Do some research on your Challenger MBT.
ALL, US military tactical vehicles are 24VDC. From a simple forklift through Hummers (Jeep on steroids), IFVs to MBTs. One standard, one voltage.
A Hummer has 2x12 VDC batteries. Larger trucks, like the HEMMET or 10T have 4, IFVs and Artillery guns have 4 as well, MBTs and tank recovery vehicles all have 6.
Basic elec says two 12VDC batteries wired in unison make 24VDC. Same theory, either 2x2s, or 3x3s, still make 24VDC. Difference being CCAs, even a wimpy hummer can slave off a tank with low but good batteries, so no need to abandon ship, either just fire up the APU, or call the 1st shirt over to slave you off.
It appears that the Challenegr dozer kit needs 28VDC, to operate it's electrical motor. Pretty much identical to our mieplough.
http://www.pearson-eng.com/dozerudk1.html