Maximum solar? (1 Viewer)

Feb 19, 2022
62
15
Anywhere
Funster No
86,982
MH
AUTO-TRAIL 740S
Exp
1985
Forgive the question; I am a complete ignoramus regarding anything electrical. I just don't grasp it.
So, a theoretical question.
Can you have too much solar, too many solar panels?
Panels are now relatively inexpensive.
 

Tombola

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Nov 21, 2020
4,165
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78,053
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Rapido
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Make sure your MPPT and cabling can handle the amount you have, plenty advice here if you let us know how much you are thinking of adding

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Nov 2, 2022
246
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Cumbria, UK
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Hobby Optima T65 de
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Too long
If you have a Hymer its usually the maximum capability of the electrobloc otherwise you are best connecting direct to your batteries I believe.
 

Swifter

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Jul 28, 2020
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As mentioned by Tombola , you will need a good match between your solar array input wattage and the capacity of your battery bank and obviously the correct MPPT configuration.
 
May 31, 2015
10,932
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Ducato PVC
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Getting Better
Always get as much up there that will fit and you can afford ā€¦.šŸ˜Ž

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BillWeb
Feb 19, 2022
62
15
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Funster No
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AUTO-TRAIL 740S
Exp
1985
Thanks everyone. I sort of expected terms like MPPT and electrobloc. Oh well!
But I am encouraged by the "more the better" responses. Given that, should you match them to even more than 2 linked leisure batteries?

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May 31, 2015
10,932
39,431
Cornwall
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Getting Better
Thanks everyone. I sort of expected terms like MPPT and electrobloc. Oh well!
But I am encouraged by the "more the better" responses. Given that, should you match them to even more than 2 linked leisure batteries?
No good having 600w of solar going into one 100amp battery especially in winter when heating tv charging and so soā€¦ in the shorter days.
Minimum 2 batteriesā€¦šŸ˜Ž
 
Apr 27, 2016
6,555
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Manchester
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42,762
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A class Hymer
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Since the 80s
So, a theoretical question.
Can you have too much solar, too many solar panels?
There is a limit to how fast you can charge a battery. One way of looking at it is to see what panel watts would give a maximum charge to a single battery.

A typical motorhome lead-acid leisure battery has a capacity of 100Ah (amp-hours). The rule of thumb is to limit the charging amps to a fifth of the capacity, ie 100/5 = 20A. In theory a 240W panel will produce 240/12 = 20A at 12 volts, but that's in tropical conditions. In reality, with a panel flat on the roof (not tilted) you'd need more like 300W of panel to give you 20A.

Often two or more batteries are fitted, especially if off-grid camping is what you want to do. Two batteries could take 600W of panel, and so on.

Lithium batteries are becoming more popular, especially for off-grid. The charging limit for lithium is much higher than for lead-acid, Many 100Ah lithium batteries can be charged at 100A. So in theory they could take the output of 1500W of solar panel. Good luck getting that lot on your roof!
 
Feb 27, 2011
14,300
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15,452
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Self Build
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Since 2005
If you are looking at lots of solar then consider LiFePO4 batteries as they can accept the charge faster and are far more efficient in their use of electric (you get more of it back out).
 
Jun 10, 2010
8,267
19,103
Shrewsbury (sometimes)
Funster No
12,013
MH
N&B Clou Liner MAN
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2006
If you are looking at lots of solar then consider LiFePO4 batteries as they can accept the charge faster and are far more efficient in their use of electric (you get more of it back out).
I agree totally and its a lot easier to change a battery than to start attaching panels to the roof, but would just add that if you re swapping totally to Lithium you need to check that your chargers have a lithium setting.

I've gone the hybrid route and now have one 220Ah Gel and one 200ah Life Po4, my aim being to up my usable capacity without changing my charging regime. Its early days yet as I havent had chance to use it for a long period but certainly looking promising.

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BillWeb
Feb 19, 2022
62
15
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AUTO-TRAIL 740S
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1985
So, match the number and/or types of batteries to the number and/or output of a given solar array?
If say on a cool bright summer's day the output exceeds the battery capacity, does the solar regulator adjust to suit this or other scenarios?
 
Dec 2, 2019
3,182
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Amersham
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67,145
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van conversion
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Since 2019
So, match the number and/or types of batteries to the number and/or output of a given solar array?
If say on a cool bright summer's day the output exceeds the battery capacity, does the solar regulator adjust to suit this or other scenarios?
Normal solar chargers will push in as much as the battery can take. Victron solar chargers you can set the charge amps limit in the settings.
An you can never ever have to much solar. Just wrong set up.
 
Apr 27, 2016
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A good solar controller has an intelligent charger built-in, and constantly monitors the batteries. Quite likely on a good sunny day, the batteries will be 100% full, so the controller reduces the charge to a float charge, practically zero. It controls the panel load so that no excess is generated. It's not like a house solar array, which always generates as much as it can, and sends the excess into the power grid.

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Mar 23, 2012
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sleights
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Forgive the question; I am a complete ignoramus regarding anything electrical. I just don't grasp it.
So, a theoretical question.
Can you have too much solar, too many solar panels?
Panels are now relatively inexpensive.
What do you have now and what doesn't it do that you want it too? That's your starting point. Then get whats needed plus a bit to spare.
 

Lunarfan

Free Member
Nov 21, 2022
5
2
Shropshire, UK
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92,562
MH
Lunar 620 SGL
Exp
Since 2010
When we did a lot of Wildcamping I fitted a Bosch 110amp Solar Panel on the roof connected to 2 batteries and it was perfect.
When the boss (better known as Jayne) decided campsites were better & safer we used EHU so did not need the Solar.
It's still 'up there' doing it's thing but the real answer is does your style of touring need a Solar or not.
 

RedFrame

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Sep 2, 2017
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I think Lunarfan raises a valid point.

If you will be staying in one location without EHU for long periods, typically 4 days plus then Solar is definitely worth looking at, however,

If you will be moving every couple of days, and or, want late Autumn to early Spring UK use then Lithium and B2B is likely a far more efficient, reliable and cost effective solution (this is of course depending on your alternator, what van do you have?)

Cheers
Red.

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BillWeb
Feb 19, 2022
62
15
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AUTO-TRAIL 740S
Exp
1985
What do you have now and what doesn't it do that you want it too? That's your starting point. Then get whats needed plus a bit to spare.
I'm looking for a potential change from coachbuilt to camper, something like a WildAx and days at a time off EHU. A camper roof (probably Ducato) along with roof vents, aerial, etc should allow just enough roof real estate for 3 or so panels.
Should I ask the dealer to arrange for the solar or take purchased van to a solar and battery specialist?
 
Mar 23, 2012
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I'm looking for a potential change from coachbuilt to camper, something like a WildAx and days at a time off EHU. A camper roof (probably Ducato) along with roof vents, aerial, etc should allow just enough roof real estate for 3 or so panels.
Should I ask the dealer to arrange for the solar or take purchased van to a solar and battery specialist?
You need to think what times of year you'll use it off grid and what your power requirements are. That will give you an idea of what size battery you need and what amount of solar to recharge. It's also going to be determined by whether you tend to move every day like us and so have some battery charging from the engine.
 
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BillWeb
Feb 19, 2022
62
15
Anywhere
Funster No
86,982
MH
AUTO-TRAIL 740S
Exp
1985
Will want to stay put for a week or more regularly.
Use? 12v TV, recharge phone, mifi, occasional inverter for laptop etc., winter lighting, ....

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RedFrame

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Sep 2, 2017
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In addition to Lenny's comment, I think you'll find you won't have enough "real estate" up top to service your requirements, other than in summer.

I'd go Lithium (at least 1Ɨ 300Ah) and 120A B2B, this will give you a minimum of 100A (1200W) charge rate at idle no matter what the sun is doing. You could then add a solar system on later (you might get 400W on top of a WildAxe).

If you're buying new then specify a Heavy Duty Alternator, it'll give you more options and not have to work as hard.

Edit: I wouldn't advise going to a Solar only Specialist, go to someone like eddievanbitz who can advise you on both Solar and B2B charging systems.

Cheers
Red
 
Mar 23, 2012
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I think if you want off grid in winter and quit a lot of load even with all the solar you can put on it's going to be a struggle. Are you looking at areas where you are likely to be alone well away from other people it could be a generator is a good bet with largish battery capacity.

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Feb 14, 2021
2,918
6,012
Milton Keynes, UK
Funster No
79,219
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Burstner Lyseo 727G
Exp
19 month year 18000 miles UK, Ireland, France, Spain, Germany, Italy. Campsites and off Grid.
Yep, the more the better.
Depends on your usage patterns. I have one 175 watt and have never run out of power (or anywhere near). The only reason I might want more is if I stayed put for more than 2 weeks and the sun wasn't shining. (I wouldn't go somewhere for 2 weeks if the sun wasn't shining!) We tend to move around a lot and travel April - November. Mostly in southern Europe. So for me buying more would just be waste of money.
 
Apr 27, 2016
6,555
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Manchester
Funster No
42,762
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A class Hymer
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Since the 80s
Will want to stay put for a week or more regularly.
Use? 12v TV, recharge phone, mifi, occasional inverter for laptop etc., winter lighting, ....
These look like fairly modest requirements. Be careful of using an inverter, it sounds like an easy solution but can be very wasteful of battery power. For a laptop which probably takes no more than 100W you could almost certainly find a 'laptop car adapter' that plugs into a cigarette-lighter type socket. It will give you the 19V or so that the laptop requires. You can get a universal type with a selection of 'tips' to fit the laptop socket.

If you definitely need an inverter then the smallest one that will do the job is better. They take a constant background drain, even when nothing is plugged in, so best to switch it off if not actually using it.
 
Feb 14, 2021
2,918
6,012
Milton Keynes, UK
Funster No
79,219
MH
Burstner Lyseo 727G
Exp
19 month year 18000 miles UK, Ireland, France, Spain, Germany, Italy. Campsites and off Grid.
In addition to Lenny's comment, I think you'll find you won't have enough "real estate" up top to service your requirements, other than in summer.

I'd go Lithium (at least 1Ɨ 300Ah) and 120A B2B, this will give you a minimum of 100A (1200W) charge rate at idle no matter what the sun is doing. You could then add a solar system on later (you might get 400W on top of a WildAxe).

If you're buying new then specify a Heavy Duty Alternator, it'll give you more options and not have to work as hard.

Edit: I wouldn't advise going to a Solar only Specialist, go to someone like eddievanbitz who can advise you on both Solar and B2B charging systems.

Cheers
Red
Over kill! There is nothing in his list there that uses much power (assuming the lighting is LED). I can stay off grid for a week (not moving) with 175watt and 180 ah of AGM (effectively 90 usable). The only problem would be if there was no sun.

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