UPS design

bassbindevil

Joined Jan 23, 2014
824
LOAD is just whatever you power from it.

It looks like the cells you're getting are normal lithium-ion. The fact that they have tabs already spot-welded to them suggests could be new surplus. Or they could have been rejected for being under-spec, or counterfeit. They resemble the real ones tested here, but I don't see the faint QR code marking, or date code stamps, so it might just be a good fake wrap. I'd be inclined to order one or two to test, unless you have some independent assurance that they're good. The different look might just be normal production variations.
https://lygte-info.dk/review/batteries2012/Panasonic NCR18650B 3400mAh (Green) UK.html
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,755
LOAD is just whatever you power from it.

It looks like the cells you're getting are normal lithium-ion. The fact that they have tabs already spot-welded to them suggests could be new surplus. Or they could have been rejected for being under-spec, or counterfeit. They resemble the real ones tested here, but I don't see the faint QR code marking, or date code stamps, so it might just be a good fake wrap. I'd be inclined to order one or two to test, unless you have some independent assurance that they're good. The different look might just be normal production variations.
https://lygte-info.dk/review/batteries2012/Panasonic NCR18650B 3400mAh (Green) UK.html
Yeah, tanks. I figure it out in the meantime
About the batteries, yeah, tey are probably some fakes. But it doesn't matter. For this purpose I just need tey don't leak or don't catch on fire on their own. If they degrade quickly, I still can use the BMS and the other device for other projects with real cells.
I'm now waiting on thhe items to get from Aliexpress.
Let's see how this will turn out!
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,755
Hi again.
I just got part of the components and I was trying to discharge some old batteries from a power bank I had here that was not charging (or at least wasn't holding the charge) with those power resistors. I got two of these. One is 5W4Ω and the other one is 5W5Ω.
I try to do it with the 5W4Ω. It got quite hot and at first I saw the batteries discahrging from 3.8V to around 3.2V but then, I measured again and it was measuring 3.71V and was increasing. Don't understand. lol. This was in about 5 minutes.

Now, I'm trying again with the 5W5Ω and it's measuring 3.55V and decreasing! Going to wait for 5 minutes also and see what happens!

Edited;
5 minutes later with the 5W5Ω, the voltage decreased from 3.55V to 3.177V
But the, I removed the resistor and measured again and it's back up to 3.63V and increasing! How is this possible?

Edited 2;
Further, I tried to use P = V*I <=> 5 = 3.72*I <=> I = 1.344A.
However, with the 5W4Ω, DMM shows 0.880A
and with the 5W5Ω, DMM shows 0.660A

I also tried P = R*I^2 for both Rs, giving currents of 1A for the 5Ω and 1.1180A for the 4Ω. Why any of these values match neither with the other Power formula nor with the DMM?
 
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PsySc0rpi0n

Joined Mar 4, 2014
1,755
Ok, peeps, I now have enough batteries to build a 4s3p battery. I also have the BMS and the other device (can't remember the name now).

I didn't remember but I had here 4 more batteries, however, they must have lost some charge over time and they are now all at 2.69V.
Is it ok if I use 2 of these cells with the other 10 cells at 3.6V? Will the 2 devices (electronic boards) control the charge of all cells even if they are not at the same voltage?
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,755
@bassbindevil I think I can use cells at different carge level but I wanted to make sure. I expecting the 2 electronic devices to balance the charge needed according to each cell / cell pair, no?
 

bassbindevil

Joined Jan 23, 2014
824
It's better to charge all the cells to the same level before assembling a pack, although if one bank is low, the balancer should eventually even them out. Also, to test the cells for capacity and internal resistance. For internal resistance, just touch a load resistor (say 4 ohms) across the cell and see how much the voltage drops from open circuit. Capacity requires a smart charger or (much cheaper) a discharge tester (from Ali/Ebay for a few bucks as a board and power resistors).
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,755
Well, I didn't have most of those tools so I just went with assembling the whole stuff. Started by soldering the 3 batteries in parallel and then the 4 rows of 3 parallels in seies. Then I soldered the BMS and all went fine. Then went for the other small module and soldered the BAT- to the BMS LOAD-, then when soldering one of the ends of the LOAD+, one of the BMS transistors simply blew up. The other end of the LOAD+ (on the smaller module wasn't even soldered yet). No idea why this happened.

I'll try to get my hands on a transistor and replace the damaged one and hope that it was only that component that blew up and nothing else. But it will take sometime as I don't have an electronic shop where I live!
Sad day!
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,755
So, I'm searching for replacement transistors for this BMS.
What these have written is A09 N03(N) xxxxxx where the 'x's can be different. For instance, one of the rows are:
A09 N03 EDL3A73, A09 N03 ECC1A52, A09 N03N xxxxxxx, A09 N03N CEK0554 and A09 N03 EDA4A22.
The third one I can't read.

But, from this picture, you guys can help me finding the correct replacement transistor, please?
1681406380448.png
 

Thread Starter

PsySc0rpi0n

Joined Mar 4, 2014
1,755
Hello.

I'm back to this project and I've replaced one of the transistors that blew up last time I was soldering the wires from the batteries to the BMS. I have soldered the points 0V, 4.2V, 8.4V, 12.6V and 16.8V. Nothing blew up this time. I still didn't soldered the other module.

However, I'm not sure if the following is normal. I'm measuring from 0V to any of the leads of the transistors and all measure 0V. Is this normal?
I also measured voltage across a few resistors and they also measured 0V. There is only one component that measures the 14.4V which is what it looks to me as a diode.
Is this normal?
 
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