It is the question that decides whether someone buys a cordless lamp or not, and most product pages answer it badly — with a single number that turns out to mean the lowest brightness setting nobody actually uses.
Here is the honest version, including where the numbers come from and what they do not tell you.
Two numbers, and only one is on most listings
Battery capacity is given in mAh (milliamp-hours). Runtime is given in hours. They are related, but capacity alone tells you very little, because runtime depends entirely on how hard the lamp is driven.
A useful rule: a rechargeable lamp's stated runtime is almost always measured at its lowest brightness. At full output, expect somewhere between a fifth and a tenth of the headline figure.
Our own listings give the range rather than the flattering end. The Cordless Aluminum Table Lamp carries 2600 mAh per lamp and runs approximately 8 hours on high, up to 100 on low — a 12× spread, which is typical and is the whole point. The Mini Cordless Bedside Lamp is quoted at 10 to 72 hours for the same reason.
What that means in practice
Match the number to how you will actually use the lamp:
- Bedside, low setting, an hour a night — a lamp rated 10 to 72 hours lasts weeks between charges. This is the easiest duty cycle a battery lamp can have.
- Dinner table, mid brightness, three hours — several evenings per charge.
- Sole light source in a room, full brightness, all evening — you will be charging it every day or two, and you will resent it. This is the use case cordless lamps are worst at.
The lesson is not that the batteries are small. It is that cordless lamps are accent and task lighting, not a replacement for a room's main light. Used as accents they are close to maintenance-free.
Charging
Most current lamps use USB-C. Charge times run roughly 4 to 6 hours from flat — the aluminum pair takes about 6 hours over Type-C with the cable included, the mini bedside lamp 4 to 5 hours at 5V/2A.
Two practical habits worth forming:
- Charge them together, on a schedule. If you have three or four cordless pieces, pick a night. Chasing each one as it dies is what makes people give up on the category.
- Charge before an occasion, not during one. A lamp you top up the afternoon before a dinner will not be the thing that runs out at 10 p.m.
How long does the battery itself last
Different question, and the more important one for a $200 fixture. Lithium cells degrade with charge cycles rather than with time on the shelf. In normal household use — a few charges a month — a well-made lamp should hold useful capacity for years, with gradual shortening of runtime rather than a sudden failure.
Things that shorten it: storing the lamp flat for months, leaving it permanently plugged in at 100 percent, and heat. If you put a cordless lamp away for the season, store it part-charged rather than empty.
Are cordless wall sconces worth it?
The trade you are making is explicit: you give up unlimited runtime and get placement freedom. If the wall you want lit has no box and no outlet — behind a sofa, at the end of a hallway, above a bed — there is no alternative that does not involve an electrician.
Used as intended, at moderate brightness, for the hours you are actually in the room, a battery sconce is charged occasionally and forgotten in between. Used as a room's primary light, it will disappoint. The full argument is in renter-friendly wall sconces.
Getting more out of a charge
- Run it dimmer. The single biggest factor, by a wide margin.
- Use the timer if it has one. The Rechargeable Swing-Arm Picture Light switches off after a set run, which stops it burning charge on an empty room overnight.
- Warmer color temperatures often draw slightly less power than the coolest setting on the same lamp.
- Turn it off. Obvious, and still the thing people forget.
Common mistakes
- Reading the headline runtime as the real one. It is the low-brightness figure.
- Buying cordless for a room's main light. Wrong tool.
- No charging routine.
- Storing them flat for months.
- Running at 100 percent when 40 would look better anyway.
Run them dim, charge them on a schedule, and use them for what they are good at. The full range is in cordless and rechargeable lamps.