Solar Panel Questions

[gregoire.poirie]

We are looking to add solar panels on our live aboard, 47" Beneteau sailboat and wondered if a good target is getting 400w in 4 panels. Since we have most of modern conveniences, we want to offload expenses when on shore power and want to use the gen for backup to keeping dry battery bank fully charged when cruising.

Suggestions?

[Suijin]

You need to work up a energy budget (ideally from real world experience) forecasting what your needs are.

More information on your battery bank (type of batteries and total amp hours) would also be useful. A general target is to have more watts than amp hours, but that's just an average.

How much time do you spend away from the dock? Long periods anchoring? Long passages?

[gregoire.poirie]

I need to correct that we only want to use the 8.5w generator as a backup only, and depend on solar when cruising or even out on a mooring. Goal is to outfit her for long passages and extended time off shore power.

[Mike OReilly]

What Suijin says … work up an energy budget to see how much you need. This will answer your question. Hard to answer without knowing what you use.

But another way to go at it is to simply maximize your solar production. If you can reasonably add more panels, then why not? Not many full-timers ever complain about having too much passive electricity production.

I have 400 watts of solar in four parallel panels, all run through a single MPPT controller. I also have a 400 watt wind gen. I carry a 1000 watt gasoline generator as the final backup. During my last season I ran the gas generator for 3 hours over six months — most of this at anchor or underway.

If I could add more panels, I probably would. But my current system keeps my batteries (320 amp-hr) topped up almost all the time. Solar contributes most (~80%), but wind is a useful compliment.

[Kenomac]

Add four Solbian 100w flex panels to your bimini.

[Paul L]

As mentioned earlier your energy budget is key to answering your question. With the expected consumption and knowing how much room you are willing to dedicate to the panels and you can make a good decision. If you are planning tropical cruising, keep in mind that your refrigeration will consume much more than in the cooler climes (it will also consume much more when you are full-time onboard).
If you have room for 4 panels, then I'd go larger than 100watt. A 125watt is not much harder to mount.

[barnakiel]

Depending on where and how you sail, 400W will vary from marginal (still, worthwhile) to quite some portion of your total needs.

We have 150W in a 26', VERY VERY basic boat (no fridges, no AP, no navionics). Our 150W is (nearly) enough in this set up. But this set up is a niche. We are like say 1% of the population.

Last year I installed a 1000W package into a small cat. I also have a job waiting for me in the Indies to set up a 2000W+ kit into a bigger cat (61). In both cases this is up to 25% of their (very typical) daily load.

You may like to invest some online time into researching the variety of panels and regulators. As well as in researching the factors that determine how much of the nominal values you get depending on the variable factors (temperature, panel angle, panel shading, etc.). Depending on what you buy and how you wire things, your 400W kit may effectively equal anything from 200W to 600W. Good optimisation and quality components make plenty of sense.

Cheers,
b.

[Zai]

I can give you as an example of my set up.
I have a 37 foot Bavaria and I have 600watts of solar on an arch.
I have 600 amp hour battery bank.
I also have a Silent Wind wind generator (max 400 watt).
I have an 2500 watt inverter.
I run a 12 volt watermaker almost every day, have a laptop, a tablet and a mini router plugged into AC all of the time.
I have only a refrigerator (no freezer yet).
I have several 220 volt appliances which I use periodically (like a wet dry vacuum etc.
Sometimes I warm water from the batteries through the inverter.
If I manage the power usage right we are self sufficient, but it requires that I plan accordingly, for example if I will warm water with the batteries it must be done early in the day, so as to ensure we have full batteries at the end of the day.
The wind generator is basically only helpful when there is wind through the night.

[Olorin]

I'd say maximize your solar.
We have 1250 watts of solar panels and 1000 AHr batteries.
We have a frig, freezer, lots of electronics, 2 computers, 2000 watt inverter and a 12 volt water maker. (18 amps at 12 volts yields 16 Gallons/60 liters per hour)
When I get back on the boat I want to rig up another 750 watts so that I will be energy rich. I've got the space on top of my bimini as I'm a catamaran.

[travellerw]

I think Mike's post was spot on (referring to Suijin).. An energy budget is essential.. However he highlights what I failed to realize.. YOU WILL USE MORE THAN YOU THINK, and keep using MORE as you add more capacity.

We are a family of five with a fridge, freezer, kids electronics and 2 laptops. We have 900W of solar, 400W of wind and 660AH of batteries (should have had more). We make it work, but as our batteries have aged we need to run the generator 2 hours every 2 days. That will only go up and we expect a maximum of 4 years battery life (Lead acid 6V golf cart batts).

Another piece of advice (after living aboard for 2 years).. I would look at bigger panels with higher voltages (maybe 3 150W panels) and run each one to its own MPPT controller. Not only will this give you a better harvest with less shading issues, but it provides redundancy. If a single circuit "craps the bed", you still have 2 to live off of!

[travellerw]

Originally Posted by Olorin

I'd say maximize your solar.
We have 1250 watts of solar panels and 1000 AHr batteries.
We have a frig, freezer, lots of electronics, 2 computers, 2000 watt inverter and a 12 volt water maker. (18 amps at 12 volts yields 16 Gallons/60 liters per hour)
When I get back on the boat I want to rig up another 750 watts so that I will be energy rich. I've got the space on top of my bimini as I'm a catamaran.

Jesus man... We are on the same boat and I can't imagine WHERE I would put 2000W of solar on her (without serious shading). I already have one panel on the passage between the tramps..

I would love to see pics when you are done.. I'm imagining your bimini full of panels from the traveler to the dingy davits.

[Quadrille in JB]

An energy budget comes first as stated repeatedly.
As unshaded space is always at a premium, use the most powerful and efficient panels made. I use the 360watt Sunpower panels that are 40.5"x60.5" that can actually produce 360w with a Victron 100/30 mppt controller. Why use multiple smaller panels when you can get a lot more bang (or watts) for your bucks.
BTW-due to Sunpower corporate policies these panels are often hard to get. I can get get them for you. PM me if you'd like a quote.

[UFO]

Originally Posted by gregoire.poirie

We are looking to add solar panels on our live aboard, 47" Beneteau sailboat and wondered if a good target is getting 400w in 4 panels. Since we have most of modern conveniences, we want to offload expenses when on shore power and want to use the gen for backup to keeping dry battery bank fully charged when cruising.

Suggestions?

Having run a few different solar systems on houses, rated output and what you get are two very different things with a lot of variables involved. Get as much as you can afford in space and $ and make sure its quality kit - Its a very false economy otherwise.

Get the highest rated (W) panels you can - I've heard good things about:

Kyocera KU265-6MCA 265 Watt Multicrystal Solar Modules


Have Fun

[travellerw]

Originally Posted by UFO

Having run a few different solar systems on houses, rated output and what you get are two very different things with a lot of variables involved. Get as much as you can afford in space and $ and make sure its quality kit - Its a very false economy otherwise.

Get the highest rated (W) panels you can - I've heard good things about:

Kyocera KU265-6MCA 265 Watt Multicrystal Solar Modules


Have Fun

Hmm we get "rated output" (actually more) at noon with our "ele cheapie" panels from Amazon. Actually we know tons of cruisers using cheap panels and they also get the "rated output" (of course rated output is full sun with batts that can take it)...

Maybe there are crap panels out there but we haven't heard of them amoung live aboards. I think most of the panels sold in the USA are meeting or exceeding thier rated output..

However... efficiency is completely different.. The Sunpower panels listed above will beat my panels by %8 (easily).. Thats a lot more energy for the space.. but a huge premium for that %8.

[Kenomac]

The OP has a generator, he doesn't need 1000-2000W of solar on a 47ft boat. We have only 450W, which is sufficient to go 8 days and sometimes longer without running the generator. He can use the generator to do a one hour bulk charge every other day or so in about an hour, and then use solar to top things up.

He doesn't need to spend money to build a floating a solar farm when he already owns a generator..