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Hacking a TP4056 charger module
#1
I have a bunch of TP4056 modules in my mass charger. I have noticed they charge to about 4.22 volts, range is 4.20 to 4.25 volts. This is quite a bit higher than I would like. Is there any way of reducing the charge voltage to say 4.05 volts? It would be great to have one common reference voltage fed to all the TP4056 modules so they all charge to exactly the same voltage. Has any clever electronics person experimented with this?
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#2
It looks like TP4056 chip has fixed voltages built in & no options for changing, eg a resistor value.
You could put a schottky diode in series with the +B lead & get a drop of ~0.3V but it increases losses when charging.
Rad and Korishan like this post
Running off solar, DIY & electronics fan :-)
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#3
Nope, voltage is an issue. schottky diode is probably the easiest and cheapest way of doing it. Altho, I think the diode would keep the TP from properly monitoring the cell, as well. Afterall, diodes only allow voltage in direction. So wouldn't the TP not see the voltage of the cell and either 'not' charge at all (thinking there is no cell) or still overcharge?
Perhaps putting a diode in both directions?

I'm not sure on that part as I haven't messed with them to that point. Just thinking outloud and trying to get clarification before you solder up a bunch of TP's for naught Wink
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
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#4
In my tampering with the 4056's ive learned that even placing an ammeter in series with the output affects the charging cycle in a decent way, which is probably why they recommend doing in on the input (I was doing wrong for ages!)
Regarding diodes, i dont know about that kinda thing but my answer to everything is to MCU everything Tongue 

Maybe have a Nano with a couple of additional ADC devices like the MCP3008 and some IO expander devices like the MCP23S17 so you can measure the cell voltages during charge and disable the chargers as they hit a certain voltage. 
Thought the cells seem to settle down by about 0.15v after wards so maybe a limit of 4.20v to stop the cells continuing with constant voltage phase. May just give you the result you want. Its what i do anyway

How many TP4056 modules do you have in this mass charger?
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#5
Not a bad idea modding the charger and adding intelligence to it. It has 30 modules so would need at least 30 ADC input channels and 30 IO lines. I am in the process of building a 30 bay mass discharger, it could also do with some MCU.

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#6
(06-10-2018, 03:00 PM)Rad Wrote: Not a bad idea modding the charger and adding intelligence to it. It has 30 modules so would need at least 30 ADC input channels and 30 IO lines. I am in the process of building a 30 bay mass discharger, it could also do with some MCU.


Very nice Wink I love a tidy job
In that case you'd need x3 MCP3008's (each give 8 analog inputs via SPI), x2 MCP23S17's (each gives 16 I/O's via SPI)
And that'll leave x10 digital I/O pins spare and x2 analog inputs spare

There may be bigger expanders out there but these are the only ones I've used.
The serial log can be sooo handy. If you wanted to log charging current though you'd need another x4 MCP3008's on top of it all Tongue
You may have a lot of wiring ahead of you if you choose this path!
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#7
Unfortunately TP4056 doesn't have an external reference input and the internal is fix 1.22V
Just add a resistor in series with the battery. The voltage gonna drop and you can change it with the resistor value. For example: a 0R05 resistor gives you -0.05V
Cutting the battery before reach a certain voltage(<4.2) is not recommended, it's gonna miss the CV stage!

Best option: use a different charger IC which perfect for your needs.
Best option2: Check your TP modules and use the good ones. You can measure the Voc without battery, that's a good indication.

BTW I'm not surprised on the voltage swing what you experienced, a lot of TP clones out there.
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#8
Thanks for the suggestions, yes it would add a fair bit of wiring, if I used thin ribbon cable it could be quite neat though. I should have done the mods right in the beginning, I have now charged about 1900 cells out of 2600 so will soon start discharge testing soon.
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#9
Recently came across this article: https://hackaday.com/2018/06/09/arduino-...ltiplexer/

It's a good read, and the comments have a lot of good added information on which MUX's to use as well.

(06-10-2018, 03:49 PM)Rad Wrote: ...I have now charged about 1900 cells out of 2600 so will soon start discharge testing soon.

Well, this is just your beginning. Before long, you'll have over 5000 cells Wink
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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#10
(06-10-2018, 03:23 PM)FERCSA Wrote: Unfortunately TP4056 doesn't have an external reference input and the internal is fix 1.22V
Just add a resistor in series with the battery. The voltage gonna drop and you can change it with the resistor value. For example: a 0R05 resistor gives you -0.05V
Cutting the battery before reach a certain voltage(<4.2) is not recommended, it's gonna miss the CV stage!

Best option: use a different charger IC which perfect for your needs.
Best option2: Check your TP modules and use the good ones. You can measure the Voc without battery, that's a good indication.

BTW I'm not surprised on the voltage swing what you experienced, a lot of TP clones out there
The 'hidden' reference voltage is a great pity, I think your option 2 would be great. Just buy heaps of them and test and sort them!
Harvesting and cleaning and charging
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