Make your own LED Battery Level Indicator

Summary

In 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.