Solar Pannels

[Talmine]

I'm looking to buy a solar pannel to keep the batteries charged when I'm away from the boat(30ft yacht 20 hp engine, 170 amp hour house batteries and 50 amp hour engine stating battery) and help out with power demands whilst cruising. I was thinking about 30 watts. I'm not sure about their effectiveness and have been a bit surprised by some of the prices I've seen advertised.

Any advice on effectiveness, experience, type and a good supplier

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[VicS]

I rate my solar panel as one of my "best buys". Its only 5watts and keeps a small (40AH, I think) battery charged while I'm away from the boat. Otherwise charging is from an outboard but my demands are minimal.

30 watts will need quite a bit of deck space. If you want to charge two batteries simultaneously you will need a split charging arrangement as well as regulation. You could of course have two smaller panels, one for each battery. Fit fuses as well.

Others on this forum will maintain that solar panels are c**p. Perhaps they bought cheapies.

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[HenryB]

I, too, rate my solar panels highly. They are a total of 90 watts, feeding 400 ah of batteries. I use them in the Med where the fridge consumes the most power. With care they allow me to maintain battery levels without needing to run the motor.
From my experience they produce half their watt rating in amp hours per day - i.e. a 60 watt panel gives 30 amp hours, that's summertime in the Med. One oddity is that they are less efficient at higher temperatures (they convert light not heat) so they might produce a higher output if somewhere cooler than the Med.

Regards,
Henry

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[HenryB]

I, too, rate my solar panels highly. They are a total of 90 watts, feeding 400 ah of batteries. I use them in the Med where the fridge consumes the most power. With care they allow me to maintain battery levels without needing to run the motor.
From my experience they produce half their watt rating in amp hours per day - i.e. a 60 watt panel gives 30 amp hours, that's summertime in the Med. One oddity is that they are less efficient at higher temperatures (they convert light not heat) so they might produce a higher output if somewhere cooler than the Med.

Regards,
Henry

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[Gunfleet]

I have a 32 watt Unisolar flexible panel and 220 amp/hour battery bank. The panel is about 3ft 6 long and 14 inches deep. You can tie it to the guardrails like a spray dodger, over the boom or over the canopy. In direct sunlight it outputs about 2 amps, in overcast about .5 of an amp. It allows me to leave the navtex on all the time without feeling I'm wearing out the battery when I'm not there. Ideally a second panel of abt 30 watts would give a great deal of flexibility. Neither of course would allow you to run a fridge for long - 5 amps when it's drawing current. I found the best price/service deal around was at ampair, though ymmv

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[yoda]

In general people who have solar panels and understand that they provide a small charge over a long period of time are very happy with what they have. After years of struggling with batteries going flat I fitted a 10w panel and haven't managed to flatten a battery since. The size you buy will be largely determined by the area of deck available to fit he panel on however the very flexible ones (as another poster has described ) can overcome this to an extent. What they are very good at is ensuring your batteries are fully charged when you get to the boat. What they won't do is recharge like an alternator will. Get on, understand it's limitations and enjoy fully charged batteries every time you get to the boat.

Yoda

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[poggy]

Hi,

With the amount of battery power you have on board, I am surprised you need solar panels unless you have a lot of equipment using a lot of power. Rather than use solar panels which are expensive if you want a decent output and also need to be in the right place to be the most efficient, I use a battery pack which I take home with me and keep charged. This provides a lot of extra domestic power and also has the benefit of being able to start the engine if necessary. They only cost around £30.00.

This is only my opinion of course and suits my needs.

Poggy

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[Gunfleet]

Hi Poggy,
you wrote <<With the amount of battery power you have on board, I am surprised you need solar panels unless you have a lot of equipment using a lot of power>>
but that's a common misconception. No matter how big the battery bank the amount you take out has to be put back in... otherwise you will keep the batteries permanently undercharged and they will quickly fail. Having a solar panel charging them while you are absent discounts this effect - 5 days times 10 hours at .5 of an amp = 25ah. So if your 200ah battery bank (2xleisure batteries) is depleted by 10% you should just about put it back by the time you return. No doubt the engineers will chip in with voltages, batteries building resistance as they reach 12.6 or so volts and all the rest of it, but that's the theory. Of course if you were in the Med you could look forward to really useful power out of the same panel - perhaps 5 days times 10 hours at 2 amps = 100ah. A real weekend's worth of electricity, though possibly not enough if you like cold beer!

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[dovekie]

I agree with the majority of replies here. About 10W panel per 100Ah battery capacity seems to keep them topped up in average UK summer weather without boiling them. They are real "fit and forget" pieces of kit and my last one lasted 10 years. Eventually it delaminated a bit and the junction between panel and cable corroded. I've protected my new one better.

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