Solar panel

[Rubix]

Does anyone have a suggestion where I could get a descent solar panel for replenishing the caravan battery.

I have seen a couple in Maplin both for a tenner, one is 1.5 W, the other is 2.4 W, the higher power one is out of stock in my local stores, but I was wondering what sort of spec are the average spec/cost ones.

Thanks in advance.

 

[rob_jax]

Rubix,

What do you want the solar panel to do?

Trickle charge an already fully charged battery to stop it discharging over the winter?

Or recharge a battery after you've been using it on the previous night for lights, music, water pump, whatever and you want a full battery when you return?

In the first case - internal battery losses can be up to 0.5AH per day - which means you'll need a total power output from the panel of around 10 watts. With maybe 5 hours of sun in the winter on a good day - that means the 2.4 watt panel is just about OK.

In the second case - replenishing use - then you need to add up your use - and buy a panel big enough. Think along the lines of a 40+ watt panel - during the summer that should pump 25AH back into the battery.

Robert

 

[staff]

Hi.

Look at this web site on solar for caravans and motorhomes

www.detriotsolar.com

 

[Rubix]

Thanks for your info Robert,

We only intend using it when we are on sites without EHU which for us will only be for weekends or when we go on rallies.

Our 'van only uses 12v for lights (all florry tubes, bar the bathroom light which is 2 filament bulbs), water pump, and I think ingition for the water heater (when running on gas). So this is obviously minimal usage.

We don't tour during winter so more power will be delivered in those sunny days we sometimes have

We store the 'van at home on our drive where we leave it connected to the mains to keep the battery charged.

I thought the 2.4 W one would be ample, and the 1.5 W might even work.

What do you think ?

 

[rob_jax]

Hi Rubix,

I'm guessing you'll have the lights on for 2 hours each night?

And it should be obvious how to adjust the maths to handle 1 or 3 hours in the following examples:

=== Night Use ===

One fluorescent light (10 watt rated) running for two hours will use: 10 watts x 2 hours = 20 watt hours (WA)

Multiply this by the number of lights working in the caravan - say three - that's a nightly use of 3 x 20 WA = 60 WA.

Plus the water pump (guessed to be equal to one lamp) and the ignition (minimal and can be ignored)

So that a total of 60 + 20 (water pump) 80 WA each night.

=== Day time replenishment ===

Let's hope for 8 hours of sunshine, during which the panel will supply it's rated output...

Divide the 80 WA by 8 hours - and that's 10 watts - so your panel will need to produce a minimum of 10 watts - and typical sizes will be 15 watts or 22 watts...

I'm afraid a 2.4 watt panel won't do anything for you. Indeed these low watt panels are just about OK to replace internal losses in the battery.

You need to do your own calculation following the example above...

Robert

 

[Ian341]

Hi Rubix,

we tried one of those solar panels that you mention, I think it was something like 2W and to be honest it was a complete waste.

On our boat we rely on solar panels when we are not in the marina, we have 2x20W panels. If you really want to notice a difference in the battery level then it is better to go for one of thise size. We have 4x 110ah batteries on the boat and it keeps them constantly full and even when we use a lot of power overnight it reachrges them quickly. On one occasion we managed to empty all these batteries by leaving the fridge on battery all night and after 3 hours of sunlight there was enough power to start the engine.

If we ever did go to a caravan site without electric i would definitely consider one of these, however, people we know do use a small panel and they use suction pads to fix it to the interior of the heki rooflight and a day of sunshine does increase the battery level a little.

Good luck with whatever decision you make.

Hope this helps

Ian

 

[Ian341]

Hi Rubix,

we tried one of those solar panels that you mention, I think it was something like 2W and to be honest it was a complete waste.

On our boat we rely on solar panels when we are not in the marina, we have 2x20W panels. If you really want to notice a difference in the battery level then it is better to go for one of thise size. We have 4x 110ah batteries on the boat and it keeps them constantly full and even when we use a lot of power overnight it reachrges them quickly. On one occasion we managed to empty all these batteries by leaving the fridge on battery all night and after 3 hours of sunlight there was enough power to start the engine.

If we ever did go to a caravan site without electric i would definitely consider one of these, however, people we know do use a small panel and they use suction pads to fix it to the interior of the heki rooflight and a day of sunshine does increase the battery level a little.

Good luck with whatever decision you make.

Hope this helps

Ian

 

[Rubix]

I wasn't sure what power the lights were, and as you have both said the small panels aren't really worth it so I will give them a miss.

Thanks for your help

 

[rob_jax]

Keep an eye out for special offers from Maplin, they've offered the higher rated panels at discount before...

Robert