As far as we know, starting and stopping or varying the charging power does not harm a vehicle's battery. There are many solar charging products on the market which perform a similar function.
Frequent changes to the rate of charge associated with solar charging, is similar in nature to the frequent change in power draw whilst driving. Normal driving will see the load rate rapidly shift between 0 and 100kW+ within seconds, whilst solar charging will only see a fluctuation not exceeding 1.2 - 11 kW, not more than once per minute. We do not believe this will harm a vehicles battery.
We are aware of rare cases where frequent stopping and starting of charging has lead to premature failure of the contactors (switches) in the charger (not the car). Charge HQ has several delay mechanisms to limit the frequency of stopping and starting eg on partly cloudy days. Please see Reducing Contactor Wear for more information.
