The drive battery holds a high voltage, something like 180volts.
But it should then consist of 180/1.5=120 1.5 v cells, right? So, is it possible to connect to only 8 out of those 120 cells to get exactly 12 volts?
They don't use Ever Ready HP7s.
NiCd and NiMH are 1.2V, but it's not those either.
The HV battery uses Lithium Ion cells which are not 1.5V, but usually 3.6 or 3.7V.
Many portable booster batteries are indeed four Lithium Ion cells wired in series to give about 14.4-14.8V output.