How long does the solar charge last?

Assuming the battery is fully charged and relatively new (within 12 months of purchase), the unit will stay lit continuously for about 1.5 hours on Auto mode, and 10 hours on Dusk-To-Dawn mode. Be advised that brightness will begin to diminish (i.e., dim) as the battery discharges. Once the battery is fully discharged, allow more time for it to charge to sufficient levels. (Otherwise, the unit may not activate as expected the following night). To fully recharge batteries, place the gutter light in direct sunlight for a period of 2-3 days, which will allow the battery to charge via solar power without discharging at night.