Portable solar panels?

[Stumbleweed]

Having struggled to keep my leisure battery charged over last winter when the low sun generated very lttle power from my 2 roof mounted panels, I was thinking of temporarily attaching a small panel to my south-facing roof ladder. Also considered attaching a small wind turbine in a similar way.
Vehicle is on a storage site, (drafty old airfield).

Anybody have experiece of either option?

 

[B-well]

Hello Would it not be a lot easier to take home the leisure battery and charge it weekly.

 

[Tombola]

Foldable ahs a few miles in it, but dont expect anything decent this time of year in UK.
WInd turbine, poor and noisy

 

[Stumbleweed]

Hello Would it not be a lot easier to take home the leisure battery and charge it weekly.
View attachment 554300

I did that last winter, leaving a tiny lead acid battery from my generator in its place as I didn't want to let the starting battery die, (had to replace that in spring 2019 as all the batteries went flat over winter). Van was on my driveway with ehu over winter 2019/20 so no problem then, but 2 of my 3 leisure batteries died about this time last year probably because they didn't recover from the first winter. They're Exide Equipment Gel 140Ah so not easy to lug around or find space to charge at home.

 

[cyberyacht]

A panel of sufficient size to make a difference will be a bit bulky and as stored on a remote site there is the security aspect. Turn your van round and put a solar panel inside against the windscreen. A modest sized 40-60w to supplement the existing array should keep your batteries ticking over provided there is no significant current draw. How much have you got on the roof? Can you add more? Forget wind turbine. Barely effective halfway up a yacht mast with no wind shadow at all.

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[Stumbleweed]

Foldable ahs a few miles in it, but dont expect anything decent this time of year in UK.
WInd turbine, poor and noisy

Thank you for the info.
I've got room for something like a 60W 680x530mm rigid panel attached to the upper section of the roof ladder which is inclined about 15deg from vertical and points almost due south where it's parked.
My existing panels manage a trickle charge of about 1A on cloudy winter days, but only for an hour or two around noon. I assume this is because the sun is so low in Dec/Jan.

 

[Richard n Ann]

Thank you for the info.
I've got room for something like a 60W 680x530mm rigid panel attached to the upper section of the roof ladder which is inclined about 15deg from vertical and points almost due south where it's parked.
My existing panels manage a trickle charge of about 1A on cloudy winter days, but only for an hour or two around noon. I assume this is because the sun is so low in Dec/Jan.

How big are your existing solar panels? I'd have thought they'd be big enough to maintain a fully charged leisure battery, we're not talking about charging it from a nights usage are we

Do you know what the quiescent drain is on the leisure battery? There's a chap on our site has a 500ma drain with everything off and has no idea where it's going you might have something similar.

 

[Stumbleweed]

A panel of sufficient size to make a difference will be a bit bulky and as stored on a remote site there is the security aspect. Turn your van round and put a solar panel inside against the windscreen. A modest sized 40-60w to supplement the existing array should keep your batteries ticking over provided there is no significant current draw. How much have you got on the roof? Can you add more? Forget wind turbine. Barely effective halfway up a yacht mast with no wind shadow at all.

That's an interesting suggestion, thank you.
Don't know the spec on my existing panels, they're about 1200x500mm at a guess and I've seen peak charge currents of around 7/8A from them as far as I remember, (Ive got accurate figures, but they're in the van). There's room for more but I don't see much potential benefit specifically in Dec/Jan.
Continuous current draw < 100mA to power the electronics, marginally less if I remove the toilet fuse to eliminate its LED's

 

[Richard n Ann]

What about fitting a big Isolator on the leisure battery and just leaving the solar controller connected. Also could you fit a hinge on the rear of the solar panel so it props up and faces south? This will increase the output massively and you could use the hinges on site too.

I made ours hinge..

 

[Stumbleweed]

Intersting idea, very neat. Think I'd have to pivot ours lengthwise for the storage site, high winds could be a problem. I also thought about some sort of reflector positioned at the end, but wind concerns and getting on the roof to do it put me off.

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[Stumbleweed]

Took the plunge - 50W solar panel/controller/cables bought from fleabay https://www.ebay.co.uk/itm/23172124...d=link&campid=5338547443&toolid=20001&mkevt=1
Fitted it today, (turned the van round and propped panel against the windscreen roller/shutter), as per cyberyacht's suggestion, (thanks again).
It's pointed about 10 deg. east of due south and tilted about 20 deg. from vertical so should work pretty well.
My 12V sockets are powered from the leisure battery, so I've connected the solar controller to a 12V plug and hey presto.
Bargain price controller doesn't indicate charge current, just battery voltage, (12.7V indicated vs 13.1 actual), but it looks promising. If it can charge the leisure battery a bit more the main CBE controller will then start charging the starting battery too. (It's around 12.8V and started the engine easily today).
Existing solar panels were also charging the leisure battery at between 0.4 & 1.8A while I was there, so hopefully the combination will be enough - we'll see.

 

[Stumbleweed]

Did some proper measurements on Sunday, (which was untypically sunny hereabouts).
Solar controller connected to the battery with panel disconnected current drain of 8mA to power controller, (spec < 10mA).
With the panel connected in my initial position, (horizontal at base of windscreen) charging at 0.24A
Tried manually positioning panel while watching meter - best reading 1.25A, but this involved having the panel on top of the dash, roughly 12" behind the windscreen roller blind. (I think the huge curved winscreen 'focuses' the sunlight in this area).
Best position inside the blind, blind closed 0.4A, (as pictures).
Tried holding panel outside the side window, (not really practical to hold still enough for a proper reading but typical value was about 0.3A).
This is a 50W panel, max current 2.78A (which would be 50W @ 18V)
Best reading 1.25A = 17.5W @ 14V
As shown 0.4A = 6W @ 13.5V.
For comparison, my 2 roof mounted panels gave a best reading of 4.6A during this period, (roughly 12:00 - 13:15).

I may not have realistic expectations, but find this disappointing. Debatable whether the nett charge effect in typical winter weather is enough to cover the constant 8mA power drain of the controller.

I've read that placing the panel behind glass will reduce power generated, but by how much is anyone's guess.

Think I'll try siting the panel outside, in a fixed position, clear of the shadow of the fence for a proper comparison.

 

[Richard n Ann]

Even a tiny bit of shade on the panel will drastically reduce output. When our kitchen extractor lid is lifted and the sun is low even a 100mm x 300mm shade patch reduces ours from 4 amps to 0.3.

The one in our car windscreen reduces by about 50% because of the windscreen.

 

[Lenny HB]

Don't know the spec on my existing panels, they're about 1200x500mm at a guess and I've seen peak charge currents of around 7/8A

They are about 100 -120 watt 2 of them should easily keep your batteries charged over winter. In bright sunshine in June you should get around 15 amps. On our first van I only had a single 80 watt panel that kept the batteries charged without any problems.

Firstly I would check that both panels are working to make sure one hasn't failed or you have a wiring problem.
Then I would check for current drains that are flattening your batteries.

 

[Stumbleweed]

Thank you both.
I beleive both panels are working, (but will recheck if I can get access) and have produced at least 11A in sunnier climes.
Exhaustively checked all possible current drains over last winter, eventually concluding that leaving the CBE control panel on was a benefit as it enables starting battery to get charged occasionally, removed the fuse for anything else with measurable consumption down to the LED on the loo control panel

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[Stumbleweed]

Tested both original solar panels by simple expedient of draping an old towel over them in turn.
10:00 this sunny morning - 1.9/2.0A from both, 0.9/1.0A from either individually so I guess they're OK.
Not winning with preventing the leisure battery going flat.

 

[Raul]

Did some proper measurements on Sunday, (which was untypically sunny hereabouts).
Solar controller connected to the battery with panel disconnected current drain of 8mA to power controller, (spec < 10mA).
With the panel connected in my initial position, (horizontal at base of windscreen) charging at 0.24A
Tried manually positioning panel while watching meter - best reading 1.25A, but this involved having the panel on top of the dash, roughly 12" behind the windscreen roller blind. (I think the huge curved winscreen 'focuses' the sunlight in this area).
Best position inside the blind, blind closed 0.4A, (as pictures).
Tried holding panel outside the side window, (not really practical to hold still enough for a proper reading but typical value was about 0.3A).
This is a 50W panel, max current 2.78A (which would be 50W @ 18V)
Best reading 1.25A = 17.5W @ 14V
As shown 0.4A = 6W @ 13.5V.
For comparison, my 2 roof mounted panels gave a best reading of 4.6A during this period, (roughly 12:00 - 13:15).

I may not have realistic expectations, but find this disappointing. Debatable whether the nett charge effect in typical winter weather is enough to cover the constant 8mA power drain of the controller.

I've read that placing the panel behind glass will reduce power generated, but by how much is anyone's guess.

Think I'll try siting the panel outside, in a fixed position, clear of the shadow of the fence for a proper comparison.

Terrible placemat position for that panel in last photo, partial shade, and yes behind a window it will have a considerable reduced output. As the window and panel will not be perfectly parallel, a lot of little light available will be deflected and bounced of. The glass has iron content, not good for solar panel. Solar panels glass, is low iron and not flat, in order to absorb not bounce the light, when it’s not perpendicular.

 

[68c]

When I had a portable panel I used to open the skylight and lay it on the roof, then plug into the cigar lighter. The skylight closed OK as the wire is not very thick. Reasonably secure as is out of sight. I am not too clever but even I would notice the cable hanging down inside so never drove off with it on the roof

 

[Stumbleweed]

I agree placement is not great.
Putting it flat on the roof isn't going to work either.
I'm considering whether I could attach it to the various bars on top of the roof, propped at a suitable angle, say 19/20 degrees off vertical which should be best for Nov/Dec/Jan, (I have one approx 40mm dia. bar running along each side of the last 4m or so of the roof plus one along the rear edge / connecting with the ladder).