Solar panel question

It always amazes me how threads wander away from the original question, however: I totally agree the controller will be rubbish (I tested some of these once for PBO if you can find the article) but otherwise you should be able to get crystalline panels for about £1 per watt. It's still true that only crystalline panels will have the best energy conversion per unit area for us yachties.
 
Has anyone used these: https://www.ebay.co.uk//itm/132337008784 ?

They look like a good deal at a reasonable price - and there's the potential for improving on the price by buying when I'm in Hong Kong in January! But are they any good? I'm looking for a cabin top mount with two panels - the more the merrier, but I'll be limited by price. The panels must a) be slightly flexible to take up the curve of the cabin top and b) be OK for walking on - they'll be located near the mast, so in an area that takes some foot traffic.

Comments?


Don't bother buying in HK - buy direct off Aliababa.com and have the ship them to you. I have just replaced the charge controller you showed with a more expensive MPPT controller. While the old controller was fine the new MPPT one has increased the output from my panels by 30% or more. (The reason for the upgrade was to allow me to increase the number of panels - having changed the controller I'm re-evaluating the need for an extra panel)

try here: https://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=Solar+panel

I am amazed at how much markup you are expected to pay on solar stuff in the UK. Buy direct from china!.Even if you have to pay HMRC their cut you will save loads.
 
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Don't bother buying in HK - buy direct off Aliababa.com and have the ship them to you. I have just replaced the charge controller you showed with a more expensive MPPT controller. While the old controller was fine the new MPPT one has increased the output from my panels by 30% or more. (The reason for the upgrade was to allow me to increase the number of panels - having changed the controller I'm re-evaluating the need for an extra panel)

try here: https://www.alibaba.com/trade/search?fsb=y&IndexArea=product_en&CatId=&SearchText=Solar+panel

I am amazed at how much markup you are expected to pay on solar stuff in the UK. Buy direct from china!.Even if you have to pay HMRC their cut you will save loads.
Thanks for the pointers. However, the attraction of buying in HK is because my wife has contacts with the renewable energy community there, and as Shenzen (where a lot of the Alibaba suppliers sell from) is just over the border, I'd expect her to be able to access good deals - perhaps even adding our requirements to a much larger order and thereby qualifying for the lowest prices; there's a big difference between one-off prices and 100+ off! . I'd expect anything that can stand up to Hong Kong's climate to be OK on a boat! Totally agree that market prices in HK tend to be high by Chinese standards, and there's no DIY to speak of - my Hong Kong relatives are amazed at the number of jobs we do like decoration, engine maintenance etc. - they'd never consider DIY, because labour is cheap, so there's little incentive for it.
 
One cell covered means no output, so long panels aren't great, a single rope or shroud shadow cuts off the output. Two or three smaller ones on each side are much more better.
 
One cell covered means no output, so long panels aren't great, a single rope or shroud shadow cuts off the output. Two or three smaller ones on each side are much more better.

Sorry, but that's absolute rubbish.

+1... my previous 2x 45W panels regularly produced 3.5A with a jib sheet shadow across one...

Agreed. There's a lot of rubbish talked about reduction of output by shading. My small panel is often partially shaded but continues to produce useful output.
I think the point is that older solar panels were susceptible to severe degradation by small shadows because the cells were all connected in series, so blocking one cell blocked the output from the whole panel. Modern panels have a greater poutput from individual cells, so the individual cells connected in parallel and series, so blocking one cell only partially blocks the output of the whole panel.

Another point is that shadows - especially shadows from objects like ropes or wires - are rarely solid. There is sufficient irradiation in the shadow for the cell to still produce an output, albeit a reduced one. I note that the cells on my roof at home provide SOME output even under heavy overcast, and a cell that is producing output is one that will not block the output from adjacent cells (I think - less certain of this bit!)
 
I think the point is that older solar panels were susceptible to severe degradation by small shadows because the cells were all connected in series, so blocking one cell blocked the output from the whole panel. Modern panels have a greater poutput from individual cells, so the individual cells connected in parallel and series, so blocking one cell only partially blocks the output of the whole panel.

Another point is that shadows - especially shadows from objects like ropes or wires - are rarely solid. There is sufficient irradiation in the shadow for the cell to still produce an output, albeit a reduced one. I note that the cells on my roof at home provide SOME output even under heavy overcast, and a cell that is producing output is one that will not block the output from adjacent cells (I think - less certain of this bit!)

The statement i referred to as rubbish was that "One cell covered means no output, so long panels aren't great, a single rope or shroud shadow cuts off the output. Two or three smaller ones on each side are much more better."

I'm afraid that is completely wrong.

My coachroof panels were installed in 1988 and are fitted beneath the boom, so suffer badly with shading. They still produce a useful yield. They are however, quality Solarex panels. You are correct that modern panels are more efficient than older ones. My current aft mounted 100w panels are the same physical size as the former 60w panel and still produce a higher yield than previous 100w panels.

As for output under overcast skies, looking overhead at this very moment in time, the sky is a very unpleasant solid grey. My panels are still producing 4a.
 
Hey AntarcticPilot's, I have not used this product, but I had a thought to buy this but later on when I compared this product with many other panel I found others are much better from cost and quality wise... There are many sites which provide much better product compared to this. I recently bought solar panel based on that positive review given from here https://magesolar.com/best-rv-solar-panels-reviews/ and I found this product much better and its worth paying for this... While I was trying to find right product I came across many sites which has pretty good rating such as https://www.walmart.com/c/kp/solar-panel-controllers, http://www.sears.com/magnum-energy-solar-cell-charge-controller-pt-100/p-A011595045
 
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