TP4056: Is the series shorting problem fixable?

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May 25, 2017
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I've read all the treads I could find here relating to TP4056 charging boards, and many mention this issue, but I haven't found a solution.

Specifically, I mean that if you have a battery, say 3s, and you want to charge it with 3 TP4056s you have to isolate the grounds or you get a short and melt the boards.

One solution is to use a different power supply for each board. I'm not sure I understand that, since each power supply would have the same AC power source, ie, a wall outlet. Or is the conversion from AC to DC enough to isolate the grounds?

Sorry, I'm an electronics newb, so I still don't understand a lot of what's going on.

Here's a diagram of what I would like to do:

image_vfceyt.jpg

So as long as the cells in the diagram are Not connected things work fine.
But as soon as the cells are connected in series, there is a short across the black wire on the TP4056 in side?
Is there a way to isolate the charging boards without using separate power supplies?
 
Yes, there are isolaters that can be used to separate the boards powersupply. But the part costs >$5 for each one. Since you have to either separate the charging powersupply, or separate the cells, you could have it so that when power is applied to the charging side, mosfets disconnect the cells from each other. When power is pulled, they reconnect. Now, this would also mean that 1) you can't use the cells during charging at all 2) there'd have to be traces from cell to cell instead of direct contact. In the latter, it'd be better to have a 3-gang (or more, depending on series setup) cell holder in parallel rather than in a straight line.

But I have no idea how to draw that up as I'm still trying to figure out the circuits design and what components do what. At least I know what Fets do and kinda how to use them :p
 
Nope. Referring to these: https://goo.gl/jcUjRD (eBay)
They're actually $1.50 each. I think when I said $5, I was thinking of a difference isolater someone else used for a bms.

Here's a video on it:
 
mike said:
These are interesting. If I run a bunch of these, can I tie all of the 0v outputs together to have a common ground on the output side?
http://www.mornsun-power.com/uploads/pdf/B_D-1W.pdf

Kinda defeats the purpose of having an isolater, mike ;)

It's actually the ground side that needs to be isolated. So you don't want to connect all your Neg after the isolater together. Now, you could take 2 or more and connect their inputs/outputs in parallel, and you'd effectively take the output wattage and increase it. So, they are standard 1W, 2 would be 2Watt; or, 200mA to 400mA. But, it'd probably start being cost/space prohibitive to do that. Might as well use the really small power adapters for charging usb devices. Costs would be about the same or cheaper for higher amp output.

Or, you 'might' be able to build your own. (Note, this is theory, I could be way off on this)
Input:
* 2 Mosfets - to change voltage to AC
* a coil transformer with 1 coil primary, 2 or 3 separate secondary coils
Output:
* 4 diodes / coil to create bridge rectifiers
* capacitor after the rectifying to smooth the voltages.

There may need to be more parts, but I'm not sure. And I'm not sure if all those parts would take up less space for the given mA required to charge those cells (for example, if going with the B0505S-1W, you'd need 5 to get 1000mA output for max of the TP4056; this would equate to 15 B0505S modules in total, lots of space)
 
Well, the fellow in the video did describe the shorting issue. I think its due to the -in and -out being directly connected, so if you put the TP4056s in series with a series battery, each successive series will add 3.7V to its corresponding board. Same as how the balancing cables work.

Since those isolators are only 0.2A, I'm afraid the won't work for me. I tried looking at Linear Tech.s website, but I'm having trouble navigating it. It seems to be all datasheets.

I also just saw a vid of a guy using the other method, separate "wall charger" supplies to keep the grounds isolated. So why does that work?
I wonder if multi-port USB chargers like thishave common grounds?
 
@Mike: That won't work either. What are you trying to do do with the arduino? Are A0-A2 directly connected to a cell? Or is there a charger board in between? Or something else all together?
Connecting the grounds together on the cell side of things is what is causing the issue with the TP4056 board during charging. As rebelrider said, it's because of the successive voltage of each cell. Because the charging Negative and the Power Neg are directly connected, once you go past 1 cell into the 2nd, you now have 8+ V, which blows out the 2nd and then 3rd TP4056.

However, I do wonder, if you were to put a diode, or a resistor between grounds, if it would have a different response. Those are areas I'm not sure about. Not sure about the direction of the diode either.
We think of ground as ground, always. The problem is the "ground" connected at cell1/cell2 is also the Positive, same goes for cell2/cell3.
 
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 getAC 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?
 
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 singlepower 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 AfrotechmodsThat 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.
 
Thanks, I missed that! I've removed my bad example above for the safety of future noobs like me who might read it. :)

Is that why FETs are used to reduce voltage? Because they work with DC?
 
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.
 
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.
 
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:
[img=800x602]https://s-media-cache-ak0.pinimg.com/originals/b7/4b/34/b74b34279b33eafdc4ed88d2dd195a0e.jpg[/img]
 
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.
 
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_uvbrod.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:


Descriptions:

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

Features:

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.
 
First off, to put youtube videos in, its:
Code:
Convert:http://youtu.be/i8_XV5Yn7_s[/video]
To:[MEDIA=youtube]i8_XV5Yn7_s[/MEDIA]
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 ;)

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 :) *please don't let someone pop my bubble :p *
 
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