Hello Thomas Unfortunately I can't say, as I have connected the additional Delta 2 "battery" to an EcoFlow Delta 2 PowerStation. The Delta 2 housings are identical and can be stacked perfectly. I have 2x 1000Wh so that it is balanced. When I draw power, both batteries are discharged in parallel. For some applications it might be better if the additional battery is discharged first and then the main battery. Unfortunately, it currently only works in parallel. Perhaps a new SW will be released where this can be adjusted. But for the service life of the batteries it makes more sense to charge and discharge both in parallel. That's my opinion. But I'm not a battery specialist.