Fuel cell electrical properties tests

Test setup

Tests were performed using Parmova fuel cell experiments on 2016-11-18. Voltage and current were measured using measurement device revision 1. Various sanity checks were performed by simultaneously using a multimeter and cross-comparing its readings with readings from the measurement device. Acquired readings were processed with LibreOffice Calc for visual display as charts.

Objective of the tests was more detailed evaluation of fuel cell performance with the secondary objective of testing the measurement device. There was no detailed test plan, new experiments were performed on ad hoc basis depending on results of the preceding tests. This exploratory testing method lead to main focus going to investigating the capacitive nature of the fuel cells, together with estimates of sustainable power production from a single cell.

Load resistor used was rated 4.7 kΩ.

Measurement interval is different in different tests, and regrettably was not recorded. This means that results from different tests are not directly comparable.

Results summary

The relatively high voltage measurements acquired in earlier tests using only multimeter voltage measurement turned out to be inaccurate in the sense that the results depend heavily on the connected load. Even the modest test load of 4.7 kΩ was enough to cause voltage collapse to sub 100 mV region.

Calculations of power output suggest that the sustainable rate is in the 1 μW region. This very low value poses a problem for actually using the power for anything meaningful. Increasing the output should be given some priority.

Measurement device performed well regarding voltage output, calculated voltages being in line with multimeter readings. The maximum measurable voltage value is quite low, however. It should be increased to cover value of 700 mv at least. For current, the recorded values were very close to lower limit, making it difficult to draw conclusions. If such low values need to be recorded, the device should be adapted to measure them in more precise way.

Tests

First test

This was the first test, performed without yet realising the the capacitive effects are signigicant. The assumption was that voltage and power output will be constant during the measurment,

Measurement device was connected and measurement was started. It was observed that the voltage dropped significantly after adding a load. The conclusion was that the initial measurement above 600 mV was result of storing production of the fuel cell over extended period to capacitance in the fuel cell.

 

Discharge

To better measure the effect of draining the stored energy, measurement was started before connecting the fuel cell to the measurement device.

Completely straight voltage in the start is caused by actual voltage value (> 700 mV) going above the measurement device's maximum of 270 mV.

Recharge

Behavior of fuel cell recharging after use was measured by first connecting the cell to load for extended period of time, then starting measurement and disconnecting the load.

Recharge and dischage

Test started with fuel cell emptied by extended connection with the load. With measurement ongoing, load was first disconnect for a period of time, then reconnected. This way both recharge and discharge was captured in a single continuous recording.

Recharge and discharge with current

The same test setup as Recharge and dischange was used, with the exception that current measurement was also connected.

Results of current measurement seem quite unusable, since the values are so close to zero that the device cannot properly distinguish changes.

Raw data

Raw data from the experiments is available here.