BATTERY PACK SIZING

Battery capacity is rated in Ah (current×time) or Wh (Ah×voltage). Pack voltage = cell voltage × series count; pack capacity = cell capacity × parallel count. Runtime under load follows Peukert's law: t = C·(C/I)^(k-1) where k is the Peukert exponent (1.0 for ideal, 1.1-1.3 for lead-acid, ~1.05 for lithium). State of charge (SOC) decreases linearly with discharged Ah for lithium, nonlinearly for lead-acid. Maximum continuous current (C-rate) limits power output and life.

• Wh = V · Ah
• t = C / I (ideal)
• t_actual = C · (C / I)^(k-1) (Peukert)
• SOC = (Ah_remaining / Ah_rated) · 100
• V_pack = V_cell · N_series; Ah_pack = Ah_cell · N_parallel

References & StandardsIEC 61960 (Li-ion), IEEE 485 (Pb-acid sizing), SAE J1715

Size battery banks for off-grid power, electric vehicles, UPS, mobile equipment. Compute required capacity from load profile and runtime target. Pick chemistry based on energy density (Li-ion ~250 Wh/kg, Pb-acid ~40 Wh/kg), cycle life (Li-ion 1000-5000 cycles, Pb-acid 200-500), and cost. For series strings, balance cells to prevent overcharge or deep discharge of weak cells. BMS is mandatory for Li-ion above small-format.