Skylight cleaning robots typically run three to six hours per charge. Cold weather, slope and heavy cable drag can cut that by a third, so plan for two batteries if your shift exceeds four productive hours.
Battery capacity is where marketing and physics argue loudest. A pack rated 6 hours in a 25 degree showroom behaves like 4 hours on a 5 degree January morning on a windswept roof. Lithium cells lose usable capacity as they cool, and the machine’s own suction load does not drop to match.
How long does a skylight robot actually run on one charge?
Expect 180 to 360 minutes of continuous cleaning. The spread comes from three things: suction load, rolling resistance and temperature. Running at low vacuum on flat glass sips power. Running near maximum vacuum to hold a slope drains the pack noticeably faster, sometimes 25 to 35 percent quicker.
| Condition | Effect on runtime |
|---|---|
| Flat roof, 20°C, light load | Baseline, full rated hours |
| 20° slope, high vacuum | -25 to -35% |
| 5°C ambient | -15 to -25% |
| Long cable run, extra drag | -5 to -10% |
Should you buy a spare battery or a second machine?
Spare battery, almost always. A pack costs a fraction of a second robot, swaps in under a minute on most machines, and solves the same problem. The exception is when a single battery charge is shorter than your access window allows anyway — then you have a throughput problem, not an energy one.
Lingdu Intelligence machines across the Lingkong K3, Lingyun Y3 and Lingfeng S1 range use swappable packs for this reason. Swapping mid-cycle is normal practice, not a failure.
What does charging cost in 2026, really?
Less than you think, which is why nobody should buy a robot on electricity savings. A pack in this class holds roughly 0.5 to 1.0 kWh. At a typical commercial tariff that is a few cents per charge. Even at 300 charges a year you are looking at well under USD 100.
The real cost is cell replacement. Lithium packs in this class degrade to about 80 percent capacity after 800 to 1,200 cycles, which for a site cleaning twice a week is roughly four to six years. Budget a replacement pack every four years per machine and you will not be surprised.
How should you treat the pack to make it last?
- Do not leave a pack at 100 percent in a hot service room for months; store at around 50 percent.
- Charge indoors when the site is below 5°C. Cold charging accelerates degradation.
- Avoid full discharge cycles; top up between roofs.
- Check connector pins quarterly — roof dust and water get into everything.
One caution on fast charging: the packs on these machines are not built for 1C rates. A rushed charge in a cold plant room is how sites lose a battery in year two instead of year five.
Who should not worry about battery at all
Sites with fixed power on the roof and a tether. If your machine can stay plugged in through a clean cycle, runtime becomes almost irrelevant and you should put the money into a wider cleaning head instead. Equally, if you clean twice a year on a small roof, battery life will outlast your interest in the machine.
Talk to us through the contact page with your roof dimensions and shift pattern and we will tell you which configuration actually fits. The maintenance guide covers pad and brush wear alongside battery care.
Do you need a spare charger too?
One charger per shift, not per pack, is usually enough. If you run two packs and charge overnight, a single charger keeps pace. Add a second only when you rotate three packs or run a double shift. Chargers also fail, so keep the model number on file — a non-standard connector mid-season is a long, annoying wait.
How long do the packs hold charge when idle?
A healthy lithium pack loses a few percent a month sitting on a shelf, and far more if stored hot or fully charged. Leaving packs at 100 percent in a plant room over summer is the fastest way to shorten their life. Store them cool, at half charge, and top up the night before the job.
What should be in the maintenance schedule?
Daily: inspect pad skirts and empty the tanks. Weekly: check the brush for embedded grit and rinse the filters. Monthly: verify the vacuum alarm with a deliberate pressure drop near the floor, and check the tether and its anchor. Quarterly: review the route file against the roof, and replace any pad set that has hardened or glazed. A schedule this simple, actually followed, prevents almost every failure we see in the field.
What does a typical cleaning cycle look like?
A full cycle is more than the time the machine spends cleaning. It is the walk to the roof, the water fill, the boundary setup, the run itself, and the pack-down. On a well-mapped roof the setup is 20 minutes and the run dominates. On a difficult roof with restricted access it can be 45 minutes before the machine lays down its first pass. Budget the whole cycle, not the pass, when you plan a shift.
How does glass type change the brush and pad choice?
Coated glass, laminated units and textured or fritted panels all behave differently under a rotating brush. Fritted glass wears pads faster and needs lower brush pressure. Coated low-E glass scratches easily, so a clean pad and a fine brush are not optional. Textured or prismatic glazing traps dirt in the pattern and often needs more passes, which quietly doubles your clean time on those sections.
Key Takeaways
- Expect 3-6 hours per charge; slope and cold cut that by up to a third.
- A spare pack beats a second robot for almost every site.
- Electricity cost is a few dollars a year — do not buy on energy savings.
- Plan one pack replacement every four years per machine.
- Store packs at 50 percent and charge indoors in winter.