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TP4056: Is the series shorting problem fixable?
#1
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: 40ef6d319cb3f8ff824bebaf38338f86.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?
BlueSwordM likes this post
-Mike G
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#2
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 Tongue
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#3
Is this anything close to what you mean by an isolator? 
 https://smile.amazon.com/dp/B06XKSFGXX/_...WT4MN2UZBQ

If not, I suppose I could get a few of these wall chargers:
https://smile.amazon.com/dp/B01DBQ1U5S/_...WT4MN2UZBQ
These should keep the short from happening, right?

When I get time, I'll do some more searching on websites besides Amazon.
-Mike G
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#4
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:
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Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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#5
These isolated power supply modules are a working workaround, but the charging gonna be slow (200mA). Linear Tech. has some better modules but it's way pricier. The second thing with this solution is the efficiency.. way too low.
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#6
(08-21-2017, 01:22 PM)Korishan Wrote: 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.

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
Solar Setup: 9x 320w panels, PCM60X charge controller
Battery Setup: 14x 120 cell 18650 packs, 48v configuration

Recommended Items:
Opus BT-C3100, Cell Heat Shrink, 4-Cell Holders
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#7
(08-21-2017, 01:54 PM)mike Wrote: 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  Wink

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)
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Dollar Shave Club. Best Razor I've ever used
Certified 18650 Cell Reclamation Technician
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#8
It's hard to explain, here's a diagram of what I'm trying to do. You'll see the issue. The Arduino inputs all share a common ground which is not possible to connect while the cells are also connected in parallel. I was thinking this B0505S thing might solve that problem as depicted below.
[Image: b0505squestion.jpg]
Solar Setup: 9x 320w panels, PCM60X charge controller
Battery Setup: 14x 120 cell 18650 packs, 48v configuration

Recommended Items:
Opus BT-C3100, Cell Heat Shrink, 4-Cell Holders
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#9
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 this have common grounds?
-Mike G
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#10
@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.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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