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The deionized water/ethylene glycol coolant used in the Ford Focus Fuel Cell Vehicle (FCV) requires very low conductivity (< 5 μS/cm) to avoid current leakage and short circuiting, presenting a unique water chemistry issue. The coolant's initially low conductivity increases as: 1) ions are released from system materials through leaching, degradation and/or corrosion, and 2) organic acids are produced by ethylene glycol degradation. Estimating the leaching potential of these ions is necessary for design and operation of fuel cell vehicles. An on-board mixed-bed, ion exchange resin filter is used to maintain low conductivity by removing leached or produced ions. Various candidate materials were evaluated for leaching potential by exposing them to coolant at the design operating temperature for several months and periodically analyzing the coolant for ions.

An AMTEC cell optimization study investigated various cell design performance tradeoffs for an AMTEC cell operating in a 4-GPHS (General Purpose Heat Source) ARPS using 16 AMTEC cells per system. The design objective was to generate 141 watts at beginning-of-mission (BOM), 112 watts at 6-year end-of-mission (EOM), and 99 watts at 14-year EOM from the 4-GPHS/16-cell system at a system voltage of 28 volts (cell voltage 3.5 volts). Cell performance predictions on a system-level compared the effect of BASE tube number, BASE tube sizing, electrode performance parameters, thermal shield design, and condenser emissivity on cell-level and system- level performance. The selected reference cell design is 2 inches diameter, 4 inches length using electrodes characterized by a B=120 A-K1/2/m2-Pa and G=10, one cylindrical and 21 conical thermal radiation shields, and eight BASE tubes having a 0.40 inch diameter and 1.0 inch active length.