To fully charge a solar powerbank, it could take even a few days. Total charging time depends on many factors, like the capacity of powerbank, the size of solar panel and also on the weather conditions.
Solar powerbank doesn't need a direct sunlight for charging. But without direct sunlight, it takes much longer to reach the full charge.
Powerbanks with a lower capacity (5000 mAh or 10000 mAh) can be often charged with direct sunlight within 12-24 hours, but sometimes the charging may be even faster.