It's very hard to make any kind of guarantee as every vehicles power consumption when not in use is different.
Typically these panels are intended to keep a battery healthy during periods of non use, if you have any extra systems in a vehicle taking extra power (an in vehicle video recording system for example) then there is a high likelihood that more energy is being consumed than replaced and the battery will eventually drain and become flat.
To give an examples of how much power the panel places into a battery.
At maximum output (ideal conditions) the panel would provide 137 milliamps per hour.
If we assume an average day of 12 hours this will generate approx 1.65 Amps per day.
As long as the energy removed from the battery does not exceed that amount it will keep the battery at a sustainable level.
If you wished to charge the battery you mention from flat to full it would take 57.5 (12 hour) days, however this does not take into account energy lost through natural dissipation.
Obviously in winter months the hours of daylight are much shorter so this would adversely affect the amount of power being generated.
Date published: 2017-09-20