Thermistor Selection for TP4056: NTC Resistance Guide

[sophiecentaur]

And how do you know it will solve it?

 

[Trevo]

I don't know if it will that's why I have been asking you guys questions cause obviously you all are smarter than me.

 

[sophiecentaur]

OMG. So we're too smart to get involved.
Some people just won't be told.
In the end this is a safety issue and PF has rules about that.

 

[Trevo]

Am I missing something I never said you guys were too smart. I don't know how that's possible. I want to be safe also its just I want it to work and I'm asking how to do that.

 

[jim hardy]

well i learned a couple things from all this

first one was re-learning an old lesson - that being always start from a GOOD source of information, avoid imitations.

Secondly, apparently there is a 3.6 volt Li-Ion chemistry
and here's a charger IC made for it
http://cds.linear.com/docs/en/datasheet/4050f.pdf

which i think is better written than that one from Nanjing
because it gives detail about their "Temperature sensing " pin

The thermistor is connected from NTC (pin 2) to ground and is biased up by an internal 28.6k trimmed thin film resistor that connects to VCC through a P-channel MOSFET. This MOSFET also biases an internal resistor string to ground, from which voltage thresholds of approximately VCC/2 and VCC/8 are derived.
The NTC pin is compared to these thresholds by two comparators that have wired-OR outputs. The thresholds are selected such that an overtemperature condition will occur when the thermistor resistance is less than approximately 4.1k and undertemperature condition will occur
when the thermistor resistance is greater than approximately 28.5k. These correspond to thermistor temperatures of 50°C and 0°C for the specific type of thermistor listed above (many others will be close enough for most purposes).

I suspect the TP4056 is a knockoff of that Linear Tech device, and i avoid foreign knockoffs.
And i would NOT assume the Nanjing chip uses the same thermistor.
In other words, get your parts from a known reputable source.

OP needs to familiarize himself with Li-Ion charging
http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries

and make doggone sure he gets cells that are designed for recharging
and make doggone sure his contraption behaves, that is it applies correct voltage and current for his particular cells,
and make doggone sure it shuts down at expected temperatures.

Trevo - if you don't have the test equipment to do this, ie a good DMM and a good thermometer,
buy something ready made.

 

[Trevo]

Dmm?

 

[Drakkith]

Trevo, working with electronics and electricity is dangerous when you don't know what you're doing, even if it's just with a couple of batteries. Unfortunately it is beyond the scope of PF to teach you all about electronics and electrical safety. Thread locked.