Previously in Testing RC Bluetooth Car App and Motor Code I showed how I build and tested the RC car using Bluetooth. I also told that I used +12V power supply from the wall socket because my Lithium ion batteries were not charged and had issue with HC-05 Bluetooth. So here is more about the Lithium Ion batteries and chargers what I have plan to use with Arduino based RoboMaster.
For my Arduino Robomaster project I am using three 3.7V Lithium Ion battery ICR 18650 3800mAh in series for the power supply. I faced problems with power supply which not only effected the motor power but also the HC-05 Bluetooth module. When the power is not adequate from the power supply source from the batteries then the Bluetooth module will not receive adequate power then simply won't turn on. Using external power I was able to control the RC car as expected and there was not drop of the Bluetooth wireless link. I have read that when there is transmission of Bluetooth data there would be disconnection of power source to the Bluetooth module and that due to this after connection and first few data exchange the Bluetooth is disconnected from the mobile phone. So I felt necessary to have the lithium ion batteries fully charged first to have any wireless movement of the Arduino Robomaster.
One of the solution to using portable charger would be to use TP4056 - TC4056A Lithium Battery Charger and Protection Module.
The picture below shows the TC4056A Lithium Battery Charger Board Module.
The connection to the battery to be charged and the power supply is quite easy.
I wished to include this charger module so that when the Arduino Robomaster is in switched off, the batteries gets charged. However I found out that this is not good idea because the TP4056 or TC4056A module is designed to charge a single lithium cell, and their internal components (such as voltage references, feedback loops, and protection circuitry) are optimized for single-cell operation. So I think that if I connect cells in series, the voltage requirements and behavior change, and the protection circuitry might not function as intended.
Since I want to utilize the module I bought I will have to build a single battery charger. For this, I needed to find a 18650(18mm x 65.0mm) battery holder. With this I can charge the batteries one by one. For now I just want to get the Arduino Robomaster rolling. Later on I think I need to find a module which can charge three lithium batteries in series. One such module suitable for my robotic car is 3S 10A Li-ion Lithium Battery 18650 Charger PCB 11.1V BMS Protection Board which can charge the three Lithium Ion batteries.
References
# Quick HC-05 AT startup guide - Arduino RoboMaster Part 3
# Testing RC Bluetooth Car App and Motor Code -Arduino RoboMaster Part 4
# My First Arduino RC Car - Arduino RoboMaster part 6
# RC car Battery Charger- Arduino RoboMaster part 7