Solar Panels

[DustyDave]

I bought a boat last year thinking I'd quite happily be doing 8 hours of cruising every day. Now in the second year of owning it I've found I enjoy doing about half that before stopping (and sometimes only a couple of hours). Now facing the reality of living with lower cruising time I'm looking at installing a solar panel or two. My question is how many do I need. I don't want to pay for a setup only to discover it's nowhere near enough.

 

Here are some details:

 

440ah battery bank

 

Usage:

Lights - all LED (or will be soon). No more than 4 on at once (3 hours a day).

Fridge - 240V on all the time

LED Telly - 45 watts max (have it on low power setting so probably much less). Around 4 hours a day

DVD Player - 15 watts. Around 4 hours a day

Water pump for hot and cold water (shower, not bath).

 

I'm a weekend user so the aim is I'll always be coming back to a topped up set of batteries. I still want enough solar power to cope with my holidays though.

 

Is 100watts enough or should I be looking at 200watts (or more)?

 

Cheers,

 

Dave

[cotswoldsman]

In a summer like this year I would be looking at 200 watts

[Proper Job]

The one thing to think about is how much room do you have on the roof.

 

I've got 2 x 85W panels. They meet my power requirements in the Summer, but it's a lot lower than yours.

 

As a weekend user, they would keep the batteries well charged during the week while you're away.

 

2 - 4 hours cruising per day, with topping up from panels when the engine is off? 2 x 80'ish W panels should do you fine. Get a 20A controller and then you can add another panel in the future if required/space is available.

[Richard10002]

I've bought a 100w panel on the basis that I should come back to full batteries after leaving the boat for 3 days or so. I expect to then use the engine or generator to top them up on the days I'm on board.

 

The panel says it has a max of just over 5Amps, so I'm guessing it might average 2 or 3 amps on a summer day for 9 or 10 hours, so 20 or 30 Ah a day. Not enough to replenish a night of my usage, which seems to around 60 to 70 Ah.

 

To achieve your goal, I'd say you 200 to 250 watts of solar

 

But that's still a bit of a guess.

[matty40s]

In a summer like this year I would be looking at 200 watts

In a summer like this I would also recommend an umbrella over them.

[Arthur Brown]

If you intend to run the fridge when you are not on the boat you need a much bigger battery and much bigger solar cells as the fridge could well use 100amphours during a day and you have to put that back over a 5 - 7 hour period of strong sunlight.

 

If you intend to turn the fridge off when the boat is unoccupied you will use lots less power.

[DustyDave]

Thanks for all the replies. I didn't realise the fridge used so much power. It's only on when I'm using the boat (and only when I'm on it for more than one night). Given the absolute rubbish weather I'm very tempted to get a generator first and save the solar panel purchase until next year (spent too much on the boat already this year).

 

Dave

[Richard10002]

Thanks for all the replies. I didn't realise the fridge used so much power. It's only on when I'm using the boat (and only when I'm on it for more than one night). Given the absolute rubbish weather I'm very tempted to get a generator first and save the solar panel purchase until next year (spent too much on the boat already this year).

 

Dave

 

New to narrow boating in September last year, but a "veteran" of Mediterranean anchorages, with only the engine to charge the batteries, a Honda eu20i was top of my list of purchases..... Then an inverter/charger 2500/70 to replace the existing 25A charger, and only then, a 100W solar panel.

 

I haven't fitted the panel yet but, whatever the state of the sunshine, I can fire up the genny, and get about 80-100 Ah into the batteries in a couple of hours, assuming the batteries have the capacity, and that this doesn't exceed around 80% SOC - which is where the solar will come into its own

 

An external alternator regulator is on the list somewhere, as is a NASA BM-2, but these can wait until I've built a sofa bed in the saloon, and fitted the Rinnai water heater somehow.