Do We Need More Solar? Help Needed (1 Viewer)

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Sep 16, 2013
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Hey all.

We use around 1300w of power per 24 hours in our van. We currently have 4 x 100w panels on the roof, but because the van blew up before giving them a good test, and it's parked in the shade, we have no idea if they will produce anywhere near enough power.

Now about to fit out a new van and want to get this right.

Our options are:
1. Keep the 4 x 100w panels and hope
2. Replace with 3 x 250w panels (cost of £680 inc. controllers - would get some back on existing panels)
3. Replace with 3 x 250w panels and have the ability to angle them (cost - a lot :))

I was planning on going with option 3, but I'm having second thoughts. We like to wildcamp and I think having huge panels sticking 1m above the van (panels take up 3m x 1.5m) will be too intrusive to others. Also, in the winter, when most useful, the wind is likely to be higher. I don't think we would use the angling much.

Option 1 could be a huge mistake - not the easiest of things to change at a later date, so I'm nervous about this.

So I'm leaning towards option 2. 750w should keep us nicely topped up for most of the year. I think?

Before I decide I'd really like a few opinions.

How much solar do you have and how much power do you get from it throughout the year?

If you were using 1300w per day, what would you want on the roof?

Would you bother with angling an array this big?

Storage wise we have 400Ah of LiFePO4 and can survive 3 days with zero charging. We can also charge at a true 60A whilst driving and have EHU if needed. If travelling in winter we have no problem mixing sites and wilding.

Would really appreciate a few opinion here o_O

Cheers, David
 
Sep 24, 2013
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Have you got space for 3 250W panels. They would be full size domestic units. They are big and heavy.
 
OP
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Wissel
Sep 16, 2013
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Have you got space for 3 250W panels. They would be full size domestic units. They are big and heavy.

Yes. Just :D

The panels I'm looking at are only 1480mm in length, so will fit with my awning without any overhang to the side. They are 993mm wide, so 3 take up just under 3m. That leaves me about 70cm at the back, which is enough for my MaxxFan.

Weight wise, they are 16.5Kg each, so 49.5Kg total.

These are the panels if interested:
https://www.bimblesolar.com/solar/large-panels/250w-perlite-54cell-small
 
Sep 24, 2013
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Seems prices have dropped a lot since I fitted mine. I paid that for 130W panel four years ago!
 

Abacist

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Oct 15, 2013
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1300 watts = 108.33 amps at 12 volts so just over 25% of your battery capacity per night. 400 watts of solar is the normal yardstick for your size of battery bank. It sounds like you have a large B2B charger and you are happy to use a hookup. Apart from low sun in the winter I would have thought that your existing panels would be adequate and even bigger panels won't achieve more in the winter. Even if angled there is not much blue sky in winter and the days are short. Maybe spending the money on another battery might be the way to go. Do you stay in one place a lot or do you move around in which case the B2B will pay dividends?

Not very scientific but those are my feelings.

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Apr 27, 2016
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Here's another way to look at it. As @Abacist says, 1300 watt-hours is 108 amp-hours. In good sunlight, 400 watts of panel will produce about 24 amps. So you would need 108/24 = 4.5 hours of good sunshine to make up your daily power use.

750 watts of panel will produce about 45 amps, so you would need 108/45 = 2.4 hours of good sunshine with these panels.

The choice is yours, but for comparison even a 4000 watt array on an angled house roof won't produce 1300 watt-hours on some winter days.
 
Apr 27, 2008
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I have 4x100w panels. Yes 24amps in very good summer sunshine but nearer 10-15amp in whats usually available With b2b and not objecting to the odd site I would think your present setup is enough..
 

Lenny HB

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Oct 18, 2007
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Whatever you do will not produce enough power on a winter's day. In January on a bright sunny day a 100w panel will only give about 2 amps for a couple of hour around midday & angled over 50% more.
Which ever option you choose won't give enough power to be completely independent.

As you don't mind using site occasionally how about a compromise.

a) Keep the exsisting 4 X 100 w panels and fit angling.
b) 4 x 150w panels with angling.
 
Aug 6, 2013
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Meaningful angling arrangements are very difficult and clumsy to arrange - more so if the van can't be ideally positioned. 250W panels are cheap compared with multiple smaller ones and, given the room, easier to mount. My experience recently (last week) is that on a bright but totally overcast day I see around 5A by 10am from a single 250W panel. I think I might get another one :).
 
OP
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Wissel
Sep 16, 2013
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Horncastle, UK
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Thanks for the replies guys :)

I have 4x100w panels. Yes 24amps in very good summer sunshine but nearer 10-15amp in whats usually available With b2b and not objecting to the odd site I would think your present setup is enough..

10-15A is around what I'd guessed (from having 2 x 100w panels before and knowing the charging I got). I'd think it likely I'd get around 60-70A per day (over warmer months, on average) with 4 x 100w. That leaves me a deficit of around 40-50Ah.

Your right in that I could just drive for an hour and replace this (or use EHU), but one of the main reasons I went for LiFePO4 was to have more power and not have to constantly monitor usage.

If I got the same ratio of power with 750w I should be solar sufficient (again, in warmer months). Seems sensible as very little money compared to what the storage and charging cost?

Meaningful angling arrangements are very difficult and clumsy to arrange - more so if the van can't be ideally positioned. 250W panels are cheap compared with multiple smaller ones and, given the room, easier to mount. My experience recently (last week) is that on a bright but totally overcast day I see around 5A by 10am from a single 250W panel. I think I might get another one :).

Thanks for that. I've read quite a few times that people have had better results (in less sun) with larger, higher voltage panels.

I have another van here atm that I'm finishing for someone else. It has a higher voltage 295w panel and I've been astonished at the difference.

Still undecided on the best way forward o_O

Part of me thinks that fitting the most I can fit on the roof makes sense, as it would give me the greatest "chance" of replenishing my batteries for more of the year.

I think rigging up something strong enough to angle panels this big would be heavy and probably not the best idea.

So at this moment I'm thinking the 3 x 250w, and having to be on a site every third day in Winter. Maybe :D

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