What size solar panel? (1 Viewer)

[Dorwyn]

I have a new well equipped PVC and wish to add a solar panel. My previous vans were also PVCs but had compressor fridges, so I had as much power as I could reasonably fit on the roof. In this van I've spent a max of a week off leccy, but needed to run the engine after a few days, though that didn't work too well. There's a 3-way fridge, 2 way Truma for heating and hot water, possibly a 12v TV, but not much else that draws power, no inverter for example. 110 amp LB.

I'm hoping a 150 watt would be sufficient, or even less. Advice?

Also, how good are the roof wind deflectors in practice. I'm looking at a larger full width Fiamma, having had an expensive bird strike on my front Heki Midi. I thought it might protect that in future, and also cut down on wind noise and drag.

 

[pappajohn]

Fridge...no problem, it only works on 12v with the engine running.
Heating/hot water on gas if no 230v available.
12v tv uses very little.....3 or 4 amp hours at most.

A 150w panel will easily keep on top of your usage and will charge the battery faster than an 80w or 100w if the sun is weak or intermitant

 

[tonyidle]

I agree with pj BUT - you cannot have a panel that is too big. If it'll fit on the roof and you can afford to buy it bigger is always better. Again, as pj suggests, mainly for the dull days.

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[MitchandJenny]

We only have 100watts on the roof and one 110AH battery. We have been off grid for 3 months and no prob's BUT that was Summer..
I would think that two batteries will do you better than a massive panel, but only my opinion..
Mitch.

 

[Jaws]

As said, the more solar energy harvested the better.. Remember, not all conditions are conducive to decent charging from a panel
We have 300w of panels ( 3 x 100 ) which will put a few amps in even in poor weather conditions

 

[Minxy]

We have two 95AH batteries and a single 60w semi-flexible solar panel and having done 2 x 45 day holidays this year (9 May to 18 June and 6 Sept to 20 Oct) we didn't have any issues at all with low power - we only wild camp or use aires and never have hookup.

I'd suggest doubling your battery capacity and getting a large single panel or, my preference, 2 smaller ones - this may cost more but if one suddenly develops a fault you can easily disconnect it and still have some solar input from the other.

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[MitchandJenny]

I made a cock up when I said we had one battery !!
We have TWO 110AH batteries..
A red wine moment
Sorry.
Mitch.

 

[carolyn]

We have a PVC and a single 140a battery, we have a 120w solar panel from@eddievanbitz and have done a week with no hookup but it was sunny. 4 days in dull weather and the battery only dropped 2 bars at night watching tv and was back up to max by about 10am.

 

[MikeD]

We have a PVC and a single 140a battery, we have a 120w solar panel from@eddievanbitz and have done a week with no hookup but it was sunny. 4 days in dull weather and the battery only dropped 2 bars at night watching tv and was back up to max by about 10am.

We have a 140a battery but only a 100w solar panel and when it was sunny it also kept us constantly with enough power.
We parked on a site with a sun shade above (Spain) and again lasted around 4/5 days.

We are not heavy users of power though. All our lighting are LED's, we had no heating on and rarely watch the TV.

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[DanielFord]

We have 150w on the roof, and very similar power requirements to yourself (although we also have an inverter).
Our TV draws about 1amp, the blown air system seems to only add between 0.5 and 1 amp depending on how hard it blows!
Even over the last few weeks of very little sun, our batteries have been completely charged all the time.

 

[Sidney]

Our TV draws about 1amp

That's 12 watts. Is that a 6" TV?

 

[Bobby22]

That's 12 watts. Is that a 6" TV?

Modern 12v tvs use very little. We have a 21" and is uses around 1.5 amps/ hr

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[MikeD]

Modern 12v tvs use very little. We have a 21" and is uses around 1.5 amps/ hr

A shot from the Avtex site

View media item 21116

 

[Dorwyn]

We only have 100watts on the roof and one 110AH battery. We have been off grid for 3 months and no prob's BUT that was Summer..
I would think that two batteries will do you better than a massive panel, but only my opinion..
Mitch.

My last van was smaller but had more storage space, so we had 2x110 batteries, with 200 watt solars. Unfortunately since this new van was designed by someone else (Trigano) it does not have space for another LB, otherwise I would agree with you about more battery storage. But perhaps a larger panel would give a little more input in low light conditions. And it's not much dearer than a 100 watt. Thanks for the err .. input!!

 

[Lenny HB]

You don't say where and what time of year you are using the van which will effect the amout of solar you need. With a 150w panel and only one battery I would have thought you were pushing your luck outside of the main summer months. Bigger panels won't give you much gain unless you have somewhere to store the energy, you can't rely on very day being sunny. You say difficulte to fit another battery in, what about Gel batterys they give higher power for given size as you can discharge to 80% without much impact on life and they can be mounted any way up.

As you have a new van the last thing you want to do is run the engine to charge the batteries, leaving a modern engine on tickover is a good way of wrecking the the CAT & DPF.

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[MitchandJenny]

Watts equal Amps times Volts..
So Watts over Volts equal Amps.. So 23 watts over 12Volts equals 2 Amps...
Mitch.

 

[two]

Look at it as if your battery is a barrel. The bigger it is, the more you can store in it but it’s like a barrel with a tap only part way down the side: you cannot empty it completely and should expect to realise only half its capacity at best.

You need to replenish what you use as soon as you can and that can be done by a number of ways. Solar is one of them but it’s slow and uncertain. The bigger the panel system the quick it’ll do the job but, once ‘full’, you’re wasting any excess. Maybe waste does not matter, as solar is free, but you may not catch enough in poor conditions (Winter, bad weather, shade) to replace what you’ve taken out. The size of a solar system will depend on your usage, time of year, and how long you remain stationary.

Batteries are heavy, so avoid lugging any more around with you than you really need. You only need enough capacity to provide the electricity you’re likely to use before the next opportunity to replenish it (plus a contingency).

Solar is least effective at topping up in Winter, and the cold can also reduce your battery capacity, so everything is against you if ‘off-grid’ at a time of year when demand is also higher. In Summer your drain may be so slight that you won’t need to top up for several days and solar could be unnecessary.

I’ve enjoyed solar for many years but have not got round to putting it on my new van as I have not yet found the need. Those who rave about the capabilities of their electrical systems may be trying to justify their expenditure without knowing what their needs are.

I’d get a battery monitor, first, and watch the state of my battery bank very carefully. You should get an idea of how many Ah you need under different circumstances and how much you can reasonably expect to take out altogether.

Understanding that should help to identify the best solution. A larger battery bank may suffice.

You cannot manage what you cannot measure, you may be trying to fix the wrong problem.

 

[Sidney]

and the 21" Avtex is 2.17 amps
Link Removed Still very low

The Finlux 12v 22" TV/DVD is 22 watts - lower still

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[MitchandJenny]

 

[Dorwyn]

I’d get a battery monitor, first, and watch the state of my battery bank very carefully. You should get an idea of how many Ah you need under different circumstances and how much you can reasonably expect to take out altogether.

Understanding that should help to identify the best solution. A larger battery bank may suffice.

You cannot manage what you cannot measure, you may be trying to fix the wrong problem.

Yyes, but in practice I have found the need for a solar panel, can't fit a larger battery in, so on reflection I'll just fit the largest panel I can ... it's cheap enough ... and see how it goes. As regards winter input, I was constantly surprised how good the winter charging rate was on the previous van set up, where I had the compressor fridge running almost constantly. Admittedly it knocked out the batteries in no time. But that's another set up.

 

[DanielFord]

That's 12 watts. Is that a 6" TV?

Rather than posting the A rated sticker from the back, no it is a Cello 12v, not big, I cannot remember the size, but it is widescreen format, and I think it is 17". The figure I quote is with TV off, I look at the battery monitor, and then switch it on, the 1 amp is the difference between the two readings.
The satellite receiver seems to use about 1.5amps but then it also powers a small hard drive unit for PVR functionality!

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