Are all Boat Lift solar chargers under powered?

jglwkl

We bought a lake property last year and we are loving it. However, I've found that our solar-charged battery-powered boat lift isn’t as effective as I would like it to be. I can lower / raise our 19 ft deck boat (~2,200 lb) about twice per day before running out of battery power. Installed a new battery and tried a third battery with the same results.

We have a 12VDC Duracell MARINE & RV SL127MDP Dual Purpose battery. Don't know the Brand/Model or output wattage of the charger. I do not have a charger controller. We have a ShoreStation aluminum frame boat lift and a LiftTech DC remote Wireless Gen1 winch (12 or 24 volt).

Bottom line – I’m looking for the most efficient (e.g., highest number of Down / Up cycles per day) solar charging system for our lift. We have a lot of waves at our dock, so we prefer to use the lift instead of having the boat get pounded on the dock. Our best case would be to lower the boat fully in the morning, raise and lower it as needed during the day (raised just enough to hold it in place), and raise the boat fully in the evening.

First - I understand that solar is not an exact science and many variables such as sun angle, cloud cover, exposure time all have an effect on the efficiency of any given solar charging system. I also understand that more powerful chargers require larger panels, and so some practical / safety limit must be considered when mounting one on a boat lift. 

BUT -  I've looked at many articles and products online, and have become quite confused about what is ‘needed’ for an efficient system .vs. what is currently available.

The battery manufacturer recommends a 8A – 16A (between 115W – 230W) charger and a programmable controller, based on the battery's maximum charge rate (e.g., a standard 100Ah battery charges at ~10A).  However, most online products are only in the 10W - 40W range, and even the 'best' ones talk about the number of cycles per week rather than per day. Some even say that they've never had problems using a 12V 20W system! So, it appears that I may have some unrealistic expectations, but I want to know why. Aren't there any solar chargers made in a size suitable to mounting on a boat lift that are powerful enough to charge my battery at the manufacturer's recommended rate? I'm a retired computer engineer, not an electrical engineer, so I don't understand all of the intricacies of the electronics, but it seems that what the industry is offering is far less than what might be desired.

A secondary question is "how large (dimension) of a solar panel can I put on a lake dock before wind becomes a concern?"