
 
The DMM battery is a 9V. Just pop the screw(s) off the back and drop in a new 9V. For load testing, you need to take a resistive load of some sort and connect it to the wall wart. Taking a paper clip with a slight bend towards the one end can help get inside the center core. Take an alligator clip and connect around the contacts. Take the other and connect to a light bulb (incandescent, not led as it might not have enough to drive the leds) or a 12V fan (like a computer case fan). These are sufficient loads to bring the wall wart voltages into spec.

The open voltages are high due to the nature of magnetic fields on the transformer. They don't use boost/buck converters in wall warts, but a small transformer, and it's not shielded at all, either.

Also, while you have the back off, you could do some calibration on the DMM. You'll see a resistor pot (looks like a flat head screw-like part soldered to the board). Turning this will adjust the ranges of the DMM. So, if you connect a device to the wall wart, and check its voltages, and it's not on point, then the DMM needs slight adjustment. Turn very very slowly, doesn't take much to adjust them.
To do that, I would recommend cutting the wires and resplicing them together so you have access to the wires and can connect the other end into a charging load (like a cell phone). This will provide stable voltage/current without alligator clips wiggling possibly causing misreadings.
 
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