Hi, I thought you had Enertia Basic, but it's actually Enertia Plus :-)
The procedure is the same except that the Enertia Plus does not have six 12V batteries,
but has two 44V battery modules.
In the picture you can see the removed bottom cover on my Brammo Enertia Plus and the bottom battery module with the Sevcon electronics attached. The main +/- contacts of the module are in the lower back of the case. There are also contacts for BMS.
If you get a charger suitable for lithium cells and 44V, you can try charging the modules separately. Can you measure the voltage of each module?
!But first, please disconnect the main contact inside the frame near the rear shock absorber!
If one of the battery modules cannot be charged using an external charger, the module will need to be disassembled and try to measure the voltage on each battery cell!
BTW: I also own the Enertia Plus, but so far I had no problem with the batteries. If it was necessary to disassemble the battery modules, a friend of mine from Italy has the experience with it.
BTW2: Do you have any original Givi side case holders for your Enertia?