A watt-hour (Wh) rating is the amount of energy a battery can store, worked out by multiplying its voltage by its capacity in amp-hours. The bigger the number, the more energy the battery holds, which is why it’s used to set safety limits on lithium-ion batteries, such as the rules for what you can pack for a flight.
Working it out
The rating is often printed on the battery or given in the manual. If it isn’t, the UK Civil Aviation Authority gives the sum: volts × amp-hours = watt-hours. If the capacity is in milliamp-hours (mAh), multiply by the volts and divide by 1,000.
- An 18V tool pack rated 5Ah: 18 × 5 = 90Wh.
- A 36V e-bike battery rated 14,000mAh: 36 × 14,000 ÷ 1,000 = 504Wh.
The CAA notes that batteries under 100Wh are common in phones, laptops and cameras, and that power tools and large power banks are where you’ll find 100Wh to 160Wh.
At Wigwam
The number that matters in a Wigwam unit is 160Wh:
- loose lithium-ion batteries of 160Wh or less, such as spare tool packs, can be stored;
- a battery over 160Wh can be stored only if it’s built in and can’t be removed, so a removable e-bike battery like the one above goes home with you, even when it clips into the bike;
- power banks and portable chargers can’t be stored, whatever their rating.
These limits keep the energy stored in any one unit small, which protects your belongings and everyone else’s. If you can’t find the rating on your battery, call us on 0800 2545585 before you bring it and we’ll help you check.
Related terms
Related questions
- Can I store an electric bike, e-scooter or lithium batteries in a storage unit?
- What goods are prohibited from being stored at Wigwam?
Further reading
- UK Civil Aviation Authority: Pack right. Safe flight.