How do you calculate the payback of lithium forklift batteries in a two-shift operation?

Direct answer: Payback is the extra upfront cost divided by the yearly saving, and both must come from your own numbers. List what you pay today per truck (batteries over their life, spare batteries, swap labour, watering and maintenance, charging-room costs, energy) and what lithium would cost (packs, chargers, installation, energy). Check that one lithium pack can cover two shifts with the charging breaks you actually have. We do not quote a payback figure because it depends entirely on these inputs.

Step 1, can one pack do two shifts? Measure energy used per shift, or estimate it from the current battery’s use. The 48V 280Ah page lists 14.33 kWh and the 48V 420Ah 21.5 kWh. Maximum continuous charge current is 150A and 200A respectively (at 10–45 °C), and the charger entry is 0.5C CC/CV. Our arithmetic: at 0.5C a large share of capacity can be returned in a break of one to two hours, if the charger and the electrical supply can deliver it. If not, you still need a second pack or longer breaks, and the case changes.

Step 2, today’s yearly cost per truck: (price of lead-acid batteries per truck, including spares) ÷ their service life in years in your operation; plus swap time per change × changes per year × labour rate; plus watering and maintenance hours × rate; plus charging-room costs you would avoid (only if they really go away); plus energy per year × tariff.

Step 3, lithium yearly cost per truck: (pack price + charger share + installation) ÷ expected life in years; plus energy per year × tariff; plus any monitoring or service fee. For the life input, use the page’s figure: “5 years or 3500 cycles (DOD 70% 0.25C)”. Convert your duty into cycles per year (energy used per day ÷ usable kWh × working days) and check which limit you reach first. If your discharge is deeper or charging faster than the test condition, treat the cycle figure as optimistic.

Step 4, payback = (lithium upfront cost − lead-acid upfront cost you would otherwise spend) ÷ (yearly lead-acid cost − yearly lithium cost). Run it at three energy prices and two life assumptions, so the finance team sees the range rather than one point.

What not to do: copy savings percentages from articles, compare cycle numbers measured under different conditions, or count charging-room savings while the lead-acid fleet still uses the room. For the charging side see planning charger power for a fleet and opportunity charging across shifts; for life terms see warranty questions.