Fuel Cell stack load configuration

Discussion in 'The Projects Forum' started by MdeJongh, Apr 10, 2016.

  1. MdeJongh

    Thread Starter New Member

    Apr 10, 2016
    Hi all!

    Currently I'm an automotive engineering student and I'm working on a project that involves an fuel cell.
    In order to test the fuel cell, when turning it on and thus generating voltage, we have to apply a load on the stack.
    My electronics knowlegde is relatively small so I was wondering if you guys could help me out with putting a load on the stack.

    I currently have:
    - A fuel cell with a + & - output.
    - A variable slide resistor.
    - Two multimeters.

    What I want to achieve is that one multimeter shows the stack voltages and the other multimeter shows the load (in A) being put on the stack.
    I want to be able to control the load with the variable slide resistor. I have started to draw out a circuit diagram and I was wondering if you guys could check this (see attachment) and confirm this is the right way to do it. And if not, how to do it better :).

    Thanks a bunch in advance!
    Kind regards,
    M. de Jongh.
  2. wayneh


    Sep 9, 2010
    It's unlikely that you want the variable resistor to function as the load. The battery is probably many times more powerful than the power rating of the resistor and will pop it like a fuse.

    You can use a transistor to control the power to a dummy load such as a lightbulb or a heater, and control the transistor with the variable resistor. To say much more, we'll need to know how much power you need to handle.
  3. wayneh


    Sep 9, 2010
    You'll also want a small ohms resistor in series with the load. You'll measure the voltage across it to calculate the current.

    Instead of a variable control, you might consider just a bank of power resistors. You'd then just manually attach the fuel cell to each one and make your measurements. Again, it comes down to how much power we're talking about.
  4. MdeJongh

    Thread Starter New Member

    Apr 10, 2016
    Hi, thanks for your reply!

    The fuel cell voltages is depended of the load put on the fuel cell. As an average it can generate 24V at an load of 4A but can regenerate 20V at 8A. In the future I want to generate 240W power max (24V at a load of 10A).
  5. KeepItSimpleStupid

    Distinguished Member

    Mar 4, 2014
    Can you not invest in an Electronic Load: e.g. http://www.bkprecision.com/products/dc-electronic-loads/8540-150-w-dc-electronic-load.html

    It has constant current (CC), Constant Voltage (CV) and Constant resistance (CR) modes.

    Here's https://www.circuitspecialists.com/array-dc-electronic-load-3715a.html a cheaper one with constant power as well.

    Pololu offers hall effect current sensors in a breakout form that may be more appropriate for measuring current: https://www.pololu.com/search/compare/118 They do require a power supply.

    The effective resistance is about 2 milli-ohms in some cases. The output ends up being isolated as well.

    Current measuring "shunts" have 4 terminals. Two of them pass the current and two smaller screws measure the voltage. The resistance is precise between the two smaller screws. Here http://www.rammeter.com/ram-meter-a...nt-shunt.php?gclid=CMn8urCxhMwCFVdahgodCSoKPA is an example.

    Your resistor method is going to get old after a while.
    Last edited: Apr 10, 2016
  6. BR-549

    AAC Fanatic!

    Sep 22, 2013
    "The fuel cell voltages is depended of the load put on the fuel cell."

    I have only read about fuel cells. I was under the impression that fuel cells were stacked like battery cells to achieve required voltage.

    May I ask, for a data sheet on the cell? I hadn't heard of this type of cell, is why I'm asking.