solar panel

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Jack B

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Hi,
I was wondering how much charge you would get from a advertised 10 w solar panel, do they actually produce 10w. I only need to charge a smart phone and have two led lights onboard, so I don't need that much power.
Thanks Jack
 
You wont get the theoretical maximum from the panel even when on a good day. I've got 2 x 80 watt mono panels and the maximum current i've managed is just over 8 amp at 12 volt, therefore 96 watts out of a theoretical 160 watts. Thats in the Med so expect less in sunny England. If you have the space i would go for at least 80 watt. I've just bought a third for this year for £74 off ebay.
 
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John_d_Smith said:
You wont get the theoretical maximum from the panel even when on a good day. I've got 2 x 80 watt mono panels and the maximum current i've managed is just over 8 amp at 12 volt, therefore 96 watts out of a theoretical 160 watts. Thats in the Med so expect less in sunny England. If you have the space i would go for at least 80 watt. I've just bought a third for this year for £74 off ebay.
Click to expand...
80w is much too big for the OPs needs but it depends on the size of your battery. If he's got a 100 ahr or less, and only the power reqs he describes, 20w would be my recommendation - with a simple regulator.
 
Jack B said:
Hi,
I was wondering how much charge you would get from a advertised 10 w solar panel, do they actually produce 10w. I only need to charge a smart phone and have two led lights onboard, so I don't need that much power.
Thanks Jack
Click to expand...

No you won't get 10 watts. That is the theoretical maximum and will be at terminal volts somewhere in the range 15 to 17 volts depending upon the panel


Presumably the solar panel will be charging a 12volt battery that will be powering your lights and other gadgets .. A small leisure battery or similar?

I use a 5 watt Specralite ( semiflexible) solar panel to keep my 60Ah leisure battery charged ........ my lights are mostly filament types .. I have a VHF RT and an Autohelm auto pilot.

The 5 watt panel is adequate for my needs. Weekends and occasionally up to a week.
 
It depends on the size of the battery. If you are charging something between, say, 75 to 100AH then a controller is not essential with a 10W panel.
If the battery is much smaller then a controller would be advisable to prevent overcharging the battery.
 
Jack B said:
Thank you for the replies.
I think I will go for a 10w panel http://www.sunstore.co.uk/12v-10w-Monocrystalline-Solar-Panel.html, what else would I need, is one of these
necessary http://www.sunstore.co.uk/EP-Solar-Landstar-5A-12V-Solar-Charge-Controller-60w.html , my budget is very SMALL so I have no money to waste on an overkill.
Thank you as ever,
Jack
Click to expand...

The common rule of thumb is that if you do not exceed the ratio of 10watts of solar power to 100Ah of battery capacity you do not need a controller although one is recommended for solar panels larger than 10watts regardless. Therefore if your battery is around 100Ah or larger you do not need a controller with a 10watt panel.
 
VicS said:
The common rule of thumb is that if you do not exceed the ratio of 10watts of solar power to 100Ah of battery capacity you do not need a controller although one is recommended for solar panels larger than 10watts regardless. Therefore if your battery is around 100Ah or larger you do not need a controller with a 10watt panel.
Click to expand...

Unless your panel tracks the sun you are never likely to get 100% output for a sufficient period to raise charging voltage above 14.2v, which is when battery damage occurs, making 10% a conservative limit. I have used a 10w panel unregulated on a 70Ah battery for the last year without ill effects.

ghostlymoron said:
80w is much too big for the OPs needs but it depends on the size of your battery. If he's got a 100 ahr or less, and only the power reqs he describes, 20w would be my recommendation - with a simple regulator.
Click to expand...
I would agree that 20W is the ideal size. I took a 10W panel on a kayaking trip to charge phone and vhf and even in bright sunlight it struggled and never brought the devices up to full charge..
 
The OP has said he just wants to power two LED's and one mobile phone. He also wants to keep costs down, so talk of 100AH batteries, controllers and 20 watt panels is all a bit OTT. If his two LED's use 1 amp and he uses them for four hours a night they will only be using 4AH's.

Odds are that he could get by with a much smaller battery...20 or 30AH maybe and a smaller panel? But he really needs to say just how he will be using it. Is it just for the odd weekend? How much power do his LED's use and how long will they be on....a couple of hours on a summer evening, or several hours when the nights draw in?

It may even be possible to just get a battery and take it home for recharging when he leaves the boat. No panel, no controller needed.
 
ukmctc said:
it'll just top up the batteries and no more, but will probably do ok for what you want.
Click to expand...

What else do you want it to do?
Incidentally, I think its worth having a simple regulator regardless of whether its necessary as it gives you useful indication of the battery state and whether the panel is actively charging.
 
pbo did an article on solar panels in 2011, issue 537.
I got a wee bit bored and did not read all of it, but it may do you a turn = they do a copy shop of course or you can have my copy for free.
 
gadget user said:
pbo did an article on solar panels in 2011, issue 537.
I got a wee bit bored and did not read all of it, but it may do you a turn = they do a copy shop of course or you can have my copy for free.
Click to expand...
things have changed quite a lot since 2011, prices have come down dramatically and more efficient controllers have come on the market for about ten quid. Have a look at Sunstore.
 
ghostlymoron said:
What else do you want it to do?
Incidentally, I think its worth having a simple regulator regardless of whether its necessary as it gives you useful indication of the battery state and whether the panel is actively charging.
Click to expand...

I disagree about fitting a controller. A controller by nature delivers 14v to the battery terminals. If the battery is near fully charged then charge current will be limited. A panel alone will keep charging as hard as it can right up to and beyond fully charged. If the current is small that doesn't hurt the battery. Fit an amp meter by all means to check operation of the panel. olewill
 
William_H said:
I disagree about fitting a controller. A controller by nature delivers 14v to the battery terminals. If the battery is near fully charged then charge current will be limited. A panel alone will keep charging as hard as it can right up to and beyond fully charged. If the current is small that doesn't hurt the battery. Fit an amp meter by all means to check operation of the panel. olewill
Click to expand...
I didn't know that the regulator limited the charge voltage. I thought they just switched on and off. Maybe an ammeter is a better bet.
 
Jack B said:
Hi,
I was wondering how much charge you would get from a advertised 10 w solar panel, do they actually produce 10w. I only need to charge a smart phone and have two led lights onboard, so I don't need that much power.
Thanks Jack
Click to expand...

Sod all. I have a 35 watt panel and the best I have ever seen from it at mid day is 2 amps ie maybe 25 watts. Dont forget that depends on daylight and your phone battery can run flat at night. Plus you only need lights at night. You havent mentioned whether you have a boat battery at all and if you have, then batterries lose charge just sitting there and will take up part of the output just to keep at 12.7 v.
 
ghostlymoron said:
I didn't know that the regulator limited the charge voltage. I thought they just switched on and off. Maybe an ammeter is a better bet.
Click to expand...

They work in different ways
The very simple ones just disconnect the panel from the battery when the volts have reached predetermined value, and reconnect when they fall to another'

Pulse width modulation , PWM, types break the charge into decreasing length pulses as the battery becomes fully charged.

The rule of thumb in post #8 will enable you to decide if a controller is needed or not.

Fit an ammeter if you really want to know the charging current.
 
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VicS said:
They work in different ways
The very simple ones just disconnect the panel from the battery when the volts have reached predetermined value, and reconnect when they fall to another'

Pulse width modulation , PWM, types break the charge into decreasing length pulses as the battery becomes fully charged.

The rule of thumb in post #8 will enable you to decide if a controller is needed or not.


Fit an ammeter if you really want to know the charging current.
Click to expand...
My regulator has 2 LEDs. One (amber) shows whether the panel is charging and the other (green) shows if the battery is fully charged. It's re-assuring to get to the boat and see the green light on. I'm not really interested to monitor the actual current.
 
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