Multiple LiPo Battery Charger

The University of Idaho Marching Band has been incorporating multimedia displays into their performances, including synchronized light emitting diodes powered by Lithium-Polymer battery packs. There is a need for a charging system capable of charging approximately 200 packs safely and efficiently within a one week time frame.

Background
A device which can charge multiple lithium polymer batteries is something that is unavailable in the current market.Charging the battery packs simultaneously can save a lot of time and effort. The circuitry to design the aforementioned device is one that can be achieved under a moderate budget. The prototype and the circuitry can be multiplied and extended as the number of batteries to be charged increases. Further improvement of the circuit can also reduce costs.

Problem Statement
The University of Idaho Marching Band has been incorporating multi-media displays into their performances, including synchronized light emitting diodes powered by Lithium-Polymer battery packs. There is a need for a charging system capable of charging approximately 200 packs safely and efficiently within a one week time frame.

Specifications

 * The Lithium-Ion Battery
 * Minimum Capacity: 800mAh
 * Configuration: 3S1P/11.1v/3cell
 * Constant Discharge: 20C
 * Peak Discharge(10sec): 30C
 * Pack Weight: 75g
 * Pack Size: 57x29x23mm
 * Charge Plug: JST-XH

Implementation/Testing
The ti bq241xx (bqSWITCHER) evaluation module delivers a suitable technique for evaluating a charging management solution for portable applications. The evaluation module used incorporates the ti bq24115 IC which fulfills the capacity of charging more than three battery cells in series safely and efficiently. The evaluation module for the bq24115 chip is default set to charge one battery cell, but by using the voltage output regulation formula, provided by the integrated circuit's datasheet, one can find the modifiable resistance across two nodes on the module and is able to configure up to three battery cells in series (~12v). By evaluating and observing the module, the constant current and constant voltage characteristics become apparent when testing. First the voltage begins to rise and current is constant. Once the voltage reaches maximum voltage the current decreases to prevent the battery from creating too much pressure inside possibly initiating a fire. Current drops to zero and voltage falls slightly due to charge termination. An occasional topping charge can be applied to top off the charge.

PCB Design
A PCB is being designed for the first prototype of the project. The PCB contains the tibq24115 switcher IC and it's evaluation module (EVM) circuit along with 10 Toshiba solid state relays (TLP3100) for 10 batteries. It also has microcontroller connecting junctions along with the EVM junctions for reading the values from the evaluation circuit. The PCB schematic and layout is shown below.

Team Information
Instructor-
 * Dr. Feng Li.

Team-
 * Ryler Adams
 * Abraham Martinez
 * Pankaj Dhyani

Agendas
Agendas

Minutes
Minutes