Hopefully we will be picking up our first caravan in the next week or so. I would like to be more independent of EHU so am looking at perhaps fitting a solar panel on the roof to recharge the battery during the day. I was looking at a panel around 60-80W. As far as I understand the connections are panel > controller > battery.
My questions are:
How would the solar panel be secured to the roof? I presume drilling holes would introduce a potential leak source. Are there special brackets?. Adhesive?
Any recommendations as to type/make of controller that any of you use?
Just trying to tap into the collective wisdom on here.
------------- Phil
Blood, Sweat and Beers.
The more I learn the more I know, the more I know the more I forget, the more I forget the less I know
Booked so far:
June: Charity Farm
July: Gullivers MK
August: Tregurrian, Cornwall
Sept: New Forest
A solar panel flat to the roof will never be as efficient as one inclined and facing (or preferably tracking) the sun.
Your 60W panel may only be producing 30W and even less on a cloudy day.
Setting the solar panels on a stand facing the sun would be a better arrangement.
Whats up with EHU? Kettle, microwave, electric heaters etc will not work on battery
A roof mounted panel is compromised much more in the winter than in the summer, because the sun angle is low.
In the summer whilst it is not the optimum angle it is close enough not to be a compromise. It also means you can go out for the day without staying in to orientate it every hour or so if seeking that optimum.
I have an 85 Watt free standing one to seek every bit of power I can in winter, but it is often a losing battle. In the summer it has typically done its job by 11 in the morning. In summer I leave it flat on the ground, to minimise the hassle.
Panels now come in two popular forms, a rigid unit using tempered glass and framed in aluminium, and a semi flexible one for bonding directly down to the roof.
The rigid is very well proven technology, can be the cheaper, but is somewhat heavier[I think my 85 Watt is about 7 kgs]. The rigid are fixed to the van roof with brackets, either plastic or themselves aluminium and these are bonded to the roof with a polyurethane adhesive such as one of the Sikaflex range. Given you clean the roof properly a quality PU product will never let go. The panel is screwed to the mounting brackets with stainless steel self tapping screws and designed to be about half an inch off the roof to ventilate away heat. cooling solar cell helps in their performance.
You can get cable glands that can also be bonded with PU to the roof for water tight cable entry.
There are several types of controller and massive differences in quality and performance. MPPT maximum power point tracking give the greater off peak efficiency if twined with special high voltage panels as opposed to normal "12 volt" system panels. But MPPT controllers of quatity are very very expensive and at current prices for panels buying a few more "watts" to offset optimisation, is by far the cheaper option.
The most suitable type of controller is a PWM type [pulse width modulating]. These work correctly with the 17 to 20 volt solar cells typically sold for 12 volt charging system. Now you can buy cheap MPPT and PWM controllers but do so with great care as fakes and rubbish are out there. I recommend a Morningstar PWM controller pitched at £35 ish as the best buy.
Solar cells are offered with differing technology, but eiterh of the two crystalline types perform well for a given panel area. Mono crystalline can be slighly higher performing, but an 85 Watt panel is an 85 Watt panel, just a mono crystalline migh be 10% smaller but possible more expensive.
Wiring up is as you say, and is dead easy but place the controller in the same ambient as the battery as it will need to sense the battery temperature, and being close it can compensate for wiring "losses".
Searching on this and other forums should yield a lot more info; some of it can be trusted!
Swaggy - I must admit the thought of drilling a hole in the roof sends shivers through my body. I have an 80watt panel what are used on the roofs of houses. It came with a frame but had to make a pivoting leg to give the best angle for charging. The controller came with it and was bonded to the back of the panel. I was throwing my old electric mower away so I cut off the old cable and used the old in line plug and socket. While i was at it I replaced the standard battery clamps for quick release ones. I used a little of the mower cable and combined it with the caravan battery leads with the other end having the inline socket - when not in use this socket is pushed back into the battery compartment out of the way.
Someone has said to me that the cable is too long and should use specialist cable but I have used it for 2 years when needed on non hook up site and never had a problem. In fact it kept the battery topped up for a week in Blue anchor bay in November this was with a lot of TV too. At sundown I always move the panel to the sunup position just in case I have a lie-in.
------------- A barman is just a pharmacist
with a limited inventory
Thank you for all the wonderful information so far. A couple of more points to those who have panels:
If its not fixed, what do you do with the panel when you are away from the van for the day? During daylight hours is when you want it working most. I thought about a roof mounted panel, although its slightly less efficient, because of the risk of it being nicked if it was anywhere lower.
If on EHU, where the battery is being charged normally, does the panel need to be disconnected from the controller or the controller from the battery.?
It would only be used to top up the battery when I'm on a CL site which doesn't have EHU. Is it just a matter of running a cable from the panel to the controller, or connecting the controller to the battery when needed?
Sorry about all the detail, but once I get it straight in my head then I'll be quite happy to go ahead and fit it.
------------- Phil
Blood, Sweat and Beers.
The more I learn the more I know, the more I know the more I forget, the more I forget the less I know
Booked so far:
June: Charity Farm
July: Gullivers MK
August: Tregurrian, Cornwall
Sept: New Forest
This should give you an insight to the requirements.
You don’t need to wire up or use the “load” feature as we have no need to “control” loads in our caravan application.
In the summer daytime placing the panel on the ground, tilted at 15 degrees to the ground and facing due south will optimise the yield for a panel that stays put, i.e. going out for the day mode. You will achieve more panel output potential by tracking the sun, but you can only “take” what the battery can absorb. So if the battery is full by 11:00hrs it matters not a jot thereafter.
Thus the logic of setting it to the best fixed position outlined above if you are not going to be on site to move it about. If you slept in and are going out in the afternoon and still need a power fix, set the panel a bit more to the west of south, where the sun is going to be during your absence.
Security: perhaps I have been lucky over the last nine years. I just use a braided cable like this linking a wheel spoke to a padlock through the panel’s aluminium frame.
A quality solar controller can be left connected to the battery. I use a plug and socket on the cable from the panel to the controller. My controller is mounted where it should be just on the other side of my battery housing, sharing similar temperatures for voltage correction, and compensating for cable run losses.
It is immune to whether I am on EHU or even if the panel is or is not connected.
In use, shadows really kill a panel's output, way out of proportion to amount of area in shadow. So think trees, van's shadow and very important grass blade shadows; place base on an old ground sheet to keep grass blades out of the way; don't as so often seen plonk a cell with its base down in the grass! Wash it regularly.
Additionally, for security when not in use and for storage my rather large 85Watt panel lives in a locked plywood box mounted to the rear underfloor of the van. Accessed from behind the van, sliding the panel on plastic angle guides, with the box [cassette], mounted within the Al-Ko chassis girders. All covered to be free of dirt etc.
This avoids manhandling a hard cornered panel though the van past the furniture, or trying to house it protected in the car. It also avoids having to make and get the panel in and out of a carrier tote bag.
To facilitate siding it in a box that is only the panels thickness, its homemade hinged easel frame folds down within the panel.
I do actually use my EHU cables as the main run from panel to the controller. They have oodles of copper to carry the current with near zero voltage drops, the negative line even sharing both the EHU leads neutral and earth cores. I carry the two EHU cables a long and short one anyway. This potential for a long lead facilitates chasing the winter sun where shadows are trying to cheat me of power.
i have a 160 watt on my roof of my caravan bonded to the roof only hole drilled in roof was for the cables.. this time of the year it will charge the battery up over a day in summer cant comment yet as only had it up there for 4 weeks...I am on a permanant site for a few months but i use the 12volt lighting a lot as they are on dimmers..I do steam rallys in the summer so the panal was mainly bought for non ehu as well
------------- lunar solar ecclipse 4 berth. living in caravan permantly on site.
I agree with posts relating to the inefficiency of roof mounting the panel (JTQU has provided excellent and thorough advice too), however from a view of both security and convenience I had my 120w panel roof mounted, ran by a decent MTTP controller (I had a remote display too to monitor operation). As mentioned, the frame was bonded to the roof and a single entry hole under a well sealed gland served the purpose. The 120w performed exceedingly well during the summer and ran more than adequately over the winter months too. We aren't heavy demand users, but as year round rally folk, this set-up served our purpose well.
We now have a different van with a daft 40w panel factory fitted, however I shall be upgrading this soon by some means, to replicate the type of set-up I describe above.
Roof fitting of the panel was straightforward enough, but if you follow this route, then give the installation some thought for practicality of running cables, placement of controller etc. I installed the controller at the bottom of the wardrobe, but behind the battery locker for close positioning to the battery. Some neat self adhesive mini trunking concealed all cabling and once fitted, I simply just left the panel to it. No need to disconnect or switch for when on EHU, and I was confident of being able to hitch and go without concern of the state of the battery charge.
Basically the same as G7ACU. We have a 135w panel on the roof and it seems to cope well. We have just come back from a 4 day new year rally and the battery lasted. There is no doubt a free standing panel can be more efficient but a roof mounted panel is fit and forget which suits us.
I would get the largest panel you can afford get a decent controller. I am not convinced that a MPPT controller with a single panel gives that much more performance.
What I wouldn't do is to neglect the battery. You can generate all the electricity you like but if you can't store it then it is a waste of money. I would also change your lighting to led as this makes a big difference to the amount of electricity that you use.
Mounting the panel on the roof would be a no no as Elddis will not honour the guarantee. I too was very apprehensive before I bought a panel and at the time asked people lots of questions which I never had an encouraging reply. I saw a buy it now panel with the controller mounted to the rear of the panel. This is the best solution as the cable runs straight to the battery without having to wire up in the caravan. If I am going to a site with hook up I leave the panel at home. If not the panel travels in the van I secure it using those adjustable camlock straps. The strap is fed through gas drop holes on the seat panel and holds it in an upright position with out bouncing about. As for security I use a bike lock (3mtr) and loop it through one of the legs and lock to panel.
This is the simplest and cheapest solution and can be transferred to your next van with little fuss.
------------- A barman is just a pharmacist
with a limited inventory
Amazing family weekend with old steam engines, classic car displays, market stalls, and full catering and bar. And camping on site - Save £25 by booking in advance.
Topic: Solar help!
