Hello All.
We are thinking of buying a couple of small solar panel to trickle charge our caravan battery when we are not there. And the other one on our car as it is " laid up " for days on end. What are the pros and cons please ..thank you.
------------- A war does not decide who is right , just who is left..
After various setups with solar panels, my take on them is this:
The small panels are useless, because they don't generate enough power, consistently, if the weather is cloudy or raining, it can reduce the output by 50%.
I use 3 60W panels, which in full sun produce about 9 Amp, this in turn more than keeps our 110 Amp battery topped up, even when cloudy.
At present our caravan is parked on the drive, 2 of the panels are just laid on the garage roof, and the cable connected to the caravan battery, as yet keeping it fully charged. But because of short day light hours, I will have to keep checking the battery. I think it should be ok over winter.
It sounds as though you are talking about a portable type, which raises the question of where will you site it? If portable it will have to be in van in which case there are likely to be periods of the day when it gets no light at all.
Its certainly a good idea to go solar, as the van battery is always kept fully charged and ready to go. If you can stretch to it get one mounted on the roof - its more efficient and (dis)connecting is another job less to do/forget
Oh, and they do work in winter. I put a datalogger on my battery, and found little change in voltage, except for a small drop overnight
Thank you guys.... yes I am on about a small " suitcase" type panel... I only want it to keep the caravan topped up while in storage, and for the car , again just topped up , because we don't use the car every day , and for some reason the battery drains quickly. ( this only happened last winter , and not th3 summer, and last week when the it got colder , you could hear the car " struggle " a bit
------------- A war does not decide who is right , just who is left..
Would be good if the van faced South through the front window. You could put it on the window cill or table or a box or a work mate whatever. It would get a fair bit of sun during the day.
Probably about 20 watts like that would keep it trickle charged if it was already charged.
We have a 100 watt on the roof and it recharges really quickly if I put a few lights on in the depths of winter.
I fitted a battery isolator switch from a boat suppliers, it is designed for two batteries 1, 2, both and off. On my caravan it selects Van, Mover, Both and Off.
In the off position the battery is completely disconnected and held it's charge (plenty for the motor mover) from November to Easter
Wintertime use of solar panels even simply for keeping a battery well charged can be very challenging and cannot be assured with small panels.
Issues faced are some van's have quite parasitic inherent drains from controllers, alarms and trackers; without these a decent battery would hold a charge for at least two months needing no support. A poor solar system can actually add more drain to power it than it contributes in winter.
During winter the sun angle is very low so shadows become a big issue, plus even small areas of shadow decimate a panels yield. Here also grime, leaves,bird droppings etc can have the same very damaging effects.
Placing the panel flat, IE horizontal leaves it far from optimally aligned to any available direct light, its yield reduced to reflected light from the clouds.
Winter tends to bring few really bright days, and of course the light hours are themselves much reduced.
All this combines as said to make solar much more difficult in winter and to increase its viability one needs to go over the top on what might be otherwise assumed.
I would suggest to even be hopeful of "getting away" with not risking the battery going too flat we have to be looking at a 40 odd Watt panel, and one that is well placed. Otherwise, it is more just by chance it might help rather than designing to give the best hope.
Select a site where the longest period of direct sun falls, it will be facing south and clear of most shadow tracks. Place the panel at about 45 degrees or more vertical rather than horizontal as this improves both alignment and self cleaning. Ensure it is far enough off the ground not to have any part shaded by weeds grass etc.
With the price of panels being now so much cheaper than they were I suggest really going over the top in sizing, with a decent controller you can't over do it. Important is buying a decent solar controller as these sap power 24 X 7 from the battery to power them and I know some poor quality ones take very much more power that others of better quality; I have measured one that proved to be the biggest storage drain on the battery and way more than his modest panel put back.
Quote: Originally posted by Carrievan69 on 14/11/2017
JTQU.
I would keep it indoors against the window.
You would IMO be wasting your money. If it yields enough with the challenges that inevitably places on it then the battery drain must be low enough not to need it.
Being behind a window will lead to a lot of shadow issues unless you keep turning the van to track the light, and the degradation to the light energy passing though plastic moulded windows is sevre.
If it is a very old van with flat glass windows things would not be quite as bad.
With a decent panel of 100w flat on the roof, winter is simply not an issue.
I wouldn't bother with a small unit either - I think you will be disappointed with the performance, for the reasons JTQU states. You'll finish up spending again to achieve your aim. Remember small units may have unregulated output too, which is not good in an unsupervised set up.
Caravan makers kicked off with 20w units, moving to 40w, then 80w and now 100w.
The solar type of panels I have fold up, like a book and fit in the boot of my car. They are fitted with a stand & regulator. Once I get to where ever I am going , I take it out, unfold it, face it into the sun, couple it to the battery [ crock clips]. The other panel, I slide that onto the caravan roof, this one is hard wired with separate regulator, into the same battery. This solar I carry inside the caravan, they work a treat, produce enough power, for all my requirements, tv satellite, etc.
As mentioned before, I have put the double solar onto the garage roof, to get more use out of the panels, rather than a few weeks a year, when we are in the caravan, where many times we are not on electric. hope this clarifies things.
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Topic: Solar panel.
