This is my first post having recently discovered this brilliant forum and I am hoping to learn from the impressive knowledge of this community.
I am soon to replace a bad HV battery module on my Panamera S E Hybrid PHEV but need some help to understand how best to charge/discharge and balance it to match the existing modules before installation. I just need to do this as a one off - since the on-board OEM BMS will take care of it thereafter. As an FYI the overall pack consists of 8 modules and 104 cells, each module being 13S1P.
With PPE at the ready I haven't yet stripped the HV pack down yet to get the specific module part numbers but anticipate they will be one of either 9A7915591A, B or C part numbers, depending on which module is faulty (isolation issue).
The workshop manual refers to balancing the replacement module using a VAS6910 balance/charger but at £15k that's not an option of course
Looking at the Porsche workshop manual and VAS6910 instructions it looks like the module will have a CAN connector with no direct taps to the cell terminals inside, which I think rules out using an external BMS like a low cost capacitive etc. Am I right in thinking this is similar to the VW modules, which use some kind of internal BMS (called a CMC?) which links to the main BMS over CAN. Is that right? How does the internal module BMS (CMC?) do it’s active balancing assuming the Porsche modules might work similar to VW modules? If I just apply a charge to the main +/- terminals will it auto balance between cells? Will the module need to also be powered up for this to happen? Or does no internal cell balancing take place without the use of appropriate CAN messages to make it happen?
Alternatively if we assume the modules will be fairly discharged at the point of doing the work, say to 3.4/3.5 volts per cell, then is cell balancing even something I need to worry about with a replacement module ? i.e. could I just apply charge to +/- and stop when overall module voltage is at say 45V (assuming that is same as other modules) then forget about cell balancing, install the module and let the OEM BMS sort any cell imbalances out itself.
Thanks in advance for any assistance.
