Discharging station for Li-ion batteries

Discharging station for Li-Ion batteries

Li-Ion Battery Testing Process: The testing procedure involves several steps: measuring internal resistance, assessing voltage drop under load, and determining battery capacity. This process requires a fully charged battery, followed by a 1A load test after 24 hours. A battery with a capacity between 1500–4000mAh should not immediately drop below 4V under a 1A load; if it does, it is deemed unsuitable for further use and should be discarded. Passed the previous step batteries are discharged to 3V using an electronic load to measure their capacity. Measuring internal resistance also helps identify and eliminate defective batteries before undergoing charge/discharge cycles.
Safe Disposal of Rejected Batteries: Discarded batteries still contain residual energy and should not be disposed of while charged. Damage or short-circuiting of such batteries can lead to overheating and potential fire hazards. Additionally, the stored energy in these batteries can be repurposed for other uses.
Purpose of the Discharge Station:
- To capture and utilize the remaining energy from batteries.
- To fully discharge batteries, ensuring they are safe for further recycling.

The discharge station comprises two separate compartments with distinct connection terminals on opposite sides of the housing:

Energy Extraction Compartment: This section safely discharges batteries to extract usable energy. It features protection against reverse polarity connections using an ideal diode and monitors battery voltage via a voltmeter.
Deep Discharge Compartment: Designed for fully discharging batteries before recycling, this compartment uses a load of six resistors with an LED indicator to signify the discharge process.

The following key components are shown and numbered in the first photo above:

12mm metal rotary button - Used to activate the voltmeter.
BMS 1S 10A - Prevents deep discharge of batteries, especially when discharging functional batteries without risking damage
Module XL74610 - Acts as an ideal diode (up to 15A without a heatsink) to protect device components from reverse polarity connections. Traditional diodes, including Schottky diodes, are unsuitable due to their high voltage drop in low-voltage applications. As an alternative to the ideal diode you can use the protection circuit described here.
Voltmeter 2wires 0.28inch - Displays battery voltage levels and is activated by pressing the rotary button.
USB boost module TPS61088 (input 2.8-4.5V) - Supports fast charging protocols like QC2.0/3.0 (5V3A, 9V2A, 12V2A), FCP, AFC, and DCP up to 24W. Heatsinks are installed on the module to enhance cooling and efficiency.
3mm green LED - Indicates the process of a battery deep discharging.
100Ohm 0.25W resistor (Amazon)(AliExpress)- Protects the LED and limits its brightness. The resistor value can be adjusted to modify brightness levels
6 parallel connected 10W resistors with resistance 51Ohm - Combined to achieve a total resistance of 8.8Ω, facilitating deep discharge with a current of approximately 400mA.

The device is housed in a transparent plastic box, commonly used for office supplies.

Optionally, USB wattmeters like the HiDANCE HDC-085C can be used to monitor the charging power, voltage, and current of USB devices.