Solar Panels tips

[Joemdt]

Hi friends,

Just bit the bullet and ordered a (100W monocrytalline) solar panel for our Bailey Phoenix 420. I was just wondering if I need a specific type of leisure battery to get the best out of it? Our caravan (and battery) was new this year, but I remember it saying "ideal for motor movers and minimal off grid use". It's at storage at the moment so I can't look what it is exactly at the moment.

Had anyone got any good advice?

Thanks again guys

 

[ProfJohnL]

Hello Joe,

There are many different types of batteries as I think you realise. from your description it sounds as though you may have got a battery which is similar to a cars starting battery. These are designed to give very high peak currents which makes the suited to starting cars, but this current usage will normally only last a few seconds as the car starts and the alternator sets about recharging the battery. These batteries like to be kept fully charged, and will be damaged if left part charged for long periods.

Their usage in a caravan and for a mover is fine provided the caravan is hooked up to the mains as soon as possible to keep it topped up.

It is deceptive to look at the power needed by a mover. It may have a peak start up current of about 80A, but its running current will be substantially less probably less than 50% of the peak current (it depends on the terrain) but even then if you work out how much battery capacity it uses to manoeuvre a caravan into position the drain on the battery capacity is surprisingly small typically less than 2Ah!

By comparison, if you use a TV or have the caravan lighting on for an hour it will use more battery capacity than the mover did. So its the small devices that are on for long periods that are generally the biggest users of battery capacity.

What this means is when of grid and relying on Solar Power to recharge the battery becasue solar power will only work during daylight hours it means the battery will be slowly discharged over longer periods. This does not suit car batteries and it can damage them. The leisure battery which is popular with caravanners is the way to go.

These are designed to withstand discharges and standing for modest times before being recharged.. They have a smaller peak current capability than a car battery, but they will be fine for use with a caravan mover.

Just as an aside, in the past we have looked at solar power, and many people find that 50W panel is enough to keep their caravans running almost indefinitely. Their are now more items that use 12V power so your choice of a 100W panel should be good. Go for at least a 110Ah leisure battery.

Do make sure you fit a solar panel charge regulator. This will prevent the panel from over charging the battery'

 

[LeMans]

We opted for 100w sargent solar panel with 100w A-class battery fitted to our 2019 Sprite Major 6 TD with Powrtouch Manual Evolution Mover.

The sales pitch was the 100A the Class A battery is designed for frequent use (off grid for example) and using a motor mover on a regular basis.

Not tried and tested yet, only had van over a month and there hasn't been much sun over Central Scotland in that time!

The basis for this choice was we attend Silverstone every couple of years with no electric hook up.

 

[Parksy]

Apart from the good advice with regard to the battery, the efficiency of the solar panel will depend on the solar controller, often called the regulator.
Pulse Width Modulation controllers (PWM or shunt controllers) are less expensive and less efficient.
MPPT (maximum power point tracking) regulators deliver optimum performance if the budget will allow.
Use led 12v interior light bulbs if not already fitted, cut down on power wastage and your 100 watt panel should easily cope off grid on reasonably bright days.
With the greatest respect to the Prof, I really wouldn't recommend a 50 watt solar panel for off grid general use in the UK.
We have an 80 watt monocrystalline roof mounted panel which struggles at times when we go off grid at music festivals and 1940s events
I'm considering upgrading to a 150 watt panel with a 115 amp hour leisure battery before next year.

 

[otherclive]

You should look for a grade B class battery as a minimum but depending on your usage style then a grade A class would be best particularly if you plan lengthy trips in winter.
Ensuring your light fittings have LED sources will help again in winter.

 

[ProfJohnL]

Apart from the good advice with regard to the battery, the efficiency of the solar panel will depend on the solar controller, often called the regulator.
Pulse Width Modulation controllers (PWM or shunt controllers) are less expensive and less efficient.
MPPT (maximum power point tracking) regulators deliver optimum performance if the budget will allow.
Use led 12v interior light bulbs if not already fitted, cut down on power wastage and your 100 watt panel should easily cope off grid on reasonably bright days.
With the greatest respect to the Prof, I really wouldn't recommend a 50 watt solar panel for off grid general use in the UK.
We have an 80 watt monocrystalline roof mounted panel which struggles at times when we go off grid at music festivals and 1940s events
I'm considering upgrading to a 150 watt panel with a 115 amp hour leisure battery before next year.

Thank you for the points about the type of charger controller.

With regards the size of panel, I am aware that the calculation we looked at was a few years ago now, and there were fewer 12V accessories of phones and tablets to be charged etc, which is why i said there are more items now and as such a 100W panel should be enough, but it all depends on what you try to use.

 

[Buckman]

We have an AGM battery and although it was flat at nearly 5v for a week, it recovered well. If you do opt for battery other than lead acid battery make sure that the controller has been set to that type of battery as lead acid and AGM have different charging regimes.

 

[Joemdt]

Thanks for the info guys. I've heard You can get an inverter so you can use 240V appliances. Is this a good idea? Will it just drain the battery really quickly? Or will the solar panel be able to keep up?

 

[Anseo]

Thanks for the info guys. I've heard You can get an inverter so you can use 240V appliances. Is this a good idea? Will it just drain the battery really quickly? Or will the solar panel be able to keep up?

There are ways of using an inverter without depleting your caravan battery (I'm still learning and taking advice from the good Sir Gafferbill )

In realistic terms, you will not maintain your caravan battery using solar power when the caravan battery is connected to an inverter (well perhaps, but only for the very shortest of durations of 230v use).

Another battery for use as a 'slave' I suggest would be a minimum requirement.

Keep working on it, I'm always interested in this kind of thing, if you care to share your findingsresultsoutcomes then that would be interesting for me to read.

P.S. The first bits arrived today for my planned DIY folding solar suitcase, looking forward to the other parts arriving, excited to see how it all works out

 

[ProfJohnL]

Thanks for the info guys. I've heard You can get an inverter so you can use 240V appliances. Is this a good idea? Will it just drain the battery really quickly? Or will the solar panel be able to keep up?

Hello Joe,

As Anseo has indicated you can use an inverter to produce 230V ac but it depends on what you want to try and run as to how long the battery would last and that is determined by the amount of charge in the battery and the power the combined 230V appliances need to operate.

To complicate matters further, there are basically two types of inverters the cheapest ones produce a stepped or modified sine wave output. These are the most efficient types of inverters and can run as high as 97% efficient, but the quality of their output is fine for pure resistive loads like heaters and filament bulbs but appliances with transformers or motors may object and not function properly and even over heat.

As a quick guide to inverters, what changes is the current from DC to AC, and the size of the current, and inversely the voltage will change roughly in teh ration of 230:12 or about 20x

So for example the fridge may use about 120W of mains power that equates to an 230V AC current of about 0.52A. Connect that to an inverter running from a 12V battery, and the same power is required (120W) but now we only have 12V so 120/12 = 10A at 12V dc In practice it will be more to offset the inefficacy of teh inverter as outlined above.

The upshot is its not practical to try and run mains appliances that require more than a few Watts of power through an inverter in a caravan. Generally speaking items like the fridge, and space and water heaters all have alternative fuels systems so they can use the gas, and of course boil water on the cooker hob.for drinks etc.

 

[Tukums]

Around 90% of our caravanning is off grid using C&CC meets and temporary holiday sites. I use a 150w folding panel which keeps my 110amp Numax battery charged up with no problem, so far for 15 nights. I often use a 12v TV for 3-4hrs a night and with the other caravan 12v systems the battery is normally charge back up by lunchtime in full sun or late afternoon if cloudy. Controller is on the back of the panel, IP66 waterproof, and I just connect up to the battery with a fused lead and Anderson plug, gives out 8amps in full sun and a boost charge if needed of 14.4v. I use a 150w inverter to charge up my 230v shaver and laptop; GPS watches, phones and bike lights are charged up with a USB adaptor (3 sockets) which plugs into the caravan 12v socket. Fridge, cooking, BBQ, hot water and heating if needed runs off gas, I have a Safefill refillable cylinder which I fill at my local Morrisons garage, 8.6kg/15ltrs costs £8.70.

 

[Scorpy]

I had a 100w Solar panel fitted as a150w I was going to have was to big physically and the dealer told me 100w would be quite adequate.
I have a 110w Leisure Battery and I run a Motormover, LED TV, Signal finder/booster, Lights, Shower, Phone chargers and the wifes Hair Straighteners all on 12 volt. I have fitted LED bulbs in place of Halogen throughout the van.
I can honestly say this is the best 'Must Have Accessory' that I have ever bought for the van/s in 35 years and regret not doing it years earlier.
I can run all these and even in dull weather the panel will keep the battery at 12v+ and on sunny days up to 13v+. Never gone flat on me since installation and very happy with it and we are off grid quite often at rallys etc. Wouldn't hesitate to recommend buying one, I bought mine on a Special Offer from my local Coachman dealer at £325 fitted and feel it was the best £325 I've spent on it.
Hope this helps
Mike

 

[Mandarin]

We just bought a 120w folding panel so we have the flexibility to go off grid if we want and are looking forward to testing it this summer, after a lot of research and advice we concluded this was a reasonable size as we don't tend to be frugal with power use. we also have a small 10w panel which we hang under the roof light to keep the battery topped up in storage, it typically sits at between 12.5 and 12.9v depending on the weather and nicely keeps up with the alarm useage - there's no controller but we were advised none was needed for such a small panel.

I'm planning to fit a permanently live, fused, power socket in the battery compartment to make it easy to plug in the panels.

The battery is a deep cycle leisure battery, suitable for repeated slow, deep discharge and high output for the Motor mover.

 

[otherclive]

We just bought a 120w folding panel so we have the flexibility to go off grid if we want and are looking forward to testing it this summer, after a lot of research and advice we concluded this was a reasonable size as we don't tend to be frugal with power use. we also have a small 10w panel which we hang under the roof light to keep the battery topped up in storage, it typically sits at between 12.5 and 12.9v depending on the weather and nicely keeps up with the alarm useage - there's no controller but we were advised none was needed for such a small panel.

I'm planning to fit a permanently live, fused, power socket in the battery compartment to make it easy to plug in the panels.

The battery is a measure battery, suitable for slow, deep discharge and high output for the Motor mover.

Do you just connect the 10w panel directly to the battery with clips?

 

[Mandarin]

For now yes, but its not ideal as there's not much room and its fiddly. For the future i will do this via the fused permanent live socket I plan to install. I would use one of the existing 12v sockets but of course they are disconnected when the master switch is off.

 

[BaileyNiggles]

Presumably foldable panels are the flat panel TVs and mobile phones of yester-decade, ie. fashionable, desirable, expensive, relatively rare and so pinchable. Yet surely the trick is to leave them 'running' as much as possible even when you're out and about?

How, out of interest, do retrofit rooftop ones work in terms of fixing, robustness, wiring-in? Am thinking preserving waterproofness of caravan shell, and not having it blow off and smash someone's windscreen whilst driving.

 

[otherclive]

There was an article in PC a while back on how a modern solar panel fits to a caravan roof. There is minimal screwed fixing the real bonding strength is by adhesive. From memory the only thing that penetrated the roof was the cable. Roof penetrations are commonplace viz rooflights up to 5-6, tv antenna etc so one relatively small cable isn’t a problem. Plenty of videos on YouTube including the ((vintage) PC one below.

https://www.youtube.com/watch?v=8WBAqT3FOCU

 

[Dodger524]

I stuck a 100w solar flexible panel straight onto the roof of our Lunar Clubman with Sikaflex so the only holes required were two adjacent 6mm cable holes both within the cable cover supplied with the panel.

It has now been in service about two years now and shows no sign of shifting, it is very much a fit and forget system apart from the occasional need to wash it.

I put a short article on my website about it for those that are interested.

 

[Guzzilazz]

I put panels on my boat in 2009, and removed and upgraded them in 2017. I used Sikaflex 291 to stick them both down, and when I removed the first lot was glad I hadn't really pushed them down, as I had to use a hacksaw blade to cut through the Sikaflex.

I made a mistake second time around, because I put the Sikaflex in a bead all around the panels... You shouldn't do this with higher power panels because there needs to be expansion room underneath to cope with the higher heat production. The recommendation is to use beads of Sikaflex across the panel. The current panels have a "sucked down" look, which may limit their life.

 

[Dodger524]

I put panels on my boat in 2009, and removed and upgraded them in 2017. I used Sikaflex 291 to stick them both down, and when I removed the first lot was glad I hadn't really pushed them down, as I had to use a hacksaw blade to cut through the Sikaflex.

I made a mistake second time around, because I put the Sikaflex in a bead all around the panels... You shouldn't do this with higher power panels because there needs to be expansion room underneath to cope with the higher heat production. The recommendation is to use beads of Sikaflex across the panel. The current panels have a "sucked down" look, which may limit their life.

You are right about the adhesive beading. The advice I followed was to apply a zig-zag of beading in order to leave a ventilation gap under the panel.