Hi Denise -
You need to relate your question to how you define "help trickle charge the batteries" in terms of what you are using them for. The following is copied from my post #256 here:
https://ericsonyachts.org/ie/threads/chesapeake-ericson-club.17137/page-13
Bob
Almost anything from Will Prowse is really good (
https://diysolarforum.com/members/will-prowse.1/) and there are a ton of other good resources online.
But it always starts with estimating a solar budget which means figuring out what you will have consuming power and for how long. We don't have electric galleys or AC and can switch most of the lights to LED, so we don't need lots of watts. Below are some fairly conservative numbers from my notes and what is below that is copied from my own numbers so you can use them as a place to start:
3W LED nav light bulb replacements (worst case each)
4.8W Marine Beam mast head and steaming light (2W for just steaming without deck light)
1.5W LED Interior bulb replacements
18W iPadPro11 (mine),30W MacBook, 87W MacBookPro, 85-150W Full MiniMac
.55A/6.6W standby mode for Standard Horizon GX6000 radio. Receive (max) .9A/10.8W, Xmit 5A/60W, Hailer 2.1A/25W
12W B&G Vulcan 7 chart plotter
Anchoring at night and using lights for 4 hours/night, I'd need about 386 Wh/day or 386/12= 32A:
(Anchor light 11 hours times 2W = 22 Wh) + (4 hours times 3 interior lights = 13.5 Wh) + (4 hr iPad = 72Wh) = (24 hours of radio X 6.6W = 158Wh) + (10 hours chart plotter X 12W = 120 Wh)
I currently have two 100 Ah lead acid batteries and don't want to discharge more than 50% so this can go without sun or charging for 3 full days. There likely will not be enough left to start the motor but the batteries won't be damaged in the worst case. For a normal weekend with some use of the motor (50A alternator times number of hours of use) and existing 50W solar it would be fine.
We are far enough north and cloudy often enough that my solar notes show that per day we should collect at least three times the watt hours a panel is rated at, so would average 150W with my existing panel. Obviously, hard will collect more than flexible, sunny summer days will be more than cloudy or in the winter, etc, but this is a place to start an estimate from. If I'm using the boat for weekends, the 50W panel is enough to recharge the batteries during the days not in use, especially if the motor is used to get to and from the dock.
If I wanted to stay out I would need to turn off the radio and chart plotter when possible &/or put another 100W panel out. I have two 175W hard panels in the shed (350W total) for when I go on a longer cruise and plan to just hang one or both from the life lines.
Last note is about buying stuff: There are all sorts of kits and places happy to take your money, but you can save a LOT by Googling reviews for what is available and comparison reviews. My system has:
$69.99 Richsolar 50W 12V ETFE flexible solar panel. It's cheap enough to replace every few years.
$47.95 HQST 20A MPPT controller. This is big enough to connect one of the big panels I have but not both. I only need one.
$12.53 Two bulkhead glands to run the wire through the cabin roof. Only used one.
$9.98 For 5 pair of RENOGY solar connectors
$5.36 Solar connector tool for assy & disassembly
$15.95 Solar connector pin crimping tool
$161.76 Total
Rather than buy cable, I made my own using Anchor Wire tinned marine grade 12/2 AWG Duplex. This is a much less expensive and better tailored approach. When I go to use the 175W panels I have the solar connectors and always have wire on hand so will be able to do the install very quickly.
LOTS of industrial velcro:
Panel installed with the bulkhead in the lower left before cleaning up the exposed wiring shows the RENOGY solar connectors:
Using coat wire to pull the cable behind the trim so it won't show:
Mounted the MPPT, breaker, and a directional switch to each of the batteries on a piece of aluminum: