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TP4056: Is the series shorting problem fixable?
#11
Well, I still can't find any isolators that will do what I need. The B0505S could work, but I'd need 5 per board to get the full 1A. The project I'm thinking of, I'd need 210 of those. So I'm looking at the individual power supply route. 
I could buy a wall charger for each TP4056 board. Or maybe get AC to DC converters instead. I found this one on Bang Good.

I suppose another option would be to build my own. Seems they're made of a transformer, rectifier, and a capacitor. And a regulator too, I guess. I'm not having any luck finding transformers though.

Is it the rectifier that isolates the ground?
-Mike G
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#12
I think I finally have an answer. Been watching tons of You Tube videos and reading Google search results. If I understand right, its the transformer that isolates things because there is no connection between one side and the other. Just a magnetic field. So the key to isolating each TP4056 board on a series battery is to power each one separately with some kind of device with a transformer in it.

If that's true, then a single power source supplying individual voltage reducers would work. As long as the voltage reduction is done by a transformer for each TP4056 board. I guess FETs are sometimes used to do the same thing. I haven't got as far as learning about those yet. As long as each board needs its own transformer though, it seems more practical to just get some kind of converter for each board that is powered directly from a wall outlet.

I have been having fun though, learning how AC adapters actually work. There's this great video series on You Tube by Afrotechmods That explains things pretty well. I still get lost a lot during his videos, but that's my fault not his, LOL.

Anyway, if I'm wrong about the transformer thing, please, someone tell me. I'll be buying some parts pretty soon to see if the practical application actually works.
-Mike G
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#13
Don't forget that transformers only work with AC not DC.
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#14
Thanks, I missed that! I've removed my bad example above for the safety of future noobs like me who might read it. Smile

Is that why FETs are used to reduce voltage? Because they work with DC?
-Mike G
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#15
FETs are used in many ways but in the case of a DC/DC power supply that uses a transformer, the FET is used to rapidly switch the DC to the transformer on and off (with a PWM signal) turning it into a kind of AC. So you now have a changing magnetic field and that is therefore able to pass through the transformer to provide power that is isolated from the source.

When there is no requirement for isolation, a large inductor is generally used instead of a transformer.

I don't know much more than that about it. I'm just interested in the general theory of such things rather than any in-depth knowledge.
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#16
A pair of FETs work in conjunction to turn DC into AC and then pass that through the transformer. Afterwards, the output is then passed through a bridge rectifier and a smoothing capacitor is connected after that to keep ripples out of the line.
If you were to drive each TP with this type of setup, you would only need enough FETs for the overall current input. Kinda like connecting them all to a powerstrip. Then, each TP would get it's own dedicated transformer/rectifier/capacitor to power it.
This does seem like a lot of extra work. I'm not sure how much it would cost to do all that, as well. The transformers wouldn't need to be very big, but you'd still need them. Probably the little round ones would be sufficient.
Or, if you can go to a local salvage store or good will or something like that, you could buy (or get free) a lot of wall warts. We have a local store called the "Repuprose Project". They take in loads of donated items and sell them as a non-profit. I've grabbed several things, take it to the counter, and ask how much. They ask me how much would I give for it. Almost every time I've asked for a price, I get the "Well, how much do you think it's worth". So you could see about those kinds of places. That is, if you really wanna go the wall wart method.
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#17
Well, I was mainly just curious about the FETs. I looked into building my own AC to DC converters, but the components I'm finding seem to be more expensive than the ones already made. I think those converter boards I found on Banggood are the way I will go.

I'm not sure how to explain this, but I'm looking at the connections, and they seem like they could be done up like a balance cable. Since the negative on one series is also the positive on another. Running two wires to each TP4056 board seems redundant. So I'm thinking I could wire it up this way:
[Image: b74b34279b33eafdc4ed88d2dd195a0e.jpg]
-Mike G
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#18
that might work. as long as the power leads are isolated. The balance leads is good, cuz that's how it's done (another youtuber did it that way).
Now, I do wonder, could it be possible to use 1 PSU per 2 TP's and use the 5V regulators and a couple diodes to each board to keep them separate. That part I'm not sure of. I don't know if the diodes would be enough protection. Probably wouldn't work, though.
The reason for the diodes would be to keep Neg and Pos separated. The reason for only doing 2 TP's at a time is because the diode has to be matched to the voltage. If the voltage goes to high, the diode will fail as they have a certain reverse voltage limit. Again, in the end, I dont think it'd work, though. Unless there's something extra that could be added to help out.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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Certified 18650 Cell Reclamation Technician
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#19
I found this fellow's video, and he's doing almost the same thing I have in mind:



You can see the common wire he's got between the -out on one board and +out on the other. Although, his project is a bit more complicated than mine.

I've gone ahead and ordered a few parts to start trying this out. I meant to buy the 1A converter, but bought the 2A by mistake. Should do pretty much the same thing, but the 1A units are about half the price. Good thing I started with only 2, LOL.
[Image: 3b18ef61fb64fe33feff593c8c7f6d74.jpg]
To my semi-trained eye, there are 1, maybe 2 transformers? Not sure what that black thing with the copper windings is. Inductor?
Anyway, there's also several capacitors, an IC, a FET maybe, and I think the red rectangular thing is a relay. And lots of diodes.
On the back there are lots of those tiny surface mounted resistors and capacitors.

Here's the description:


Quote:[b][b][b]Descriptions:[/b][/b][/b]

The power supply is isolated industrial grade built-in power module with temperature protection, overcurrent and short circuit full protection .

[b][b][b]Features:[/b][/b][/b]

AC85 - 264V or  DC110 - 370V wide voltage input
DC5V(+/ -1%)  2A isolated output
Input Current: 0.5mA/115VAC  0.25mA/230VAC
Input surge current: 10A (230VAC)
Frequency range: 47-63Hz
Operating Temperature: -30 - 70 ℃
Relative humidity: 20%- 90%
Rated power: 10W
Output efficiency: 75%
Module size: 6.6*3.0*2.2cm

While I'm waiting for Banggood's super (not) fast shipping, I'll do a mock-up with some TP4056s and some spare phone chargers I have around. Hopefully I can find a couple that are around 1A, or at least 800mA. I've found that the TP4056s happily take whatever current they can get up to 1A as long as the voltage is correct.
-Mike G
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#20
First off, to put youtube videos in, its:
Code:
Convert: [video=youtube]http://youtu.be/i8_XV5Yn7_s[/video]
To: [youtube]i8_XV5Yn7_s[/youtube]
You take just the last portion of the url and use that between the youtube tags. Unless you're putting the URL in, then don't put any tags in. Just past the link in your comments. Plus, you had dbl 'http://'. If you're pasting it using the video link button in the composer, make sure to remove the existing http:// that's there. It doesn't get removed automatically.

This Line Updated: He fixed it Wink

The big yellow is a transformer. You can see the Fet to its left. I'm assuming the fet goes to the transformer. The diodes to the right change it back to DC. The blue caps are used for smoothing the ripples and keeping the voltage balanced.
The Brown cap on the left I'm guessing is just to keep the input power stable in case of the output has a sudden draw.
The copper windings below that I think is an isolator. It looks to have about the same number of turns on both sides of the center plate. Red thing below is a relay, 250V 1A max.
Below the blue thing (is that a cap as well?) looks like an opto-coupler. I can't read the numbers on it, so not sure.

I might actually be getting better at circuit diagrams  Smile *please don't let someone pop my bubble Tongue *
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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Certified 18650 Cell Reclamation Technician
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