Here is a example of a dual voltage source being applied to capacitor and resistors in parallel which resemble a fuel cell, that are 2 sets in series (2 fuel cells in series) . Between the 2 sets in series acts as a common giving me a negative and positive voltage reading from two probe points.
http://www.falstad.com/circuit/under file of this java app click import and put the following code into the window
$ 1 5.0E-6 1.5642631884188172 50 5.0 50
t 272 112 304 112 0 -1 -0.6734268138587165 -0.6834763289542725 100.0
t 272 320 304 320 0 1 0.6734268138587147 0.6834763289542689 100.0
w 304 128 304 160 0
w 304 160 432 160 0
c 432 160 432 208 0 1.0E-6 11.989950484904444
c 432 208 432 256 0 1.0E-6 11.989950484904446
w 304 304 304 288 0
w 304 288 304 272 0
w 304 272 432 272 0
w 432 272 432 256 0
r 496 160 496 208 0 500.0
r 496 208 496 272 0 500.0
w 496 272 432 272 0
w 496 208 432 208 0
w 496 160 432 160 0
w 432 208 288 208 0
R 304 96 304 48 0 0 40.0 12.0 0.0 0.0 0.5
R 288 208 240 208 0 0 40.0 0.0 0.0 0.0 0.5
R 304 336 304 400 0 0 40.0 -12.0 0.0 0.0 0.5
r 272 112 208 112 0 440.0
r 272 320 208 320 0 440.0
R 208 320 144 320 0 2 500.0 6.0 -6.0 0.0 0.5
R 208 112 128 112 0 2 500.0 6.0 6.0 3.141592653589793 0.5
w 544 160 496 160 0
w 544 208 496 208 0
w 544 272 496 272 0
o 23 8 0 35 40.0 9.765625E-5 0 -1
o 25 8 0 291 40.0 9.765625E-5 0 -1