Off grid electrics
Getting a constant supply of electricity may be the biggest challenge for someone living off-grid.
Electricity is regarded as so important to modern life that the EU disaster zone countries have started taxing it on the basis that no one avoid the tax because no one can live without electricity. In Malta they charge foreigners more for their utilities . So much for a common market!
Presuming that you are going to use a solar panel to charge leisure batteries , the components are, in order : solar panel - charge controller - leisure battery - inverter.
If you a living in a vehicle you may also want a multi-battery charger so store up some current when the motor is running.
You may also need a multimeter , power meter, 12 volt sockets, 230 volt sockets, inline fuses, some cable and maybe a battery charger.
12 Volt items connect straight to the leisure battery. Remember some in line fuses in case something malfunctions.
Multimeter
These are about £8 from maplin. I bought some online but they were very bad quality, shit actually. Multimeters have a lot of settings and functions. The only test I have ever done is to turn the dial to "20", which presumably means under 20 volts. Any battery that reads below its stated value should be considered "empty". Values above the stated value are exponential. So a 12v battery with a reading of 13v has much more than twice as much power as one reading 12.5v.
Remember to turn your multimeter off to save the battery.
Multi-battery isolator
In your vehicle a cable runs from your alternator to the live terminal of your battery. To fit a multi-battery isolator you need to cut into this cable and connect it the third terminal runs to the leisure battery. Once fitted you can drain the leisure battery without affecting the vehicle battery. 12 volts is quite low so paradoxically the cables need to be thick, more than 6mm is good. Jump lead cable is good failing that cable can be obtained cheaply from a scrap metal dealer.
You can do without a multi-battery isolator if you just have a switch that you turn on after the engine is running and off just before you turn it off. A cooker switch fits the bill. Don’t forget to turn it off though.
The earth terminal of your leisure battery is connected to the chassis of the vehicle. If you live on a fibreglass boat you will need a separate cable leading from the earth terminal of your leisure battery to the earth terminal of the boat battery.
Two different sizes. I don’t know the difference in functionality.
Leisure batteries
Leisure batteries look like ordinary batteries but have vastly different functions. The job of a normal battery is to start the engine and then get re-charged as quickly as possible. Leisure batteries charge and discharge slowly. Probably about five hours. They work very well with solar panels for this reason. Leisure batteries are rated in amp hours ( AH ) . I have two 85AH batteries.
Leisure batteries can give you the little bit of electricity that makes the difference to your life. Mobile phones are the top of the list but 12 volt lighting, DVD players and portable TVs and radios need electricity too. Some types of heating need electricity together with the diesel / LPG fuel. It’s quite alright to fit solar panels horizontally. Slightly better to pitch them to the sun but it does not make that much difference. The price has come down in the last few years from £2.50 per watt to £1.50.
On the downside, Solar panels have to be positioned where they are visible. This attracts the attention of thieves who will know you have all that hardware. Also it tells busy bodies that you are living there.
Inverters
Inverters convert DC to AC. I don’t know why they aren’t called converters. You will obviously want one that changes 12 volt DC to 230 AC. ( There are some 24 volt ones but you would need two 12 volt batteries ) . I have three inverters : 75, 350, 1000 watt. Experts say that they are 25% inefficient but they also seem to draw more power for themselves depending on their capacity. Some squeal and turn themselves off if the load is too much or the battery too low. An annoying feature is that the fan keeps running so you may think the inverter is running if you weren’t there when it was squealing. The problem needs to be solved and the inverter turning off and on. Try to avoid inverters all together by getting portable equipment that used 12v directly. Never leave your home with an inverter running. Two of my 75W ones have blown up.
75, 350 and 1000 watt inverters
Items often have a start-up surge . This is where they draw as much as five times their normal running load for a few seconds initially. Unfortunately this will trip out an inverter that could quite happily run the item otherwise.
Large inverters need even more leisure batteries and some way of charging these. It is better to find gas powered alternatives. It is difficult to imagine an off grid alternative to a domestic washing machine. They need too much water and power and the clothes need drying of course. I use a launderette.
12 Volt Sockets
Some 12v sockets have a USB port as well. USB ports are 5V if you were wondering.
Remember to connect these up with an in line fuse .
These are great but the wires inside often break, so keep the receipt. If the wires break after the guarantee has expired you can solder the electrical connections back with more flexible wire.
Battery Chargers
If your battery is flagging it may need some special help. Battery chargers have evolved over the last few years. The old style ones just pumped electricity into the battery.
These CTEK chargers can rehabilitate a battery that has been mistreated (run low and left there or run low repeatedly ). These battery chargers evaluates each battery and performs accordingly so you can only do one at a time in case they have different problems.
Proving that size is not everything. These chargers are available online for around £40.
You might find yourself in a situation where your home has no method of charging a leisure battery. It’s very frustrating to know that your battery could be charging at work or whilst you are driving. In this case some quick release battery terminals come in handy. You will get tired of lugging a battery everywhere though.
These 230v AC power meters cost around £15 and are excellent for tracking down your power hungry utilities and for checking start-up surges.
Lighting
Inefficient lighting produces heat instead of light. LED light bulbs are better than traditional bulbs. If you intend to live in an existing boat or motorhome etc. It may well be worth replacing the whole lighting system with a 12 volt LED system.
Notice the connectors are thin all throughout their length. Connectors with tiny metal cylinders on the end are 230V AC not 12 volts DC.
Solar Powered mobile phone chargers .
These are available if you are sure a mobile phone is going to be your only electric device.
My System
My solar panel is 60 Watts and cost £90 . This is enough during the summer . The sun is up longer so the batteries get a full charge and I need lighting for a shorter time. I will get another solar panel before winter. Leisure batteries are rated in amp hours ( AH ) . I have two 85AH batteries which cost £100 each. In retrospect I would be better off with one battery and two solar panels.
I have three electrical circuits: One for 12 volt DC, one for 230V AC through a 75W inverter and another for 230V AC through a 1000W inverter. The latter is only used for the microwave and a power tool if necessary. Everything should be turned off when you are not being used.
Battery Maintenance
It is important to look after your batteries. Every six months the acid levels should be checked. To do this , firstly clean the top surface so that no debris gets accidently brushed into the chambers. Prize the caps off and check that the acid covers the plates. If it does not, top each individual chamber with distilled water AKA de-ionized water.
Most items won’t work if the voltage drops below 12, but is still possible to drain the battery further with a light bulb. You should only dip your batteries below 12 volts briefly if at all. They should be recharged as soon as possible.
If an automotive battery is giving you cause for concern check that the terminals are working correctly by seeing how tight they are. Also check the voltage between the battery terminals is the same as the voltage between the cables. A difference greater than 0.02 volts means that the terminals are not tight enough. When the engine is running the voltage should read 13.5 volts, below this and your alternator may be malfunctioning.
If a leisure battery is giving you cause for concern do the same preliminary checks on the battery terminals. A solar panel should be producing 13 volts. Check that the voltage going in and out of the charge controller are reasonable considering the lighting conditions.
Once the source of charge has been removed. IE the engine has been turned off or the sun has gone down, disconnect the battery concerned completely. Monitor it every five minutes and make a little "back of the envelope" graph. Voltage Vs time. If the value settles above 12.8v. The battery is OK.
Reconnect it to whatever it was connected to before, but with everything turned off. Continue the same graph. If the voltage drops you have a leak. Disconnect everything and reconnect items one by one to find what’s causing the problem.
Domestic Appliances
The wattage of various domestic electrical equipment is:
So how much power can you expect from you electrical system ?
Wikipedia says that :
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance, one arrives at the usual mathematical equation that describes this relationship where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms.
thus : I = V / R
No I haven’t got a clue what that means either.
A more user friendly version is :
W = A * V or rearranged to A = W / V where the symbols mean Amps, Watts and Volts.
So let’s imagine that you want to run an item that is 60 watts from a 12 volt battery. Using the second equation Amps = 60 / 12 = 5 . So that’s five amps then.
If you had one 85 amp hour battery so it should be OK for 85 / 5 = 17 hours. In practice using this equation will give you a unrealisticly high expectation of your batteries because of a few factors :
Some experts say only to use half of the stated amps .
Peukert’s law says that if a battery is discharged quickly it contains even less power than you might expect .
The more often a leisure battery is discharged fully the sooner it will need replacing so it is best to work well within the batteries limits .
Inverters are about 25% inefficient .
The declared amp hours are often over stated .
All this is partially confirmed by the fact that things seemed to be OK whilst was the sun was shining on my solar panel and went down hill after sunset .
It is best find a gas powered alternative rather than buying more and more leisure batteries and solar panels .