Help choosing resistor for limiting current

Thread Starter

Astrotate

Joined Jul 6, 2020
3
I am making some power banks out of some spare 18650 cells I have laying around I am using a 5V Boost Step Up Power Supply Module.

Link: https://www.amazon.com/gp/product/B07D3SQYKJ/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1.

The only issue i face is that these chips will allow themselves to output a higher current than they can withstand without external cooling. I am looking to regulate the current to 500mah at 4v. Is using a simple resistor going to accomplish this?
Thanks for any help!
 

KeithWalker

Joined Jul 10, 2017
1,055
What load are you connecting to the output of this module? If the load requires more current than this module can supply then use a different one. If the load requires a current limiter, then add appropriate current limiting circuitry. We cannot recommend what to use because we do not know what your load is.
Regards,
Keith
 

crutschow

Joined Mar 14, 2008
25,126
You could add an external linear-type current limiter circuit but that will dissipate power, which will require a heat sink.
 
Last edited:

Thread Starter

Astrotate

Joined Jul 6, 2020
3
i only need 500 mah just using for general charging of random household electronics. in my tests it will just allow itself to get up to almost 2A which seems a bit too much for the chip onboard. if anyone has any suggestions for a cheap boost converter would work for this. also in the images below there is a pin marked R0 and has a zero ohm resistor. i do not read any continuity between it and b+ or B-. this leads me to believe that i could switch the resistor to something like an 8 ohm resistor. Although this may just result in the same heat loss thanks for all the advice everyone!
 

Attachments

Thread Starter

Astrotate

Joined Jul 6, 2020
3
I also dont know exactly how i should wire a boost converter to this circuit because there is only a single battery pin out for + & -. i want to regulate the current entering as well as exiting. so i would need a current regulator that works in either direction? if anyone knows a simple circuit that i could put together for this or better yet a chip that does it already that would be great too. also in the images below there is a pin marked R0 and has a zero ohm resistor.
 

BobTPH

Joined Jun 5, 2013
2,433
I think you are overthinking the problem. Tell us what you expect to connect to this that will require current limiting.

Hint: do not say a phone. They will only draw 500 mA max unless you do something to signal that they can draw more.

Bob
 

KeithWalker

Joined Jul 10, 2017
1,055
I don't undersand what you are using this for. You say it is to charge random household electronics. Battery driven electronics that use LiPo batteries have a built in charger circuit which regulates the voltage and current to the battery. All you need to charge them is a 5VDC supply without current limiting. Devices using built-in Ni-MH batteries also have built in charge controllers that limit the current but each has it's own specific input requirements.
The device you have is a 5VDC input single cell Li-Po charger with the charge current to the battery limited to 0.8 amps and voltage cutoff of 4.2 volts. It also contains a boost convertor which is powered by the same single cell and will supply 5VDC, 1 amp with short circuit protection,overload protection.
If you are going to charge other devices with this, what are you going to power it with and how are you going to connect it to the other devices? A simple 5V USB wall-wart would be a better choice.
This module is a step-up converter for building into a battery powered device to supply it with 5VDC from single Li-Po cell. It has a built in charger to recharge the cell.
Regards,
Keith
 
Last edited:

WBahn

Joined Mar 31, 2012
25,918
I am making some power banks out of some spare 18650 cells I have laying around I am using a 5V Boost Step Up Power Supply Module.

Link: https://www.amazon.com/gp/product/B07D3SQYKJ/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1.

The only issue i face is that these chips will allow themselves to output a higher current than they can withstand without external cooling. I am looking to regulate the current to 500mah at 4v. Is using a simple resistor going to accomplish this?
Thanks for any help!
What does it mean to "regulate the current to 500mah at 4V"? This is exactly the same as saying that you want to regulate the current to 3.6 coulombs at 4 V.

What, exactly, is it you are trying to do?
 
Top