Solar Panels

Post by **powelly** » 03 Jul 2008, 11:52

I've noticed a few people on site with solar panels in the window when not on a hook up, do they actually do any good I realise they are not gonna power much but do they keep your leisure battery topped up enough to power the basics?

Ive been looking at Maplin and see that the big difference is the wattage but in real terms what does it really mean?

These are the ones Ive been looking at:

http://www.maplin.co.uk/module.aspx?Mod ... 58&doy=3m7

http://www.maplin.co.uk/module.aspx?Mod ... 60&doy=3m7

or maybe even mounting this on the roof!

http://www.maplin.co.uk/module.aspx?Mod ... 02&doy=3m7

Post by **Red Westie** » 03 Jul 2008, 15:35

The little panels just help between trips to keep the charge up in the battery, they are next to useless at actually providing real power but they are good all the same for the week/fourtnightly long periods where the van is just parked outside the house.
If you leave a battery flat and discharged the internal plates will become sulphated and so these panels are good at preventing that happening.
Unfortunately if you think one of these is going to put enough charge during the day to last the evening, then think again.
Even the large panels at 18watts are only equivelent to two strip lamps, forget about TV's , laptops etc... but a full day of rays should give the battery a good boost and prevent a flat battery at night.

Martin

Post by **AngeloEvs** » 03 Jul 2008, 18:12

What Solar Wattage rating means in basic easy speak:-

Divide 12 into the rated wattage of the panel you are interested in.

e.g 40W/12 = 3.3 The figure 3.3 is the maximum current the panel will generate so this becomes the max. Charge current at 12V.

Batterys are rated in Ampere hours so your 40W panel is capable of returning 3.3A per hour back into the battery.

However, this 3.3amps per hour depends on the following:-

1. The panel must face directly into the sun so that the light strikes it perpendicular to the plane of the panel.

2. It must be sunny with no haze or clouds.

3. the condition of the battery, (that it requires this charge because its capacity has been reduced, hence the need for a regulator otherwise you will overcharge the battery and damage it)

The solar panel will give less charge in dull or overcast conditions, or if the panel is not directly facing the sun.

Post by **phredd** » 25 Jul 2008, 19:23

Another question of Solar Panels:- >>>>
The attached pics are of a Panel I have been given:-
I would like to know the Amps I can expect from it.
I have had it on the Volt meter and had a reading of 24V in bright sunlight and about 12V at 7pm tonight with a slight haze in the sky.

The panel is 90cm x 30cm approx and has a label on the inside as shown.

[IMG:640:480]http://img167.imageshack.us/img167/3816 ... 003ge8.jpg[/img]
By phredd

[IMG:640:480]http://img246.imageshack.us/img246/2273 ... 001uw0.jpg[/img]
By phredd

I would like to use it for leasure battery top up.
Thanks for any info.
Phredd

Post by **Mocki** » 25 Jul 2008, 19:37

methinks it would be just the job Phredd.......

Post by **AngeloEvs** » 25 Jul 2008, 19:38

It's 14 W, if it doesn't have any dud cells then the max charge in bright sunlight will be around 1A/hr, good enough for topping upbut make sure it incorporates a blocking diode otherwise it will flatten the battery when the level of light falls. If it doesn't have the diode built in then you will need to get one or get a solar panel regulator from somhwere like Maplin, cheapy one is all you need.

Post by **VWCamperfan** » 25 Jul 2008, 20:58

You will also need a regulator as the output from that panel will fry the battery. Anything below 5 watts output can be constantly connected to the battery but anything above needs a regulator. Also the peak voltage output of that panel is too high for a 12 volt system so will need to be regulated.

Post by **AngeloEvs** » 25 Jul 2008, 21:21

It is the correct output for a 12V system. Typical off-load output should be around 24V, when connected to the battery it will fall to anywhere between 12V and 14V depending on light level and charge state of battery.

Post by **Red Westie** » 25 Jul 2008, 23:00

As a basic rule, the charge rate of a car battery should be around 1/10th of it's amp/hr rating, so that's 6.5 amps for a 65amp/hr battery.......so the 1.1 amp delivered from this 14watt panel is considered TRICKLE charge and will not damage the battery if left connected permanently. Besides, that's peak output when it is sunny and we know thats only 20-30% of the time. Plus the battery is rested during darkness. Trust me...your battery is under no threat from overcharging.
Martin

Post by **phredd** » 26 Jul 2008, 07:31

Hi Guys.

A big Thank you for all the input.
Now off to Maplins to purchase the item.

Have a low battery in the shed so I will see how it goes.

Phredd