Also, isn't LHCS generally likely to have more battery capacity because they're expected to be left without a power supply for certain amounts of time (e.g. when swapping locos, doing turnarounds), whereas D and EMUs can almost always supply themselves with the exception of faults, and EMUs being taken off the wires (not a routine operation). To be fair, I have no idea how the Mk4 was designed, I presume they knew how they'd be operated, but for older LHCS certainly battery capacity was more important, hence would be more extensive than on modern multiple units.