Need suggestion to use a controller.

Thread Starter


Joined Jun 14, 2018
I need to design a board that does the following:
1. Charging two 18650 type 3.7V batteries in series.
2. Shows the charging status with four LED indicators.
3. Fan speed controller (PWM).

I would be appreciated it if you can suggest a ready-made board that can do the above function, or suggests a controller IC that I can use in my circuit.
The size of the board should be small like ESP8266 Arduino.



Joined Nov 6, 2012
1) What do you intend to use for a Power-Supply ?

2) Does the Power-Supply need to be built-on-to the Board ?

3) Will the Batteries be mounted to the Board, or plugged-in ?

4) Will the Power-Supply be required to power the normal Battery-Load, and
charge the Batteries at the same time ?

5) How much Current does your Battery-Charger need to provide ?

6) Do you are about balancing the two Cells ?

7) How much Current does your Fan require ?

8) Do the Batteries power the Fan ?

9) Do the Batteries power the Fan with no External-Power applied ?

10) What controls the speed of the Fan ?

11) Why are 4-LED Charge Indicators required ?
Why not a single LED-flash-rate-indicator ?

12) Do the Batteries power the Charge-Indicator with no External-Power applied ?

13) How long are the Batteries expected to last ?

14) Do you care about Low-Battery-Voltage-Protection-Circuitry ?

15) Will you need a Sequenced-Shut-Down-Output
in the case of a Low-Battery-Shut-Down ?

16) Do You need any other Low-Battery warning outputs or devices ?

17) An ESP8266-Arduino is not particularly "small",
why are you using this Board as a size reference ?

18) Do You require a Micro-Controller to provide these functions for some reason,
or is a simple Analog-Control-System OK ?