How do you calculate lithium vs lead-acid payback for a 20-cart fleet using your own numbers?

Direct answer: Build the comparison per cart, then multiply by 20. On the lead-acid side count battery sets over a fixed period, watering and cleaning labour, energy, and any downtime cost. On the lithium side count packs, any new chargers, installation parts and labour, and energy. Payback is the extra upfront cost divided by the yearly saving. We give the method only, because prices, use and labour rates vary too much for a general figure.

Step 1, define the period and use. Pick a period, for example the warranty period. Redway golf cart pages such as the 48V 100Ah and 48V 150Ah list “Warranty: 5 Years”. Count rounds per cart per year and convert to cycles; our post on estimating energy per round shows how to get kWh per round.

Step 2, lead-acid cost per cart for the period: (number of battery sets you would buy in the period × set price), using your own replacement history; plus watering and terminal-cleaning hours per year × labour rate × years; plus energy per year × tariff; plus disposal of old batteries; plus lost rentals or spare carts kept because of battery downtime, if real.

Step 3, lithium cost per cart for the period: pack price; charger cost if your chargers cannot be set to the pack’s profile (the 48V 100Ah lists 58.4V maximum charge, while the 48V 150Ah lists 54.75V, so the two need different settings); installation parts such as hold-downs, cables, and a DC-DC converter if the cart runs 12V accessories (see DC-DC converters); fitting labour; energy per year × tariff.

Step 4, check life assumptions. The pages list more than 6,000 cycles at 80% DOD. A cart that does, say, 300 cycles a year would use far fewer than that within five years (our arithmetic), so the period, not cycle life, is likely to bound the comparison; ask what happens after the warranty ends. Do not mix cycle numbers measured at different depths of discharge.

Step 5, compute: yearly saving = (lead-acid total − lithium total excluding upfront items) ÷ years; payback = (lithium upfront − lead-acid upfront in year one) ÷ yearly saving. Multiply by 20 carts and run a low and a high case. For the buying side, see questions before a fleet order.