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Photovoltaic Harvesting Team: Battery Charger The battery charger is responsible for regulating power to the lithium ion batteries. These batteries are a potential hazard when over charged or when charged too rapidly. The LTC4006 Standalone Li-Ion Battery Charger is capable of charging 2, 3, or 4 cell stacks of batteries safely and efficiently. Lithium ion batteries should be trickle charged when below 10% charge or above 90% and receive max current otherwise. What is unique about this battery charger is the ability to divert power around the charging circuitry to the load. This feature allows the energy from the photovoltaics to drive the load when needed and support larger currents. Equipment Needed: 1. DC power source 2. LCT demonstration board 3. Lithium ion battery stack Start Date: March 16, 2012 Finish Date: March 16, 2012 Engineer set-up experiment: Mike Grolling Assistant: Test Plan: Test # Component / System Tested Description Engineering Spec Pass/Fail Criteria 1 Lithium ion batteries Batteries energy storage capability 6 ~ 5 A-H 2 LCT4006 Proper charging of lithium ion batteries. N/A See Figure 1 Figure 1: Example Charging Curve for Lithium Ion Batteries Test Results: Test # Measured Result Pass/Fail? Comments 1 N/A N/A This requirement is an energy rating of the battery stack. 2 See Figures Pass In agreement with the charge curve for lithium ion batteries Figure 2: Charging Curve Figure 3: Switch Event from Trickle to Full Charge Rate Comments/Observations: The requirement for 5-Amp hours (spec6) will be met by the 4-cell battery stack. Testing was performed on a 2 cell stack. As shown in Figure 2 the control circuitry of the LTC4006 never allows the voltage on the battery to rise above the maximum allowable voltage which is 8.4 V for this battery stack.