I have an ESS system consisting of two Pylontech US5000 battery modules and a Victron Multiplus-II 48/5000/70-50. It's all single phase and based in the UK. Initially I used a pair of basic 150A bus bars but have recently upgraded my wiring in anticipation of adding two 250/60 MPPTs and a 6.8kWp solar array.
Since my US5000 battery modules can in theory discharge at 100A continuous (80A recommended) each, and since I expect to add a third battery at some point, I decided to run separate Pylontech battery cables for each module rather than daisy chaining them.
So I have my batteries feeding into a Lynx Power In module, modified to take fuses, via a 125A mega fuse each. I then have the Multiplus-II feeding from the same Lynx Power In via a 200A mega fuse and a 275A Victron DC isolator. This is on 70mm2 fine strand cable as recommended. My MPPTs will connect to the Power In via 35mm2 fine strand wire and 80A, 70V mega fuses. At this point I will be adding a second Lynx Power In as I need the extra connections.
My question is whether I should have DC isolators on each incoming battery cable or whether it's fine to rely on the Pylontech modules to power down when commanded via the red button and rocker switches, plus removal of the positive amphenol connectors for final isolation? I would prefer not to cut the manufacturer fitted M8 lugs off the Pylontech cables and add M10 ones to work with the DC isolators and I don't feel that being able to isolate the battery modules individually is ideal and might cause problems in itself.
Another option would be to install the second Lynx Power In module and place an isolator between the two Lynx modules. But that would require the 8mm holes in the bus bar to be drilled out to 10mm to accommodate the isolator and even then, the isolator bolts are not long enough to accommodate the spring washer and nut. They are long enough to accommodate the nut alone but then I'd have to use thread lock or locking wire which isn't great. Or maybe use a different isolator. Or I'd have to use little short pigtail cables which adds resistance, complexity and points of failure.
So, my question again is, is it ok to run the standard 2m Pylontech cables in a ventilated conduit from the batteries to the Lynx Power In and simply have the inverter with a 275A DC isolator and each MPPT will have a solar PV DC isolator. Then when I want to power down the whole system I would isolate everything in sequence before commanding the primary battery to shut the whole battery array down before toggling off the rocker switches and finally removing the positive leads for guaranteed isolation. Before that last step I would observe the Cerbo GX and MPPTs were powered off to ensure no load was present. This would be a much more elegant solution with fewer DC connections but I want a sanity check on the safety and compliance aspects please.