Today, we are going to take a look at this bad boy – an all-in-one 18650 battery module
that can be used to power different projects. What’s unique about this is that it has
everything you need to get started from battery protection, charging circuitry, battery level
indication and even a boost or step-up converter to produce both 5V and 3.3V output. We will
take a closer look at the module in this video and towards the end, we will also use it to
power a Raspberry Pi to see how long it will last.
Before we proceed, I would like to mention that while 18650 batteries are useful, they
can also be extremely dangerous. A small battery like this can deliver 20A of continuous current
with peaks of up to 95A. That is a lot of current and it can easily start a fire if
you are not careful. When not in use, please ensure that you store the batteries in a battery
case to prevent accidental short circuits. When using the batteries, make sure you insert
them with the correct polarity to prevent damaging the module. Also, be sure to also
use a suitable enclosure for the module if you decide to use one.
Going back to the module, it is available in different configurations and I’ve seen
options for one, two and even four cells. The cells appear to be in parallel which increases
the overall capacity and run time. This also means that you can buy the dual version and
use it with either one or two batteries, depending on your requirements. The listings also state
that the output current varies for the different variants and these are shown on screen. The
single battery module will set you back about 4 dollars while a genuine 18650 battery will
cost another 4-5 dollars which means that you can get a pretty decent battery backup
solution for less than 9 dollars.
These modules are mainly suitable for high power or high current applications such as
powering single board computers like the Raspberry Pi or for audio related applications like
amplifiers and so on.
The module itself appears to be of pretty standard quality. On the top side, you have
space for the battery, several 3.3V and 5V output pins along with a USB type A port which
can be used to charge USB devices. There is also an ON/OFF push button switch that is
used to control the outputs. The bottom side of the PCB contains all the circuitry needed
for all the operations. I’m not sure if you can view it in the camera but this particular
board has a bit of flux residue around the through hole connectors and the main controller
IC.
The board also contains two USB ports, one being a micro-USB port with the other being
a USB type C port. These are meant to be used to charge the battery and I would recommend
plugging in only one at a time. There is also a footprint for what looks to be a JST connector
and if you look closely then the terminals appear to be connected directly to the battery.
The copper pour around the positive terminal connects it to this pad here, while the other
one makes its way through this ground copper pour to the negative terminal. We can also
confirm this by using a multi-meter in the continuity or resistance mode. Please make
sure that the battery is removed before probing the board. Sure enough, we have a direct connection
to the terminals.
This is both a good and a bad thing. By having this connection, we can use the same module
with an external 3.7V Lithium battery. However, it can also pose as a safety hazard. Accidentally
shorting these pads will result in a very bad short that will most likely destroy whatever
is connected to it. Keep in mind that there is a direct connection to the battery here
without any protection circuitry.
Let’s now take a look at the individual chips themselves. We start with the USB charging
input that is either the micro USB connector or the USB type C connector. These two components
are P-Channel MOSFETs and these are being used to switch the input voltage and to also
stop the main IC output voltage from reaching the USB port. This will be clear when we look
at the schematic. The USB input is then fed into the main controller IC which is the TP5602
and this particular chip handles pretty much everything. It can charge a single Lithium
battery from an input as high as 7V. It also features overvoltage and short circuit protection.
The datasheet states that the programming current can be set from 0.1A to 3A, however,
there was no further information provided and neither could I locate a suitable resistor
in the schematic which could be used to set this. The listing does state that the charging
current is 0.5A however, as we will see later, it charges at a much higher rate than this.
The chip takes care of the different charging stages for a Lithium battery and it also displays
the battery status using 4 LEDs.
When the key or external switch is pressed, the main IC will enable the 5V output and
as you can see here, pressing it for 2.5 seconds will switch it into the standby mode. What’s
interesting to note is that it will automatically switch to the standby mode when light loads
of less than 30mA are connected to it. This is something to keep in mind, but if you are
using a module like this then you probably require much higher currents for operation
anyway.
The datasheet also contains an example schematic and this is what the module is based upon.
Notice that we need to use an external n-channel MOSFET to be able to disconnect the battery
and they recommend using the 8205A chip which is the next chip on the board. It simply contains
two, n-channel MOSFETs and this chip is commonly used in different battery modules, including
the TP4056 module.
Finally, we have the AMS1117 IC which is a low dropout, linear voltage regulator and
this particular one has a fixed output voltage of 3.3V. This is also the reason why the 3.3V
output is limited to 1A. If you want more current than this then you can add another
regulator directly from the 5V output.
Overall, I think it’s a pretty decent module given that you can use it and modify it to
suit you requirements. It’s now time to test the module and we will start by charging
the battery. Please make sure that you match the battery polarity by using the terminal
markings that are printed on the PCB. The first thing you will need to do is charge
it and I will be using a micro USB cable for this which is also plugged into a USB power
meter. Once plugged in, you will be able to view the LEDs blink and these represent the
charge state. The module appears to be charging at close to 2A which is higher than the standard
charge rate, however it is still lower than the max charge current that is recommended
for the battery that I am using. This is something to keep in mind when selecting a battery and
a power supply. The charge current does decrease towards the end of the charging cycle, so
there appears to be some sort of regulation as mentioned in the datasheet.
When charging, the output from the main IC is disabled, however, the USB voltage is directly
fed to the output and this means that both the 5V and 3.3V outputs are active. If you
look at the schematic, then you will see that the p-channel MOSFET highlighted here is responsible
for this. The input voltage is directly fed to the output. This is also the reason why
we have the two MOSFETs close to the USB ports. They have simply duplicated the circuitry
to pass the voltage from the appropriate port.
Once charged, you can press the switch to check the battery status as indicated by the
LEDs. This also enables the outputs. In order to switch OFF the outputs, you need to long
press the switch for 2.5 seconds.
For the final test, I decided to power a Raspberry Pi 3 with an HDMI display to see if it can
boot and also approximately how long it will last. For the software, I decided to stick
with the desktop version of the Raspberry Pi OS. The test was carried out soon after
flashing the image so this was the first boot and I did not configure any network access.
Once everything was connected, I switched ON the module and sure enough, it began booting
just fine. The entire setup ran for over 2 hours which is expected given that the current
draw was just around 1 amp.
All in all, I think this a decent module to consider for your next power hungry, battery
operated project. You need to ensure that you are careful when using it and adding a
separate case with vent holes just for the module is definitely recommended. That is
it for this video. Do consider subscribing to the channel if you would like to see more
of these videos. Thank you for watching and I will see you in the next one!