Charger TP4056 Resistor Type

[monsieurracine]

Hi,

I am new here and hope that you can answer a quick question about a little project of mine.

I would like to charge a 100ma/h 3,7 v Lipo with a TP4056.

The current can be adjusted by changing the resistor on the board. (datasheet says from 100mA to 130mA...I read, that you can also get lower mA though)

Lipo:
**broken link removed**

TP4056:
https://dlnmh9ip6v2uc.cloudfront.net/datasheets/Prototyping/TP4056.pdf


The Lipo needs something like 50-70mA I guess so I think a 27kO resistor should be fine, right?

Does the W of the resistor matter? I guess I would just use a normal one as SMD might be too complicated to solder.

Thanks everyone

 

[Les Jones]

The "W" (Watts) rating of a resistor is the maximum power it is capable of dissipating. The data sheet for the TP4056 does not give the internal circuit so it is not possible to work out the actual power dissipated in the resistor. As the supply to the circuit is 5 volts then the maximum power that would be dissipated in a 27K resistor would be if it had the full 5 volts across it. Even if this was the case there would be just under 1 mW dissipated. So any resistor you could buy would be able to dissipate this amount of power. I think 1/8 Watt (125 mW) are the smallest resistors I have seen.
I would check that the resistor does give the correct charging current as it is only an assumption that scaling the resistor value outside the given values is valid.

Les.

 

[monsieurracine]

Thanks a lot Les!

I will check the current before using it. Maybe less than 27k is enough from what I read here:

https://jimlaurwilliams.org/wordpress/?p=4731

I could ask the ExpTech guys what the perfect charging current is exactly.

But maybe better have a little less current. I'd rather like to be too careful with Lipos.

Anyway have a great day