Make your own LED Battery Level Indicator
Summary
TLDRIn this video, the creator constructs a lithium-ion battery pack enhanced with a Battery Management System (BMS) for safety. To visually monitor battery levels, they explore using an LM3914 IC, which drives LEDs based on voltage levels, providing a basic battery level indicator. However, finding the standard approach lacking in precision, they design a custom LED battery level indicator circuit. This new design uses six LEDs with adjustable trigger voltages for more accurate battery level representation, tailored to the specific discharge curve of their battery pack.
Takeaways
- 🔋 The video discusses creating a lithium-ion battery pack with a BMS (Battery Management System) to prevent overcurrent and easily charge the battery.
- 🔌 The creator is missing a battery level indicator and considers using a lipo battery voltage tester from eBay, but finds it inadequate for displaying energy percentage.
- 🚀 The LM3914 IC is introduced as a potential solution for driving LED indicators to show battery level, as it senses analog voltage levels and drives 10 LEDs accordingly.
- 🔍 The LM3914's datasheet is recommended for understanding the specific pin connections and settings for the IC to function properly.
- 🔗 The video explains the need to connect the IC's pins to either ground or supply voltage, and the use of a resistor to set the current for the LEDs.
- 📊 The LM3914 uses a resistor ladder to create different voltage potentials for the comparators, which light up LEDs based on the battery voltage.
- 🔄 The creator builds a circuit to demonstrate the IC's functionality, showing LEDs turning off sequentially as the battery voltage decreases.
- 🤔 The creator identifies a problem with the linear voltage decrease of the LM3914 not accurately representing the battery's discharge curve.
- 🛠️ A custom LED battery level indicator schematic is proposed, using six LEDs and manual adjustment of comparator trigger voltages via trimmers.
- 🔧 The custom circuit is assembled and fine-tuned with a boost converter module and trimmers to match the battery's discharge curve more accurately.
- 🔬 The importance of adjusting the trigger voltages based on the specific battery type's discharge curve is highlighted for accurate battery level indication.
Q & A
What is the primary purpose of creating a new lithium-ion battery pack in the video?
-The primary purpose is to build a battery pack for upcoming projects and to prevent over current events by attaching a suitable BMS (Battery Management System) circuit.
What is the missing feature in the battery pack that the video aims to address?
-The missing feature is a battery level indicator, which is essential for easily determining the remaining energy in the battery.
What device does the video suggest using to measure the voltage of each cell in the battery pack?
-The video suggests using a lipo battery voltage tester purchased from eBay to measure the voltage of each cell.
Why is the presenter not satisfied with the lipo battery voltage tester?
-The presenter is not satisfied because the tester does not easily convey the remaining energy in percentage form, which is crucial for understanding the battery's state.
What solution does the video propose for creating a more precise battery level indicator?
-The video proposes using an LED bar display, specifically by using the LM3914 IC, which can drive LED bars based on the battery voltage.
What is the function of the LM3914 IC mentioned in the video?
-The LM3914 is an LED driver circuit that senses analog voltage levels and drives 10 LEDs accordingly, providing a visual representation of the battery's energy level.
How does the LM3914 IC determine which LEDs to light up based on the battery voltage?
-The IC uses comparators that compare the battery voltage (sensed by the signal pin) with a set voltage window (set by the RHI and RLO pins), lighting up LEDs as the voltage decreases.
What is the issue with the linear voltage decrease provided by the LM3914 IC's resistor ladder?
-The linear voltage decrease does not accurately follow the actual discharge curve of the battery, leading to an inaccurate representation of the battery's energy level.
What modifications does the presenter make to the LM3914 IC's design to improve accuracy?
-The presenter creates a custom LED battery level indicator schematic that uses six LEDs, manual trigger voltage adjustment through trimmers, and sinking instead of sourcing current for better accuracy.
How does the presenter fine-tune the trigger voltages for the custom LED battery level indicator?
-The presenter sets the lowest capacity limit to 2.2 amp hours and the highest to 0 amp hours, calculates linear capacity steps, and adjusts the trimmers to output the required voltage to the comparators' inverting inputs.
What advice does the video give for using a different battery type with the custom LED battery level indicator?
-The video advises to look at the discharge curve of the different battery type to set the correct voltage values for accurate battery level indication.
Outlines
🔋 Building a Battery Pack with an LED Battery Level Indicator
The speaker is in the process of creating a lithium-ion battery pack for upcoming projects, discussing the need for a battery management system (BMS) to prevent overcurrent events. The video explores the limitations of a basic LiPo battery voltage tester from eBay, particularly its inability to display the remaining energy percentage in the batteries. The speaker introduces the LM3914 IC as a solution, which is designed to drive LED bar displays. They plan to create a more precise LED battery level indicator circuit, starting by assembling a test circuit based on the LM3914's datasheet.
🔧 Optimizing the LED Battery Level Indicator Circuit
The speaker tests the initial circuit with a constant voltage source and discusses its limitations, including the misconception that each LED represents 10% of battery energy. The linear voltage decrease caused by the LM3914's resistor ladder does not match the battery's actual discharge curve. The speaker proposes reducing the voltage window to focus on the linear section of the discharge curve and setting the last LED to indicate 12% energy. However, they decide to design a custom LED battery level indicator, using six LEDs, adjustable comparators, and a trimmer to manually set trigger voltage potentials. The project is completed after fine-tuning the circuit, demonstrating its effectiveness in accurately displaying battery levels.
Mindmap
Keywords
💡Lithium-ion battery pack
💡BMS (Battery Management System)
💡Battery level indicator
💡LIPO battery voltage tester
💡LM3914
💡IC (Integrated Circuit)
💡Constant current output
💡Resistor ladder
💡Comparator
💡Discharge curve
💡Custom LED battery level indicator
Highlights
Creating a new lithium-ion battery pack for upcoming projects.
Attaching a suitable BMS (Battery Management System) to prevent over current events and charge topics.
Using an eBay-purchased lipo battery voltage tester to measure each cell's voltage.
Desire for a battery level indicator beyond simple voltage readings.
Introduction of the LM3914 IC for driving LED battery level indicators.
LM3914's functionality to sense analog voltage levels and drive 10 LEDs accordingly.
Connecting LEDs to the LM3914 without current limiting resistors due to constant current outputs.
Setting the current for the LEDs with a 2 kilo ohm resistor.
Explanation of the LM3914's pin connections for voltage, mode, and bar graph activation.
Understanding the block diagram of the IC for comparator inputs and voltage potential connections.
Demonstration of the LM3914 circuit with a constant voltage source and geometric progression as signal inputs.
Observation that the linear voltage decrease does not accurately represent the battery's energy discharge curve.
Adjusting the voltage window to align with the linear section of the battery's discharge curve.
Designing a custom LED battery level indicator schematic with six LEDs and manual trigger voltage adjustment.
Building the custom circuit on perfboard with a boost converter module for trigger voltages.
Fine-tuning the custom circuit to match the battery's discharge curve for accurate level indication.
Testing the custom LED battery level indicator with a lab bench power supply.
Recommendation to review the battery's discharge curve for accurate voltage settings when using different battery types.
Encouragement to like, share, and subscribe for more creative and educational content.
Transcripts
as you can see here I'm currently
creating a new lithium-ion battery pack
for upcoming projects and by attaching a
suitable BMS circuits to the pack we
cannot only prevent over current events
but also charged topic easily the only
feature that is missing for me here is
battery level indicator for which we
could use this lipo battery voltage
tester that I got a for cheap from eBay
and while it certainly measures the
voltage of each cell correctly I'm not
thrilled about this play since you
cannot easily tell how much energy in
percentage is left in the batteries a
possible and awesome solution for that
would be an LED but display so in this
video let's talk about the classic LM
391 5c whose job is coincidentally to
drive led bothers place and furthermore
let's also create our own more precise
led battery level indicator circuits
let's get started
[Music]
this video is sponsored by jl CPC be one
factor bottom jlc PCB focuses on rapid
prototypes of one to six layer PCBs and
all of them are shipped directly from
the factories after being produced a
blow Dro Gerber files to test the fast
speed of prototype production and
delivery
according to the datasheet of the LM
three nine one four it is an ICU that
senses analog voltage levels and drives
10 LEDs accordingly which is basically
just what we needs since the voltage of
a battery can tell us how much energy it
got left
so I positioned a DI C on a breadboard
and had a closer look at its typical
application circuits given by the data
sheets the 10 LEDs need to get connected
with the cathodes to the pins 1 10 11 12
up to 18 and no they do not require a
current limiting resistor since the ICEA
features constant current outputs this
current can be set by connecting a
resistor between the ref out pin and
grounds I went with a 2 kilo ohm
resistor which gives us a current of
around six point two five milliamps per
LED next we have to connect v- to ground
v+ to the supply voltage
ruffridge us to ground and mode to the
supply voltage to activate the bar graph
modes and if you want to learn why
exactly I connected those pins to either
ground or the supply voltage then I
would highly recommend checking out the
datasheet since it is very well written
anyway what is left to connect are the
RL o seek and our H I pins which
determine to which voltage and voltage
range the LEDs will react to learn more
about it let's look at the block diagram
of the IC in a nutshell we cut n
comparators to whose inverting inputs is
the sake aka signal pin connected the
non-inverting inputs of the upper
comparator is connected to the RHI pin
while the following one's are all
connected to the previous non-inverting
inputs through 1 kilo ohm resistor and
the last resistor is connected to the RL
open now the signal pin usually connects
to the changing analog voltage so the
battery voltage while the RHI and our
elope
are connected to the voltage potential
window we want to cover for example if
we have a look at the discharge curve of
the utilized inr 18 650 - 25 our
lithium-ion batteries then we can see
that our voltage range starts at four
point one volts and goes down to around
two point nine volts multiply that by
four since I got a 4s 4p battery pack
and we got a voltage window of sixteen
point four to 11 point 6 volts so we
connect a 16 point formal potential to
our hie and an 11 point 6 volt potential
to our ello due to the resistor ladder
which acts like a voltage divider we now
got 10 different voltage potentials at
the comparator inputs and since we know
that if the inverting input has a higher
voltage than a non-inverting inputs the
outputs will be pulled down to grounds
meaning the LED on the output will light
up it all starts to make sense as the
battery voltage decreases it reaches the
10 different resistor ladder voltage
potentials turns the output higher and
thus turns the LED off for demonstration
purposes I built up the described
circuits with a constant voltage source
and upon a geometer as a signal inputs
and as you can see when the battery
voltage drops the LEDs turn off one
after the other
awesome you might think I will use that
for my new battery pack well if you want
a crude battery level indicator then go
for it but for me there's still a
problem since we got 10 LEDs you would
think that each one represents 10% of
energy in the battery pack but that is
not true
due to the resistor ladder of the ICEA
with only 1 kilo ohm resistors we get a
linear voltage decrease but if we would
mark those points in the discharge curve
of the battery then we can see here that
it does not follow the actual line very
well one solution for that is to
decrease the voltage window so that we
look at the mostly linear section of the
discharge curve
and while we edit we should also set the
last LED to 12% energy which the
capacity of 2.2 amp hours represents but
for me even those changes are not enough
so I came up with my own LED battery
level indicator schematic it basically
works the same way as the LM 391 for
whippits comparators but I only use six
LEDs no constant current methods source
current instead of sinking it and can
set the trigger voltage potential of
each comparator stage manually through a
trimmer and after I did a small
proof-of-concept test on the breadboard
I went ahead and sold out all the
required components to piece of perf
wards and connected them to one another
according to the schematic to create the
constant 20 volts for the power and the
trigger voltages
I also utilized a small boost converter
module which I directly sold outs to the
per port and after fine-tuning that it
was time to adjust the trigger voltages
for that I set my lowest capacity limits
to 2.2 amp hours and the highest one to
obviously zero and hours then I
calculated for linear capacity steps
between those two values and marked them
in the discharge curve according to the
point of intersection I took the reading
for the different voltage levels and
simply multiplied them by 4 to get the
right trigger voltage for the six
different binary states afterwards I
simply tuned the trimmers to outputs the
required voltage to the comparators
inverting inputs and just like that this
project was complete and as you can see
by doing a test with my lab bench power
supply it seems like everything works
like anticipators of course if we use a
different battery type you should also
have a look at the discharge curve to
set the correct voltage values in order
to get a pretty accurate battery level
indicator and with that being said I
hope you enjoyed this video and learned
something new along the way if so don't
forget
like share and subscribe stay creative
and I will see you next time
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