Battery Bank Series/Parallel Configuration

Modules in SERIES add voltages to make the bus, modules in PARALLEL add amp-hours to make capacity. Series count = round(target bus V / module V); four 12.8 V LFP modules in series make a 51.2 V (nominal 48 V) bus, and two strings in parallel give 200 Ah. Usable energy = series x parallel x module V x module Ah x DoD / 1000: a 4S2P bank of 12.8 V / 100 Ah LFP at 80% DoD is 8.19 kWh usable. The actual bus lands on the module nominal (51.2 V), not the 48 V label; never mix chemistries, ages, or capacities on a bus. LFP ~12.8 V/80% DoD, flooded lead-acid ~12.0 V/50%. A configuration aid; the battery/BMS series-parallel limits, the inverter voltage window, and NEC 706 govern.

series_count = max(1, round(target_bus_v / module_v)); actual_bus_v = series_count x module_v; total_ah = parallel x module_ah; usable_kwh = series_count x parallel x module_v x module_ah x DoD / 1000.

Battery bank series/parallel configuration (series adds voltage, parallel adds capacity), by name; the battery/BMS series-parallel limits, the inverter voltage window, and NEC 706 govern.

The series/parallel relations are public electrical first-principles; the module voltage, capacity, target bus, string count, and depth of discharge are the design and product values.

Estimate. AHJ and licensed professional govern.

Field names used by the API: target_bus_v, module_v, module_ah, parallel_strings, depth_of_discharge, series_count, actual_bus_v, total_ah, usable_kwh

• Series voltage, parallel capacity series = round(target bus / module V), bus = series x module V; total Ah = parallel x module Ah; usable kWh = series x parallel x V x Ah x DoD / 1000battery-bank electrical first-principles
• Match and limits actual bus is a module-nominal multiple (must fit the inverter window); never mix chemistry/age/capacity; LFP ~12.8 V/80% DoD, flooded lead-acid ~12.0 V/50%; NEC 706 and the BMS governmanufacturer / NEC 706