If your stall needs lights, a card terminal, internet connection and a laptop, plan for the whole trading period, including setup and a late finish. Add the energy each item uses over time, then check which devices run together. A battery with enough watt-hours can still be unsuitable if its outlets, output rating or outdoor operating conditions do not fit the setup.
Make a trading-day energy budget
This example is a calculation, not a measurement or a product recommendation. Replace every assumed load and duration with your equipment's figures. A charger label may show its maximum draw rather than the average it uses while trading.
| Equipment | Assumed average | Time | Energy delivered |
|---|---|---|---|
| Stall lights | 20 W | 6 h | 120 Wh |
| Mobile router | 12 W | 8 h | 96 Wh |
| Laptop charging | 45 W | 3 h | 135 Wh |
| Card terminal charging | 10 W | 8 h | 80 Wh |
| Trading-day total | 431 Wh |
If trading runs two hours late with the lights, router and terminal still powered, add 84 Wh (42 W × 2 h). The example then needs 515 Wh delivered to the equipment. A nominal 515 Wh battery will not necessarily deliver that much: conversion losses, the station's own use and a reserve reduce what reaches the loads. For illustration, if 80% of nominal capacity reaches the equipment and you keep 15% of that usable amount in reserve, 515 ÷ (0.80 × 0.85) is about 758 Wh nominal. Those percentages are planning assumptions, not a measured efficiency or a promise for any station. Change them in the energy planner.
Check watts and sockets separately
If all four example loads run together, their assumed averages total 87 W. Use each device's actual maximum or startup requirement when checking the station's continuous output and its outlets; the 87 W planning average does not establish the peak. A kettle, heater or hot-food appliance changes the job sharply. Even a hypothetical 600 W heater used for half an hour adds 300 Wh, and it demands an output that can supply 600 W while it runs. Do not fold heating into a small checkout budget without checking the actual appliance and venue arrangements.
Check whether the terminal and router need USB or AC power, and whether a station's idle or power-saving setting could cut a lightly loaded outlet during trading. The settings guide explains why that can matter. Test your exact equipment and checkout sequence before relying on it for a paid trading day. Battery power also does not ensure mobile data coverage or a working payment service; decide how you will take payments if either fails.
Agree the site layout and recharge route
Ask the organiser what power is supplied, where your pitch sits and what equipment and cable routes are permitted. If you use a station, position it and its connections away from customers and weather exposure, within the exact model's documented temperature, ventilation and moisture limits. A portable battery does not make connected leads or appliances rainproof.
The UK Health and Safety Executive advises event organisers and users to account for power requirements, weather exposure and cable routes, including trip hazards and damage from traffic. Agree the layout with the organiser and use equipment suitable for the conditions. HSE event electrical safety.
Finally, plan the next reliable recharge. A larger battery may be easier than depending on a lunchtime top-up that the site cannot provide. If you carry the station from a distant vehicle, count its weight and all cables in the load. Start with the mobile-work route for model profiles, then compare the exact regional unit against your completed load list.