Like with the gas installation (and everything else come to think of it) I did a S**t load of research and decided I could do it on my own... Its not that scary once you get started! This page is meant as an introduction into the things you have to think about for this stage of a conversion-- not a step by step guide..
After reading my intro join the Self Build Motor Caravanners Club. Pay the £15 to be a full member and you will get your money back in knowledge, advice, discounts and time.. The forum has everything you need for any part of a conversion, especially the confusing bits. Also read this book because it explains in easy language everything you need to know about this bit-- Do It Yourself 12 Volt Solar Power by Michel Dainek.
Now about my system and how I made it.... lots of writing then pictures ...
To put it plainly I have 4 big solar panels which charge 4 big 12v Batteries through a 'charge controller'. I can also plug into the mains to charge them if its available. From the batteries I can directly run 12v appliances or use a 'pure sine wave inverter' to turn the 12v battery power into the same power you get from the mains in your house..........
So far>>> Solar panels > Charge controller > Battery bank > power feed to inverter/ direct to 12v appliances
- THINK ABOUT WHAT YOU WANT TO RUN to decide WHICH BATTERIES YOU NEED>>>
The main things I use:
- 12v Warm White LED's (1.7W or 0.14Amps) - 16 of these seems a lot but its a big truck and they use little power anyway!
- 12v Diaphragm Water pump: (48w or 4 amps approx)- more power usage but its only on for maximum 15-20mins a day (if that)
- 2x usb ports + cigarette lighter style port- >Devices with batteries (phones/ laptops etc) mostly charge of lower voltages- For example the box attached to your laptop charger just changes the 230v from the mains to around 18v for your laptop battery. To charge off your new12v battery bank you could use an inverter to push 12v into 230v and use the normal charger to go back down to 18v but this is inefficient. I bought a 12v 'car charger' off amazon that goes into a cigarette lighter type socket to solve this wastage. (match the rating on your laptop with the new charger to get the right one)
- My 4 big old stereo speakers run off a JL G4500 car amp I got for £50 on ebay... Its '12v' but hard to say how much power it uses as this more depends on how loud the music is...
- Speakers =8ohms amp = 4ohms- bridging the amp chanels from 4 to 2=180w/ channel @ 4 ohms so I run my 8ohm speakers in parallel to achieve 4ohms- (If you like your big old stereo speakers like me then look this up so you can use them in your van with a car 12vamp instead of a mains powered 230v amp)..i think its worth it..
- I wired two Standard uk sockets to the inverter to power things that do not run on 12v like a sewing machine (I like to sew..)
WATTS (W) = AMPS (A) X VOLTAGE (V) AMPS= WATTS / VOLTAGE VOLTAGE = WATTS / AMPS
The Ampere rating of an appliance is the current it draws from your battery bank. Its a bit useless until you relate it to the time this current is drawn for... This gives you Amp Hours (Ah)- Simply multiply the current (A) by the time you roughly use it for each day (Hours). so...
e.g: a 10w light will at 12v will draw 1.2A. if its on for 5 hours in the evening you have 6Amp hours (Ah)
The Leisure Batteries needed for a Battery bank are rated in AMP HOURS... So you can get an idea of how big your battery bank needs to be to power all your appliances by figuring out how many Ah all your kit draws.... Bimble solar have good info + an easy table here
- Batteries in SERIES= a string with positive connected to negative.. two 12v (@100Ah) batteries in series would give 24v (still 100Ah) battery bank.
- Batteries in PARALLEL (the one we need)= connecting positive terminals to positive terminals and negative terminals to negative terminals- so two batteries of 12v (100Ah) in parallel will give basically one big battery still of 12v but with a combined (200Ah) rating......
- Batteries don't like to be discharged below 40% if possible and you will usually be given a rating for the lifespan in "deep discharge cycles"- mine each have 500 deep discharge cycles (Running a battery flat then re-charging it being 1 cycle)...
- because of this its best to oversize you battery bank so as to be using the "top half" of your batteries as much as possible-- this is explained further on Bimble solar and the sources I recommended at the top of the page..
- Looking after your Batteries by doing this and keeping them charged will extend their lifespan greatly.
- I have 4 Leisure batteries that are each rated at 125 AmpHours..Run in parallel with (+ connected to +) and (- connected to -) it gives me a 12v battery bank with 500Ah to work with.
CHARGE the batteries>>>
Now you have to be able to keep the batteries charged:
-- some options to look into are > 1) A split charge relay (charge of the alternator of the vehicle when its running) > 2) An mains hook up (shore power) > 3) solar panels.. .> 3) A generator but a combination is always best..
4 big solar panels charge my battery bank and so far I haven't had to use the electric hook up I installed as back up and the batteries are well in the 'top half' of their storage most of the time..... The winter in England meant I had to be a little more careful with consumption.
The actual panels you get depend on how much space you have on your roof and how much power you actually need so there are too many options to really cover here.. I did some research and ended up with a deal for the semi flexible type which you can literally stick to the roof. Each rated at 140w (with an open circuit voltage of 26v).
To actually charge the batteries you need a Charge controller-
- option 1 =PWM controller... less efficient but cheap, From what I have read many people upgrade
- option 2= MPPT controller... more ex pensive, up to 30% more efficient + ability to charge low voltage BAT Bank off Higher voltage panels...
Deciding that I needed an Inverter + MPPT controller + Power Hook up (mains battery charger) lead me to a combination product by Victron energy called the Easy Solar.. It combines high spec MPPT with an Inverter and Battery charger= Less wiring and less space taken up and as its a powerful unit I could expand the system in the future to run a much larger off grid set up which I plan to do. Financially it was expensive but still not far off the total of quality individual units.
So my four 140 w panels are run in series in two strings.. Basically makes two 140w panels that have an open circuit voltage of 52v which are connected to two of the three available channels of the mppt controller...
Solar panels > charge controller > Battery bank >
These things are the baseline for a small solar power system. Now you can power all of your stuff... Most of the components for this next part you can get form 12volt planet. if in doubt call them and they are really helpful.
The basics of this> From Battery bank(+) >> fuse box (+) >> (+) appliance (-) >>> (negative busbar) >>> battery bank(-).
Heres a rough idea of what components I use and why... (Again all from 12volt planet)
- Positive from Batteries connected to a 'Mega & Midi Fused distribution Box' with 16mm² cable
- 16mm² cables runs from the 'distribution box' to a first 'Blade fuse box' near the batteries
- A second 16mm² cable runs from the distribution box to the back of the lorry + another fusebox (this saves running so many wires about the place)
- From each fused terminal in a fuse box runs a positive 2.5mm² cable to the appliance positive terminal (via a switch where needed)
- From the appliance negative terminal a 2.5mm² cable runs back to a Negative 'busbar' (this is a bar which you can connect multiple negatives to).
- From the bus bar I then use 16mm² cable which connects to the battery bank negative terminal.
There we have a simple description of a basic circuit where one appliance is run from your setup. If you get to the stage where you install a fusebox and a negative busbar then adding the various circuits for the new appliances is straight forward...
some things to keep in mind>>>
- if your adding multiple 12v appliances to the same feed off the fuse box (like several 12v lights) to run them in parallel to maintain the 12v.
- Fuses are designed to protect the actual cables- rate them just below the capacity of the cable used (A)..
- Switches are useful for turning things on and off but also for finding faults. I have installed big isolator switches between the batteries and the distribution box and on each outlet of the distribution box so you can quickly turn off the power to multiple circuits.
- Soldering connections is a ball ache so Instead I used crimp connectors or loop connectors- (12v planet again) you just crimp on the male or female end and push them together.
- Heat shrink is rubber tube that you can slide over exposed connections and, holding a lighter up to it, it will shrink providing insulation against short circuits.
- I recommend eBay for the actual appliances and 12v planet for the things you need to put it all together.
Thats my intro for the things that need to be thought about 12volts - Like I say Join the self build caravaners club and read the 12v diy solar power book by Michel Dianik and you cant go wrong..