How much solar for a trickle charge?

[colind3782]

I want to get a small solar setup purely to keep the four batteries (300 amp total, or thereabouts) topped up while we are away from the boat for weeks at a time. We're in Empuriabrava so no problem with sunlight (usually!) and I don't want a large array as I would disconnect the panel and stow it away when we're aboard as we have plenty of shorepower.

To clarify, we don't need to charge the batteries at anchor or anywhere else and I would like a small simple setup if possible. What sort of wattage would I need?

Edit: I've looked at youtube vids and there are far too many to wade through before asking here. If there is a recommended youtube vid or book, please shout up

 

[Bobc]

A 50w panel should be fine. I have an EP Solar dual battery controller, which will put charge into both banks, and you can set the percentage to each bank (I usually have 80% going to the house bank, and 20% going to the engine battery.

Controller details here

 

[biscuit]

I have had aa 30w panel, for the last 6 years, on a swinging mooring in W. Scotland, and it keeps the 3x 100 amp batteries topped up between trips.

 

[vyv_cox]

I have had aa 30w panel, for the last 6 years, on a swinging mooring in W. Scotland, and it keeps the 3x 100 amp batteries topped up between trips.

Similar for me. In North Wales I had a 20W panel mounted on the wheelhouse horizontally feeding 2 X 120 Ah house batteries and a 10W panel lying behind the windscreen feeding 1 X 120 Ah starter battery. This kept batteries up to scratch for a couple of years.

 

[thinwater]

50W in my case. You could go smaller, but 50W will also top up the batteries over a week if you run them down. A simple controller will do. And read up on fusing requirements.

BTW, the batteries are 300 Ah, not 300 amp. Amps and watts are rates, amp-hours and watt-hours (Wh) are capacity. Cox, unsurprisingly, has this right.

 

[colind3782]

50W in my case. You could go smaller, but 50W will also top up the batteries over a week if you run them down. A simple controller will do. And read up on fusing requirements.

BTW, the batteries are 300 Ah, not 300 amp. Amps and watts are rates, amp-hours and watt-hours (Wh) are capacity. Cox, unsurprisingly, has this right.

Sorry, I do know the difference between amps and Ah. Put it down to old age and fat fingers!

 

[vyv_cox]

50W in my case. You could go smaller, but 50W will also top up the batteries over a week if you run them down. A simple controller will do. And read up on fusing requirements.

BTW, the batteries are 300 Ah, not 300 amp. Amps and watts are rates, amp-hours and watt-hours (Wh) are capacity. Cox, unsurprisingly, has this right.

Should have said, no controller in my case.

 

[William_H]

I think the answer will come out of OP's head. Usually you wouild say the bigger the better bu then you will need a controller to avert over charge. Then you have to have a place to stow the panel when not in use. Perhaps 10w would be useful. Fit diodes to pos output to direct charge to presumably 2 battery banks. Fit diodes physically near battery terminals so no need for fuse. ol'will

 

[colind3782]

I think the answer will come out of OP's head. Usually you wouild say the bigger the better bu then you will need a controller to avert over charge. Then you have to have a place to stow the panel when not in use. Perhaps 10w would be useful. Fit diodes to pos output to direct charge to presumably 2 battery banks. Fit diodes physically near battery terminals so no need for fuse. ol'will

You wouldn't want to see what's in my head! Storage isn't a problem as our marina berth comes with a trastero (storage shed). I have worked out the routing but I will have to fit a deck type plug and socket to be able to disconnect the panel when not in use. Recommendations?

Thanks for all the input so far.