kΩ, where the system was still discharging before the voltage was recorded (Figure ). In contrast, discharge was usually incomplete during the standard polarization tests acquired at t=45 and 48 days (during overshoot), regardless of the Rext (e.g., Figure at t=48 days). In the latter case, except for the highest applied external resistors (Rext=300, 150, and 100 kΩ), the voltage versus time discharge profiles were abnormal and had not stabilized before switching back to OCV in advance of the next applied value of Rext. This information is shown in greater detail in the inset to Figures and for the discharge across 25 kΩ. Based on the voltage versus time discharge profiles, the local decrease in the power density curve at Rext=25 kΩ and the overshoot at Rext < 10 kΩ were likely artifacts related to insufficient hold times during standard polarization tests due to worsening electron transfer kinetics at the bioanode. This can be due to related changes in charge transfer components, including changes to the number and types of cytochrome proteins and conductive pili that may be optimal for those conditions, bioanode capacitance, electrical resistance of the bulk biofilm, or charge transfer resistance from the EAB to the electrode. Coincident with the proposed slower electron transfer kinetics at t=48 days was a reduction in OCV by approximately 50 mV compared to that at t=42 days (Figures and). Loss of OCV could be the result of a loss of cytochrome c charge carriers or a reduced EAB metabolism, thus supporting the hypothesis of an unhealthy EAB slowing electron kinetics. We also examined the polarization test (voltage versus time) discharge profiles after erosion of the outer EAB layers (t > 61 days). Data for t=61 days (Figure ) were representative of measurements at t=92 and 109 days (data not shown). The polarization curves did not show significant differences in slope in the ohmic region during phases ii or iii, indicating that the internal resistance was stable (Supplementary Materials, Section S5). The discharge curves returned to an exponential decay, resulting in a short-term stability being reached more often before switching back to OCV in the 1-to 2-hour cycle time under a standard polarization test.