36V 50Ah or 100Ah lithium battery for light electric equipment: how do you decide?

Direct answer: Decide from three numbers: the equipment’s average current, its highest sustained current, and the hours it must run between charges. The 36V 50Ah stores 1.92 kWh and lists 50A continuous; the 36V 100Ah stores 3.84 kWh and lists 100A continuous. If the highest sustained current is above 50A, or the required runtime needs more than about 1.5 kWh with reserve, the 100Ah is the safer choice, provided its larger size and weight fit.

Page figures. 36V 50Ah: 38.4V, 1.92 kWh, 501 × 185 × 242 mm, 14 kg, 43.8V maximum charge, 30V cut-off, 50A continuous, 100A for 5 seconds, IP65. 36V 100Ah: 3.84 kWh, 640 × 245 × 220 mm, 26 kg, 100A continuous, peaks of 110A for 10 seconds, 280A for 5 seconds and 300A for 3 seconds, IP65. Both list charging from 0°C to 60°C.

Runtime. Hours ≈ usable Ah ÷ average current. With an assumed 15A average and 20% reserve, the 50Ah gives about 40 ÷ 15 ≈ 2.7 hours and the 100Ah about 5.3 hours. Measure your equipment’s current rather than using these illustrative numbers.

Current. The motor controller’s maximum continuous current must be below the battery’s continuous rating, and its start or stall current should fit within the peak rating and its duration. A battery that keeps tripping on starts is undersized for current even if it has energy left.

Size, weight and charger. The 100Ah is 12 kg heavier and longer. Both need a charger with a 43.8V maximum; charging faster needs a charger whose current suits the pack, within its listed limits. Ask Redway for the recommended charge current.

Golf cart versions. For golf carts, Redway also lists cart-specific 36V packs such as the 36V 50Ah golf cart pack (S3856, listed 56Ah, IP67, metal case); see choosing a 36V golf cart pack. For other 36V options, browse the 36V LiFePO4 range.

Peaks versus continuous. Our post on standard and high-current packs explains why the continuous rating, not the peak, should anchor the choice.

Peak ratings in practice. A short peak rating such as 100A for 5 seconds covers a motor start, not a long push up a slope. If the equipment regularly needs high current for longer, size by the continuous rating.