Electricalist advice!

jumpinjackjones

Guest
Morning team!

Am Almost finished converting my tiny van into a tiny stealth camper, but have a little question.

I will be using a battery in the back to power a 12v light, a car stereo and a 12v plug socket, which i will keep topped up using a solar charger as it will hardly be used.

I will be running the cable from the battery to a junction box with three switches in- one for the light, one for the stereo and, you've guessed it, one for the socket! Do i need a fuse anywhere, and do i need to earth the neg terminal to the side of the van?

Thanks in advance for any info...

Chris
 
electrical

Hi Chris
The answer to your question is yes you should put a fuse as close to the battery as possible to protect against over loads and fire. The car battery is capable of delivering well over 500 Amps which if a short occured or a fault in an appliance without a fuse may over heat the cable resulting in an unwanted fire. The fuse should be choosen such that its capacity is less than the current carry capacity of the conductor. Sat for 6mm cable I would use a 15 amp inline. How big is your solar panel and what type of charge controller are you using? as a matter of interest.

cheers Lazy
 
Havent a clue! havent bought my solar panel yet, or battery etc.

have spent last week insulating the walls floor and ceiling, carpeting, making a bed and storage...

am starting with the electrics tomorrow...

i would be hugely grateful if you could walk me through my little set up!

as it stands at the moment, in my head, i have a battery under the floor, flex from the battery to an adaptable box. the live from the flex goes to a terminal block, which has three lives coming from it, one to each switch.

whats a charge controller?!

Sorry to seem so thick... am learning!
 
electrics

No problems
This is my feild. Ok the solar panels job is to replace the energy you are going to use each day. How big your battery is is dependant upon the energy you use each day. If you can tell me the wattage of the items you are going to use I can tell you what size battery to buy. what size solar panel is needed and charge controller. The charge controller is a relatively in expensive item but maintains the appropriate charge level to the battery ensuring long battery life. If the van is parked for awhile the solar panel would over charge the battery and shorten battery life.
When we talk about battery we talk in terms of energy needed and DOD (depth of discharge) the greater the depth of discharge the shorter battery life.
Any way back to your question. You have a battery under the floor to run your loads. Is it connected in to the engine charge circuit?
from what I understand you have 1 cable pair with earth coming from your battery and you intend to run 3 items from it . This is ok providing you put a fuse on the run as close to the battery as practicable. The fuse is only there to protect the cable. The down side of running only 1 cable is that if the fuse blows everything stops. The biggest failing that most people make is using too small a cable. keep cable runs as large as is practical and as short as posible with in reason to reduce volt drop.

Energy you need equals wattage by the hours of use. The the amp hour you need = the energy divided by the battery volts say 12. lets say I am running a 60 watt fridge for 10 hours then the energy is 600 wh. the amp hours I need = 600/12 = 50 amp hour. allowing for a DOD of 50% that to get good battery life = 100 amp hour deep cycle battery.
solar panels. In the UK you get about 5 PSH that is peak sun hours where the suns irradiation is greater than 1000mW per square meter. That means you have about 5 hours to charge you batteries. hence you are using 50 amp hours. then divide by PSH = 50/5 = 10 amps per hour. or approximately 120 watts of panel.
This probably too much in 1 hit but if you take it step by step happy to help.
Are you using house hold wiring cable?

hope this is not too confusing

cheers Alex
 
far too confusing, but if i think long and hard about each sentance, it looks english!

i haven't bought anything yet... at some point today i will be buying a bog standard nothing special car stereo from halfords... a single light... and a single socket from maplins!

my plans are to use the light for an hour every time i use my van which will be most weekends and every now and then in the week... the car stereo at the same time as the light and the socket for my pump up mattress pump!

i will go now and buy these and give you any information that is printed on them!

i havent yet got cable, fuses etc..

your help is hugely appreciated, mr lazy!
 
and by the way, i was planning on having this run totally seperately to everything else... might consider a split charger as opposed to a solar panel... but the new battery will be about two metres from the engine battery, or i could put the new battery next to my existing battery, but then these would be two metres or so from the appliances...

this may be irrelevant, but just giving you all the info i have

chris
 
Just one or two small points that may apply to your specific situation.

The rating given to solar panels is a purely theoretical figure useful only to compare one panel with another. A 120W solar panel will never provide 10amps into your battery no matter how sunny the weather. 80Watts (about 7 amps) would be more realistic under actual conditions and that would only be if the panel was mounted at the correct angle. It is true that the latest technology in solar regulators will make more use of the available output (but rarely as much extra as they claim unless you are living around the Arctic circle, but even then, the nominal rating figure is still not a practical figure.

For panels mounted flat on a roof, I would suggest that 5 PSH is also a bit optimistic for most anywhere in the UK except on a perfect summer day. In real life, average conditions never seem to prevail when you need them most.

Better to be a bit pessimistic even when it is hardly a big deal if you run out of power.


Generally speaking, the negative side of the battery is connected to the chassis of the vehicle but in your case, if the body of the camper is not metal, and if you do not interconnect to charge from the alternator, there may be little point in doing it. Just run two wires to each of your loads


http://www.ccis.com/home/mnemeth/12volt/12volt.htm parts 1 and 2 will give you a fairly good basis for becoming an "expert" in the RV field. Far more comprehensive than you need, but ... Obviously a bit "americanised" and slowly getting out of date, but still all good knowledge

If you intend to camp for a day or two and then drive for an hour or two, you may also like to consider installing a manual or automatic coupling switch or relay to allow your engine alternator to recharge the leisure battery as you drive. If you are just a weekend warrior, you may be able to do without solar entirely - at least until you have had enough experience to know what your lifestyle is likely to be.
 
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solar panels

Hi
And quite right a solar panel rated at 120 watts would never give 120 watts, I didnt want to go that far but to open the box. Sor panels are either mono poly crystaline or amorphous. each have different characteristics and need to be derated for temperature and solar efficiency. That is .5% for poly crstaline for every degree above manufactures rated temp based on actual cell temp and 045% for mono crystaline for every degree above manufacturers specs cell temp Amorphous performs totaly differently and we dont as a rule derate for those panels. In addition we need to consider manufacturers tollerance and the level of soil. However I though my earlier answer was confusing enough with out taking it further.

cheers Lazy
 
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Hello, can I add my own specific and most definately practicle experiences, after reading, asking and calling a lot of experienced people I purchased a 60 watt panel intending to always have it portable and pointing in the right direction.

The balance of the, 'close to £900' I needed to spend for green energy collection went into a wind turbine on the basis I mostly camp where I can kitesurf.

Once I had rigged my solar panel and wired a regulator into the system together with electronics to feed my engine battery and keep it .7 volts under the leisure bank I did the tests of pointing at the sun like a roof-fitted panel then tests pointing the panel at a low sun. The difference was astounding, I would say that the claimed 5 times power increase by the solar-panel manufacturers that make the self-seeking ones is an under-estimation. I once read a difference of 10 times but thats a purely unscientific claim that I can't give figures for or validate the current/voltage reading.

Suffice to say I will never fit a solar-panel and point it at the sky above me unless I'm near the equator.

The wind-turbine is terrific, it works quietly all night long and sometimes for days on end, Ok, in the summer a solar panel rules.

dscf0018xr9.jpg
 
solar direction

Hi , I dont know where this is heading but why not
Yep you are 100% right a focused collector will allways yeid far more than a fixed collector regardless of the angle. Havng said that my point was that if youre in a mobile rig the best irradiation can be achieved fixed on plane to the roof. Putting em away whilst you travel yeids nil. Wind turbines have their advantages when sationary.

here is a picture of me and a few mate on our last camping trip.
note the shadow of the 1.2 k wind turbine
ClassOf2008



Na its my class from 2008

enjoy your day
 
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Did I take this thread off-topic ?

If you posted a link or a photo I got a little question mark instead. By-the-way. The reason for the tiny Rutland turbine is that I couldn't rig even the next size up by myself in a 15/20 knot breeze and off-course I needed to store the turbine when it isn't in use.

As regards a fixed solar panel collecting whilst you travel I'm fairly sure the 'Electroblock' takes a charge from the alternator as we travel.

More than the odd one or two commenters have commented on the risk of having the panel stolen, yes its a risk. I secure it and I stow it, other than that I keep an eye out.

Sorry if I went off-topic.

Richard.
 
Noody said

I would say that the claimed 5 times power increase by the solar-panel manufacturers that make the self-seeking ones is an under-estimation. I once read a difference of 10 times but thats a purely unscientific claim that I can't give figures for or validate the current/voltage reading.
Click to expand...

yes, anywhere in the north of scotland in the middle of winter. Who goes to far north Scotland in the middle of winter AND relies on solar power? Go to Iceland and the difference might be 10 or 20 times, but what is the use of getting a watt or two from an 80W tracker instead of zero from a flat panel. Advertising puffery designed to impress the innocent.

In countries where solar is a viable way of producing power, the difference that a multi-thousand pound tracker can make can be obtained merely by adding an extra panel flat on the roof. That way you don't have an expensive bit of heavy gear to wipe off the roof when you forget to lower it. And when it is lowered, a tracker may not produce any power at all. Saw one recently that was a combo satellite dish/solar panel. One or the other, not both at once. As long as you don't spend all day watching TV ...

Any practical RV application for full-timing is going to need more than the usual 60 or 80W single panel anyway.
 
wind

Hi
I have enjoyed the chat but was a little concerned that we may have made a question for person seeking answer more difficult than it need be. You are clearly experienced and have a good grasp of the electrics.
I think
The question was should I fuse a circuit running 3 loads and the answer is:

.

You should use the charge system already connecetd to the vehicle to charge your load battery but have an isolator so your load wont discharge your main battery.


You should use a charge regulator to charge batteries from a solar panel.

All fuses should be as near the battery as posible.

Your battery should be sized against the load. (the battery being the heart of the system)

Haveing said that every thing that has been said on this thread is correct.

In Australia I have 160 watts mounted to the roof of my Hi-lux to run every thing and 210 amp hours of sealed lead acid batteries. A plasamatronic regulator.

My home runs from solar also 680 watts of panels on the roof 1400 amphours of battery and a 300 watt wind turbine.

And I take your point theft is a problem but not so much where I live.

140 watt panels I sell in Aust for about $1200.00

Picasa Web Albums - Energy-wise - Class of 2008 hope this link works


Thanks for the interesting chat
best regards Lazy
 
Just trying to get pic down to a size where they will fit
cheers
 
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Thanks Lazy, sorry you had to catch-up after I diverted the thread. Tony I'm so pleased you pointed-out that paying for the extra surface-area is better than all that paraphenalia on the roof.

I won't make any comments on 12V safety because 'Lazy' has just about covered it. My only contribution is that a lot of people think 12V is harmless, if you fit into that category I recommend you get help before you melt your van.

Fuse = safety
No fuses = disaster

Richard
 
Lazy

Just gone through all the photo's, fabulous. I live on an old Farm site in a warm valley in the far-west of Wales and even though the weather can be trying I believe we still get enough sunshine to warrant the investment into solar and wind power. We have the space and I'm sure we could have planning approval.

I worked on some plans and the resulting figures of a decent sized turbine together with inverters, suitable accumulators and some professional help came to £30.000.

I didn't do any work on the solar collectors.

Thanks for the input Lazy.
Richard
 
now reeling everything right back to basics folks!

I'm just looking to cheaply and simply have a bit of electricity in my van!

Tell me whats wrong with this...

A car battery which i can pick up for free tucked behind my van battery connected to it using a split charger which will charge it when the engine is running but not draw off my van battery.

some 1.5 twin and earth from the battery to my box of switches which is about two metres from the battery with an inline fuse close to the battery.

I know a leisure battery is better because it will last longer etc but theyre also expensive, and as i camp in my van only occaisionally i dont want to spend! all i want to do is use my van as i do now but with no danger of draining my battery and not being able to start it!
 
You can't use 1.5 T&E, the cross-sectional area will be to small to cope with the current you are likely to draw at 12 V.

At 240 V the current draw is very small for a given load, the same load will draw a lot more current at 12 V, as the voltage drops, the current increases. Sorry I can't make it more simple than that and I won't give you figures that may confuse you.

At 12 volts you won't get a shock, the danger is the huge current increase that sets things on fire.

Best bet for you is to work out the load you are likely to use, add a bit for safety then take the figures to someone who can advise you the correct conductor size.

I don't actually know the correct ratings for cable, just look at these simple figures.

240 Volts with 1/2 amp passing through produces 120 watts
12 Volts with the same current passing produces only 6 watts.

The difference between 120 and 6 is X 20 and hopefully steer you in the right direction to understanding the different size cable you need to use if you intend passing.

I really don't know how to simplify this more than saying there is 20 times difference between 12 Volts and 240 Volts so if you use conductors incorrectly you are going the start a fire by melting conductors. Another point is you need flexible-multi-strand for vehicles.

Richard.
 
my loads are one bog standard car stereo, one six inch long 12v flourescent light and one 12v socket.

how is it so complicated?!

can anybody tell me what size cable and fuse to use on this, which must be the simplest circuit ever in a campervan?!
 
Its a bit difficult because you don't know the load you may use at the socket.

I'm trying, Ok.

If you use 20 amp multistrand, fuse it down to 15 amp at source then sub-circuit fuse the audio and lighting then finally the socket. Or you could use multiple runs of 10 amp cable but always use inline fuses at source and for sub-circuit protection.

You get stuff here. There are other sources. Why not go to a self build forum, you'll get some good advise there.

Cables & Connectors

Richard.
 
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