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Solar And Wiring


wigelywoo
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msg-10-0-90544000-1394276302_thumb.jpg Hi
I have put a pic of what I am contemplating doing with my caravans wiring. I would like to just have 2 wires on the battery. I would like to run the 2 wires from the battery to the inside of the caravan where the Inverter, Mover, and Solar Regulator will be under the front seat. The leads would go from battery to inverter to motor mover module to solar reg with existing caravan leads connected at the inverter.

Also do I need any switch on the

Solar side.
Many thanks

post-10-0-43039600-1394611586_thumb.jpg

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No switch on the solar. Keeps number of connection to a minimum.

 

A tip: If you ever need to disconnect the battery you should release the positive feed from the solar into the controller. I had a controller show a fault condition when I failed to do this. The fault only showed when I reconnected the battery. (the battery needs to be connected to the controller before the solar not after)

 

 

What size invertor? These may need their own leads direct to battery.

Ford C-Max and Coachman Festival 380/2 SE 2006    Motto  Carpe Diem

Still trying to find the perfect pitch. ..110 amp Battery+ 65 watt roof mounted Solar and 25 watt Wind Turbine. LED lighting. Status Aerial 315. Loose chattels marked with UV,. Safefill Gas Fitted.

 

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The system desperately needs some fuses and the inverter also must be switchable. The size wires for the solar system are oversized.

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An 800W inverter would draw 67A with a surge current twice that. If connecting the motor mover to the Inverter (as opposed to directly to the battery), the leads to the battery would also carry this load at say 50A on average with a surge / or heavy load twice that, plus then the normal caravan loads at, say 15A. This means that you'll need to fuse the battery lead at 249A and to protect the battery leads from short circuit, your cable would also need to support this so you're looking at 35mm2 at a minimum. In this scenario, 10mm2 would be dangerously under-rated. I'll give you that it's unlikely all these devices would all be on simultaneously but you should always design in a worst case scenario.

 

I would humbly suggest using a DC distribution box (like this one) and individually fuse each circuit.

 

To support surges, you should fuse your inverter at a minimum of 134A (i. e. 67A x 2), which would mean your cabling would need to support at least this to protect from short circuit, so 25mm2 would be required. If you're willing to accept the fuse blowing under high surge conditions (or buy time-delay fuses) then you could potentially reduce the fuse to, say, 100A and inverter and battery cable size to 16mm2.

 

As mentioned above, the 6mm2 cable would support up to 50A, though your controller would never supply more than 17A. To reduce voltage drop to a minimum I would tend to over-specify solar cable so would recommend 4mm2 solar cable.

 

Your motor mover would need to support maximum (heavy load) current so a 100A fuse would require 16mm2 cable. Some motor movers require much more than this - check out this article.

 

See attached for my suggested logical system diagram.

 

There is an argument to fuse the positive battery lead but, I'll admit, I didn't in my recent installation - find an interim photo this attached (it's a bit messier than this now!).

 

If you did want to keep to your design, I would recommend up'ing the cable sizes per the discussion above and using in-line fuses, such as this one, to protect the device and cabling to each circuit.

 

Edit: added additional info

post-63455-0-60372700-1394620615_thumb.jpg

post-63455-0-65186100-1394620639_thumb.jpg

Edited by tictag
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The fuse in the battery lead is to help prevent a direct short circuit across the terminals via the cable connections.

 

It can catch fire or explode without one.

Ford C-Max and Coachman Festival 380/2 SE 2006    Motto  Carpe Diem

Still trying to find the perfect pitch. ..110 amp Battery+ 65 watt roof mounted Solar and 25 watt Wind Turbine. LED lighting. Status Aerial 315. Loose chattels marked with UV,. Safefill Gas Fitted.

 

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The fuse in the battery lead is to help prevent a direct short circuit across the terminals via the cable connections.

 

It can catch fire or explode without one.

 

I do tend to agree with this and I may yet add an in-line to my installation.

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Due to me being unsure about the cable sizes I put 10mm and 6mm as I thought this is what I had. The original cables that came with inverter, on the left, and, mover, on the right.

 

 

post-10-0-41448900-1394642976_thumb.jpg

 

Please see pic on my other post,

Thanks

Edited by wigelywoo

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I can't quite make out the diameter on the image - it's too small. Just remember that the cross sectional area A = pi x radius squared. For example, a 10mm diameter conductor would have a cross sectional area of 3. 14 x (10/2) squared = 79mm2 or put another way, a 16mm2 cross sectional area cable would have a diameter D = 2 x root (area / pi) = 4. 5mm.

 

I've suggested using 25mm2 (or 5. 6mm diameter) cable for the inverter and 16mm2 (or 4. 5mm diameter) cable for the mover.

 

Hope that all makes sense.

 

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Thanks tictag

Better pic here

http://www. caravantalk. co. uk/community/topic/92597-cable-sizing/

 

 

I cant understand why admin moved one post to electric but, not the other

Lunar Zenith Citroen C5 2. 2 HDI Citroen Picasso 1. 6 HDI. , Vauxhall Vectra Design 150 bhp Soon to be, 2014 Sprite Major 4 sr. With ATC.
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It looks to me that the one on the right is 5mm (or circa 20mm2*), and whilst the one on the left is a bigger cable, the conductor is actually smaller at around 4mm (or circa 12mm2).

 

* 5 / 2 = 2. 5 ^2 = 6. 25 x 3. 142 = 19. 6mm2

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Thanks tt

The one on the right is the Motor Mover supply, I have as 6mm on the wiring diagram

The one on the left is supply to inverter. I have as 10mm on wiring diagram

Maybe I should just use the cable on the right.

Lunar Zenith Citroen C5 2. 2 HDI Citroen Picasso 1. 6 HDI. , Vauxhall Vectra Design 150 bhp Soon to be, 2014 Sprite Major 4 sr. With ATC.
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The actual cable CSA will in fact be less than the simple PI calculation above because it is not a solid conductor. Stranded cable also contains a fair amount of space between the conductors.

 

Tony

Thanks tt

The one on the right is the Motor Mover supply, I have as 6mm on the wiring diagram

The one on the left is supply to inverter. I have as 10mm on wiring diagram

Maybe I should just use the cable on the right.

I'd suggest that is way undersized for an 800W inverter that can draw up to 80A from the battery.

 

Tony

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20mm2 flexible automotive cable supports 135A so you will need to fuse at up to this value and no more. Your inverter could surge at more than this so you may end up rupturing the fuse but in normal use you should be fine.

 

It's obviously designed for your motor mover so (we assume!) is suitable.

 

You could use the smaller cable for your solar controller? It's actually bigger than you need.

 

I would still be concerned about the cable leading to the battery. Firstly because of the lack of circuit protection in your design but also a scenario could present itself where the inverter & motor mover and 'van electrics are on (there is nothing actively preventing this scenario in your design) and using even 20mm2 cable would be dangerously under-rated.

 

Still, you know the risks. ...and tomorrow you could get run over by a fork lift truck.

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20mm2 flexible automotive cable supports 135A . ..

As long as the run is no more than a metre or two from the battery, otherwise voltage drop will be a killer.

 

Tony

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I would humbly suggest using a DC distribution box (like this one) and individually fuse each circuit.

 

:goodpost: I would fully agree with the distribution box, makes everything so much tidier and adds a great deal of safety,, may only be 12V, but boy can those cables get hot under a short circuit or overload condition.

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As long as the run is no more than a metre or two from the battery, otherwise voltage drop will be a killer.

 

Tony

 

A good point. A 20mm2 solid copper conductor has a resistance of about 0. 8mohms per meter (more if stranded), which at the maximum rated current of 135A would drop about 0. 11V per metre. A 6 metre run (3m +ive out, 3m -ive back), for example, would drop 0. 66V, which means that, aside from the resistive losses, an inverter designed to switch off at 10. 5V would actually do so when your battery was at 11. 2V.

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Actually it would be worse than that because as the voltage dropped the inverter would pull a higher current to keep the power the same. The higher current would increase the voltage drop etc. ..

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A re-measure of the cable on the left is 5mm, and the cable is the one that came with the inverter and is 1. 200 mm long.

As the inverter will be mounted behind the battery box, it will be reduced in lenghth to 300mm_400mm max.

Am I wrong in thinking this will carry the load?

The inverter is switchable and there is no reason to have it switched on, when mover is in use. charge from SP will also be switched off, before regulator, when mover is used.

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A 5mm (or 20mm2) diameter automotive cable will support 135A. Your inverter's continuous max current is 67A (800W / 12V = 67A), though could surge to 134A. A 0. 8m run (2 x 400mm) would drop around 0. 1V, so negligible. I would fuse the circuit at 135A, keep the cable in free air and you should be fine.

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Thanks tt

 

Is the switch before the Solar Reg, to allow battery swopping ok?

Edited by wigelywoo

Lunar Zenith Citroen C5 2. 2 HDI Citroen Picasso 1. 6 HDI. , Vauxhall Vectra Design 150 bhp Soon to be, 2014 Sprite Major 4 sr. With ATC.
The Internet has had no effect on my life whatsoever. com

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