In a video published on 8 October, Off-Grid Garage's Andy fully charged his whole 48V bank for the first time since connecting the new "PowerWall" side. It now holds about 137kWh in seven batteries. The original battery shelf (three packs, 864Ah) sits right next to the chargers' busbar. The PowerWall batteries are further away, connected through four 95mm² cables, a breaker and a second SmartShunt. They are an MB56-cell pack, a CL530 pack and two packs of about 310Ah, around 1,778Ah by our sum. Andy describes them as double the shelf's capacity.
In bulk, at about 54V, each side took about 50A. The two shunts read about 100mV apart, which Andy puts down to "all the cabling and connection points". Twice the capacity got the same current. By our arithmetic, that means the shelf was charging at roughly twice the C-rate of the PowerWall.
Then the shelf neared full. At 54.66V the split was 42A to the shelf and 100A to the PowerWall. Near 55.2V it was 5A against 140A. Inside the PowerWall, the MB56 pack took almost 70A while a 314Ah pack took 5–7A. One shelf battery took 1.9A while another battery in parallel took 70A.
Andy raised absorption from one hour to over three to let the packs settle. The CL530 pack, which carries one MB56 cell in place of a cell damaged in transport, peaked near 80mV of cell spread on a 2A balancer. A V19 JK BMS reported 78% state of charge at 55.4V while accepting 1.2A. His view is that the imbalance mostly shows when batteries are first added. He argues that ten short absorptions do the same job as one long one. With 70A flowing, the connectors measured about 32°C.
The bank worked. But on the charge side it behaves like its nameplate only at the top. For most of the day, the nearest batteries do more of the work. The Background explains why.