ESE 435 Lab 5: Batteries (2 Weeks) I. Outside preparation for lab Prior to coming to lab: 1) review the provided LabVIEW VI (for measuring current dependence of Thevenin-equivalent resistance of a battery) and the PowerSonic Battery Technical Manual and 2) study the Characterize Battery and Discharge Battery and Log Energy Vis and be ready to describe their operation and features. Perform a “back of the envelope” calculation to reconcile the liters/Ahr and kg/Ahr values for a lead acid battery. II. Lab Exercises Objectives: Measurement of battery characteristics (internal resistance, temperature dependence, discharging and charging behavior) using custom LabVIEW VIs and an Elvis II circuit based on an electronically controllable (MOSFET) load. Note: there is no simulation for this experiment. If you have suggestions for simulation, please inform your instructor. Concepts: - Basic battery chemistry - Thevenin (quasi-global) equivalent: VT and rT(i) - Temperature dependence - Discharge characteristics (battery voltage vs. discharge time) - Discharge characteristics vs. drain current - Capacity (Ah) and C rate - Charging methods - Efficiency (energy in/energy out) Equipment: - One frozen 6 volt PS-610 lead/acid battery (fully charged) - One room temp 6 volt PS-610 lead/acid battery (fully charged) - One temperature probe and handheld DMM - One IRF640 power NFET Provided VIs: - set battery drain current.vi (set target drain current controlled via MOSFET gate voltage) - Characterize Battery.vi (measures and plots V-I curve for equivalent resistance) - Discharge Battery.vi (controls discharge at fixed load current and measures and plots battery voltage) Measurement setup: - Circuit (very similar to photovoltaic load measurement circuit) will be provided on blackboard.Before starting this week’s procedures, demonstrate your understanding and modification (below) of the relevant measurement program(s) to the instructor. Caution: - During all steps, be prepared to turn off the Elvis board if measurements are far from expected values (or if you smell something overheating). - Terminate testing if battery voltage drops below 4.5V (the provided VIs are programmed to shut off automatically at this voltage). - Note: you may need to adjust step sizes for discharge current and MOSFET gate voltage in the VIs. Please consult with the instructor regarding changes before acquiring measurements. Modify provided Vi(s): - For step 7, you will design a VI and associated circuit for charging the battery and recording the charging characteristics. Procedure: 1. Find the current-dependent Thevenin equivalent resistance, rT(i), for the +5V supply of the Elvis board over the range 0.0 to 0.5 Amps. 2. Find rT(i) (over the range of 0.0 to 1.0 Amps in 0.1 A steps) for the cold battery while monitoring battery temperature with the temperature probe, then set it aside to warm for 90 minutes. 3. Find rT(i) (over the range of 0.0 to 1.0 Amps in 0.1 A steps) for the room-temperature battery while monitoring battery temperature with the temperature probe. 4. Using the battery voltage discharge VI, discharge the room-temperature battery at 1.0 Amps and measure the voltage versus discharging time. Stop discharging when the battery voltage reaches the manufacturer specified limit (4.5V for PS-610 6V 1.1Ah). 5. Find rT(i) (over the range of 0.0 to 1.0 Amps in 0.1 A steps) for the fully discharged battery. 6. When the formerly cold battery has reached room temperature (or 90 minutes) repeat the measurement of its rT(i). Review the manufacturer specifications for charging these batteries, and design a charging circuit and LabVIEW VI. Have the instructor check your design before proceeding with the next experiments. 7. NOTE: The following steps will probably happen in the lab next week. Mark your discharged battery and save your measurements. a. We will add another discharge cycle for this battery just prior to recharging fully (next week). b. Charge the fully discharged battery with your design (per the manufacturer specifications, charge with a constant current of 300 mA until the battery voltage reaches 7.25 V, then continue at that constant voltage until current drops to 10 mA). Record the current and voltage you are monitoring. Also next week: - Charge controller and charge/discharge characteristics for NiMHIII. Report Special Section: Include a short report on one of the emerging battery technologies (examples are liquid metal, Prieto, super capacitors, etc.). Describe the technology and why it is novel. Also describe the technical challenges that must be overcome for it to be a commercially viable product. In general, follow the lab report guidelines distributed previously. For this lab, additional details are included below. Data: Include representative waveforms and measurements to document expected (and unexpected) results. Include schematics used for data acquisition. Analysis: Using your measurements of v(i), estimate the Thevenin-equivalent resistance rT(i) for the power supply, the cold and room temperature batteries, and the battery before and after discharge. Comment on these results. Plot your measured discharge characteristics for the room temperature battery and include the relevant plot from the manufacturer (with appropriate citation). Calculate and plot the energy delivered by the battery as a function of time. Compare your measured results to those of the manufacturer, and comment on any discrepancies. Plot the measured charging characteristics for the discharged battery, and calculate and plot the energy supplied to the battery as a function of time. Comment on the performance of your charging design. How did it perform compared to expectations (via the manufacturer)? Estimate the charging efficiency (energy in/energy out) from your results. How would you estimate the efficiency versus charging time from your measurements? Conclusions: Consider the implications of your results for utilization of batteries and design of charging controllers. As with previous experiments, comment on how we might improve the lab in any aspect you like, i.e., data taking, scope of circuit, equipment issues, etc. Also, please comment on aspects of the lab you enjoyed (so that we know what portions to keep and/or