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TP4056 tolerances and capacity testing results
#1
I saw discussion elsewhere about tolerances with TP4056 chargers meaning that 1 charger could charge to a higher voltage than another.
I was wondering what theoretical difference this could mean for results when capacity testing?
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#2
TP4056 units have a 1% variance. Which means it has a range of +/- 0.042V, or 4.242 - 4.158V. Pretty large range, imho. However, you can get a batch of the boards, then test each one with the same cell (this is pretty critical to the calcs). You only need to slightly discharge the cell between tests, say to around 4.0V (the TP unit may not trigger to charge at 4.10V).

The other option is to go with a slightly more expensive, but far more accurate charger, the TP5100.
Not only is this a more accurate charger, it has a wider range of input (4V - 15VDC), and there are far fewer fakes out there than the TP4056 (fake ones have >1% variance, can get extremely hot during charging, charge >500mA regardless of the resistor used).
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#3
That does sound like a fairly wide range, which is why I am considering how to minimise this varience during testing.
I am interested in knowing how big a problem this could be.
For a typical laptop cell with 2000mah capacity, what difference in capacity would the 4.242V- 4.158V range give?
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#4
Capacity is very small. Just look at any of the cells in the Cell Database, and look at the PDF docs. They'll show you the charts. Also look at the Thunderhearts video's or his test results. Very little capacity.

The problem is if the cells constantly being driven to 4.242V, it could shorten their life. Also, if setting the cells to rest, and 2 cells drop to 4.10 after a couple weeks, the cell that charged to 4.242V will have dropped further than the one that was at 4.158V. So which one is better? Without having checked and written the starting voltage on the cell, you wouldn't know for sure. You'd lump them together by default.

However, if you do like I mentioned above and test the modules, then you can get a ball park figure as to what their quality is. Then put all the similar ending voltage units together in sets, or weed out the ones that are way out and only use the ones that are closer to .5% variance, or even .25%.
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#5
For the purpose of capacity testing, I really don’t think the final charge voltage at the very tip top makes much of any difference. Little actual change. Even doing a slight overcharge once probably isn’t the end of the world either… but consistency sure is nice for those of us that have OCD lol.

I have some spare cell holders that don’t really have a home… I didn’t know about the TP5100, maybe ill get a few and making a little charging board.

Do you have a link the the chips spec sheet? I am curious what the charge +/- tolerances are. The higher input voltage is nice too… but I am seeing various listings with ranges from 11 volts to 20 volts. I suspect there may be some things to watch out for with these as well.
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#6
The final voltage for the TP5100 depends on the input voltage. The higher the input voltage the higher the final voltage according to documents I have read.
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#7
(10-22-2019, 12:07 AM)Bubba Wrote: The final voltage for the TP5100 depends on the input voltage.  The higher the input voltage the higher the final voltage according to documents I have read.

Well, that would be wildly unacceptable for a charger IMO… I would hate for my input voltage to play a roll in final termination voltage.  

That means I need to keep my input voltage very consist to each charging board.
 
Many times I power off battery... I could feed my RC charger 12 volts or 50 volts, if I ask for 4.19 termination, I get 4.19
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#8
(10-22-2019, 12:07 AM)Bubba Wrote: The final voltage for the TP5100 depends on the input voltage. The higher the input voltage the higher the final voltage according to documents I have read.

Please provide where you got this info from. I just went over the datasheet and I didn't see anywhere where it mentions that. To me, that would basically make it useless as a battery charger.

It does mention that there is a range of charging from 4.145 - 4.252, similar to the TP4056. However, I think these would be far more accurate as they are partially reliant on an external inductor instead of everything being internal. Voltage input range is 5V - 18V according the the datasheet, with up to 2A charging. It is designed to charge 1s/2s (4.2V/8.4V), so it is a more robust chip.
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#9
I posted here, but am going to start a new topic for this idea.
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#10
1. The higher voltage an TP4056 would potentially give in regards of it spec will not kill your battery. If it does that cell was already screwed
2. You dont see any major capacity difference. The testers all people use here arent good enough anyways to measure it.


Instead of putting time into things like this spend the time and money on getting proper inverter. That would save ALOT more money over time in losses Wink
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