Wire-up math for battery banks: series multiplies voltage; parallel strings multiply amp-hours. Shows watt-hours and optional usable Wh at a depth-of-discharge percent. Not a charge-time tool and not chemistry sales copy.
Reach for the battery series / parallel calculator when a planning number depends on measurements you already have on the boat or trailer. Enter cell / module voltage (v), cell / module capacity (ah), series count, and parallel strings.
Wire-up math for battery banks: series multiplies voltage; parallel strings multiply amp-hours.
Bank voltage equals module voltage times series count. Bank amp-hours equal module amp-hours times parallel strings. Watt-hours equal bank volts times bank amp-hours. Optional usable Wh applies DoD percent.
bank_V = cell_V × series_count
bank_Ah = cell_Ah × parallel_strings
Wh = bank_V × bank_Ah
usable_Wh = Wh × (DoD%/100)
Wiring math only — not charge time, BMS limits, or Peukert.
Start with the calculator’s default entries: Cell / module voltage (V) = 12; Cell / module capacity (Ah) = 100; Series count = 2; Parallel strings = 2; Usable DoD % (optional) = 50.
With those entries the calculator returns:
24.0 V · 200 Ah
4800 Wh · usable 2400 Wh @ 50% DoD
bank_V = 12 × 2 = 24.00 V
bank_Ah = 100 × 2 = 200.00 Ah
Wh = 24.00 × 200.00 = 4800 Wh
usable_Wh = 4800 × 50% = 2400 Wh
Formula used: bank_V = cell_V × series_count bank_Ah = cell_Ah × parallel_strings Wh = bank_V × bank_Ah usable_Wh = Wh × (DoD%/100)
One input at a time. Raise Cell / module voltage (V) from 12 to 18 and leave everything else alone. The result becomes:
36.0 V · 200 Ah
7200 Wh · usable 3600 Wh @ 50% DoD
bank_V = 18 × 2 = 36.00 V
Wh = 36.00 × 200.00 = 7200 Wh
usable_Wh = 7200 × 50% = 3600 Wh
Assumptions: inputs for this battery series / parallel estimate match the hints (soundings, nameplate Ah, marked tank capacity, and so on).
Do not. This page assumes identical modules in a balanced series-parallel layout.
Use bank Ah and charger amps elsewhere.
Series count 2 → 24 V bank if each module is 12 V. Parallel strings keep Ah additive.