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Electronic Load

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Electronic Balance Signal Line

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Figure 1 Schematic illustration of experiments of the phosphoric acid calculated from changes in the weight of stack after the power source has been started and operated with a 100% load for about one hour. Weight changes were plotted as the difference from the weight when the power source was first started up, or 0. From these weight changes, it was found that water was being stored inside the stack until the stack's temperature reached 85 °C . Between 85 °C and 95 °C , the rate of water absorption and removal was equal, and when the temperature exceeded 95 °C , the removal rate exceeded the absorption rate. The initial phosphoric acid concentration was 90% and reached its lowest of approximately 80% 13 minutes after the power source was started up. At the same time, phosphoric acid's volume reached its highest level of approxmately 0.8cm 3 /g, a 20% increase over the initial volume. It was found that 50 minutes after power source was started up, the weight was equal to the initial value, and all the water that had been accumlated in the stack had been removed outside the stack. Using these start up and operation patterns, the average cell voltage fell at a rate of approxmately 0. lmV/cycle-cell (more than 700 cycles), yielding a favorable result. When considering applications as a potable power source however, it may be used in a variety of ways, and with varying frequency. Therefore, stack durability and reliability must be established to allow it to meet a variety of operation modes. As an example of these studies, Figure 3 indicates the weight changes when the load on this power source varies.

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