What watt power solar panel to buy

[westwind28]

Hi,

Looking at buying a small solar panel for my deep cycle battery. Im looking at a 40 watt panel.

I would be staying on the boat for 2-3 days at a time. Charging a tablet maybe once out of the three days, maybe charging a phone and the rest for mast light, VHF and maybe charging the GPS. The interior lights are separate AAA battery portable lights, not wired in. So with this information would 40 watt panel be enough?

Boat will have an outboard (pullstart) installed in the near future.

 

[Tim Good]

Winter / summer? First change your mast light to Led if your anchoring. Your tablet won't need much and if it is summer only then 40w would be ok if positioned well rather than just getting it out on the odd occaisuon. Mine are high up over the stern and work all the time. Remember a small shadow will kill performance.

A roaming panel does have advantages though on a long cable when you can just plug it in and place it in the best position whilst sailing or at anchor.

Assume you'll get max 30w from it so maybe 2-3 amps tops. Figure you'll get charge for maybe 3-4 hours a day on average at full whack.

 

[JumbleDuck]

Hi,

Looking at buying a small solar panel for my deep cycle battery. Im looking at a 40 watt panel.

I would be staying on the boat for 2-3 days at a time. Charging a tablet maybe once out of the three days, maybe charging a phone and the rest for mast light, VHF and maybe charging the GPS. The interior lights are separate AAA battery portable lights, not wired in. So with this information would 40 watt panel be enough?

Boat will have an outboard (pullstart) installed in the near future.

Buy the biggest panel you can physically fit. There is no point on getting a smaller one, except to save not-very-much money.

 

[PaulRainbow]

Buy the biggest panel you can physically fit. There is no point on getting a smaller one, except to save not-very-much money.

I Agree 100%

 

[vyv_cox]

Buy the biggest panel you can physically fit. There is no point on getting a smaller one, except to save not-very-much money.

And a regulator. A big panel can overcharge a single battery on (rare) bright sunny days.

 

[PaulRainbow]

And a regulator. A big panel can overcharge a single battery on (rare) bright sunny days.

He'll need a regulator with a 40w panel.

 

[westwind28]

Summer,

and the seller advise that I buy a controller with the solar panel.

 

[westwind28]

Thanks for the info

 

[LadyInBed]

He'll need a regulator with a 40w panel.

But they are less than £20, so not a big outlay.

 

[JumbleDuck]

But they are less than £20, so not a big outlay.

Yup - any basic one will do just fine.

 

[Trundlebug]

Buy the biggest panel you can physically fit. There is no point on getting a smaller one, except to save not-very-much money.

+1
No such thing as too much power.
If you fit a suitable charge controller, it will cut out when the battery is fully charged or at the very least prevent overcharging.
So for days when it's dull, or raining you have a better chance of maintaining your battery(ies) if you have a bigger panel.

Measure the space available and buy a panel to fit.

 

[ghostlymoron]

+1
No such thing as too much power.
If you fit a suitable charge controller, it will cut out when the battery is fully charged or at the very least prevent overcharging.
So for days when it's dull, or raining you have a better chance of maintaining your battery(ies) if you have a bigger panel.

Measure the space available and buy a panel to fit.

or better still, get 2 to lessen the effect of shading.

 

[ex-Gladys]

or better still, get 2 to lessen the effect of shading.

+1... I have loads of space on Gladys' wheelhouse roof and put two 45W panels on to charge 330 AH battery bank, regularly get one panel shaded and still see around 2A at this time of year in those circs.

 

[westwind28]

ill share the ebay link of the panel im looking at, hope the summer comes back soon

http://www.ebay.co.uk/itm/302112522573?ssPageName=STRK:MESOX:IT&_trksid=p3984.m1559.l2649#shpCntId

 

[duncan99210]

The panels you link to are semi flexible, so they are designed to fit on to flat/curves surface and be either glued or screwed down. However, the junction boxes where the power lead exit the panels are fixed to the back of the panel, so you can't fix them down flat. Second problem is that they don't have holes at the corners to take screws, limiting your fixing to glue. Something like this might be a better bet http://www.ebay.co.uk/itm/20W-Watt-...207933&hash=item58e2f9f893:g:WwUAAOSwz71ZUj4R.

 

[vyv_cox]

Unfortunately those junction boxes look very vulnerable to being kicked off if the panel was screwed to the coachroof. My semi-flexible panel has a junction box moulded into the edge of the panel. It does not protrude upwards at all. It did cost a lot more than these but that was many years ago .

 

[whiteoaks7]

This info is still current I think: http://www.pbo.co.uk/expert-advice/solar-panels-everything-you-need-to-know-24455

 

[JumbleDuck]

I'll repeat a warning I've given before. You'll see a lot of semiflexible panels advertised as able to take "30^o" curvature, which they can't. It is (almost certainly) a misreading in China of "3%" curvature - someone didn't understand the difference between "0^o" and "^o/_o". If you try and bend them more than a little you will destroy them, as the PV cell wafers are bonded to the aluminium backing and will crack.

Solution: don't buy cheap panels with aluminium backs and expect them to bend.

 

[PaulRainbow]

Solution: don't buy cheap panels with aluminium backs and expect them to bend.

<snip>

Solar panels are a long term item, i have some from about '88 on the coachroof, so i think it makes sense to buy good ones and a good controller.

 

[JumbleDuck]

<snip>

Solar panels are a long term item, i have some from about '88 on the coachroof, so i think it makes sense to buy good ones and a good controller.

I think there are two ways to go. Either buy really good ones or really cheap ones. I went the latter way. This allowed me to get 2x50W on my coachroof for £100 and £150 - the cheap one from A.N.Ebayer and the more expensive from Photonic Universe. I didn't expect them to last long, and indeed the cheap one died last summer and I have just replaced it. The replacement cost £60. If I had bought really good ones I'd have paid.

The high quality alternative would have been 2x30W (shape constraints) for around £350 each. I'm happy to put up with occasional replacement because (a) the total cost of ownership is similar and (b) price per W is coming down - not only could I replace a £100 panel with a £60 one, my £150 panel now costs £100 from Photonic Universe.

Of course other might have different priorities - if I was crossing oceans I would go for higher quality and if I had room for solid panels I'd use the best I could afford there too. For me, though, semi-flexibles are a consumable, almost.