How long should the battery last between charges?

This depends on three factors, (a) whether the battery has been fully charged, (b) the number of hours of daylight (remember Robop switches on a Dawn and off at Dusk) and (c) the prevailing weather conditions, notably the wind speed. Over recent weeks we have been running life cycle tests which have shown that the battery packs are capable of powering Robop for 21 days. However, our recommendation is that Robop is charged every week.