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.Cut the connectors sothat they will be flush with the inside of the PVC plate.Apply epoxy glue to the inside rim of the drilled holesin the plate, then apply epoxy to the outside rim of theBarb connectorsbarb connectors that will contact the PVC plate.Insertfor gas portsthe barb connectors into the holes and then applymore epoxy to the top and bottom edges where thebarbs contact with the PVC plate to assure a good seal.Clean off anyexcess epoxy, but also leave some to provide ample seals.Avoid gettingany epoxy inside the barb connector.This would block the gas flowthrough the connector.Lay the PVC plate aside and let it dry.Final assemblyPlace the electrode assembly onto the PVC plate and align.Take apiece of channel and position it, insert the screws in the holes with thescrew heads inside the channel.On the opposite side of the plate, placea washer around the screw, put a wing nut or other nut onto the screw andtwist it down to hold the channel and the plate together.Finish by apply-232ing the other two pieces of channel to the plate. Planar Fuel Cell StackTighten the wing nuts by hand, anddo not let the plate bend from overtightening.The plate should bestraight across without the slightestinduced curves.Keep the take off tabs clear of thescrews as you insert the screws.Inthis design, one of the take off tabscomes very close to one of thescrews, so it is important to move itaround the screw if necessary and besure that the tab is coated with aninsulated material such as silicone,liquid electrical tape or rubber dipCompleted fuel cell, with the back sidecompound as mentioned earlier toof the oxygen plate visibleprevent contact between the ribbonand the screw or channel.For more rigidity you may want to insert stiffmetal strips under the channel at several points to insure more even com-pression.If you do this, make sure you do not cover the air slots on the oxy-gen side with the metal strips.233 Planar Fuel Cell StackApply a coat of silicone to theedges of the electrode assembly.Completely cover the edges andwhere they meet the end plate toensure a gas tight seal.Then,smooth the edges with your finger ora razor blade to make a nice clean,even looking finish.Set the fuel cellaside to let the silicone dry.Prepare the stack for testingInspect the fuel cell stack to seethat everything is in order and theCompleted fuel cell showing thepressure screws are tightened.If youhydrogen inlet and outlethave doubts about the silicone cover-age on the edges, apply more toensure a tight sea, then let it dry for 24 hours before testing.You can attach a small piece of hose to the gas exit port barb connec-tor and connect a valve to control the amount of gas that exits the cell.This exit port gas regulation can help to fine tune and tweak the cell out-234put.You should be able to "dead end," that is, go from a completely closed Planar Fuel Cell Stackport and open the valve in increments for more exit volume.Please notethat you should not dead end the cell if there is no storage container withpressure relief as outlined in this book, or some such other exit for thegas.The GPS system has a check valve in the design which prevents thegas from flowing backwards in the system.This can cause excessive pres-sure build up in the fuel cell stack which can cause gas leakage, or rup-ture the membranes which will destroy the stack.Purging the stackTo purge the stack of air before introducing hydrogen you can use bot-tled gas, or purchase a good size helium balloon.When the balloon isfilled, have it left tied loosely so that you can open it easily.Put the noz-zle of the balloon on the exit port of the fuel cell and let the gas expel intothe fuel cell and out the entry port.At the same time, have the regulatorturned on to provide hydrogen and insert the hydrogen hose onto theintake of the fuel cell.Remove the balloon and the stackis purged.We have not used inert gas purging, since our system is experimentaland set up for short runs.For a permanent system, if there is a need topurge the stacks, inert gas purging and a built in purging system should235be considered. Planar Fuel Cell StackTesting the fuel cell stackTo test the fuel cell, your hydrogen production system needs to be setup and running, or you need another source of hydrogen available.First, connect the gas supply line from the regulator to the fuel cell entryport barb connector.As a general practice, always have some sort offlashback arrestor between the regulator and the fuel cell stack.This canbe a small flashback bubbler that you can construct and install, or you canuse a commercial flash arrestor.Use a multimeter or voltmeter to do an open circuit voltage test.Connect the leads from the meter to the positive and negative take off ter-minal tabs on the fuel cell.If you are using the GPS system design in this book, open the regulatorthat is connected to the electrolyzer/storage system to allow hydrogen gasto flow to the fuel cell.If there is a gas exit valve on the fuel cell, be sureto open it for full gas exit.Then, you can diminish the gas flow in incre-ments if you wish during testing.Allow the gas to flow to the fuel cell for a minute or two, and then takethe reading from your voltmeter.Readings should be from 15V through9.6V.After a while the voltage will drop and plateau at various points.You236 Planar Fuel Cell Stackcan expect the cells to settle out and maintain a constant voltage ofaround 7.5 to 10.8 volts
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