Independently Empowered
'Off grid' means independence, but independence from what? The real reasons for living without that umbilical cord from civilization are psychological and physiological.
Many want to live independently because they fear something is going to happen to the support structure of the city - the web is full of doom-sayers advising to get out. This results in a survivalist view. Once one's independent living state has been achieved the fear of societal collapse may turn to a hope for societal collapse - The more conscious may deliberately try to create a space for more than just their own family, a stage we have gone through ourselves. This is hard, and goes against nature, which is for each family to have its own domain, a space of love, as does every other creature - separate yet in contact, community not a commune. The survivalist view can make people closed in, fearful - not a healthy place to be.
I started out on the off-grid journey because I had become Electro-sensitive to the 50 Hz Mains Electric field that I had been bathed in at varying intensities for my entire life until that point. What I discovered is that being off-grid and independent (and unplugged from the Media Engine) gave me a sense of freedom to think. Once one is able to sustain oneself independently to a degree, you can start to open doors that previously had to remain shut, to look at society from the position of someone who is not dependent on it. If one's survival depends on a structure, you cannot begin to think about uncovering its flaws, you have to keep believing it will continue, that it is the best that can be done. Anyone who openly challenges this has to be labeled insane, paranoid or just plain gullible in order to keep believing in the structure. Once outside, though, one can start to think about the end of the world as you knew it - the end of slavery for everyone.
Many want to live independently because they fear something is going to happen to the support structure of the city - the web is full of doom-sayers advising to get out. This results in a survivalist view. Once one's independent living state has been achieved the fear of societal collapse may turn to a hope for societal collapse - The more conscious may deliberately try to create a space for more than just their own family, a stage we have gone through ourselves. This is hard, and goes against nature, which is for each family to have its own domain, a space of love, as does every other creature - separate yet in contact, community not a commune. The survivalist view can make people closed in, fearful - not a healthy place to be.
I started out on the off-grid journey because I had become Electro-sensitive to the 50 Hz Mains Electric field that I had been bathed in at varying intensities for my entire life until that point. What I discovered is that being off-grid and independent (and unplugged from the Media Engine) gave me a sense of freedom to think. Once one is able to sustain oneself independently to a degree, you can start to open doors that previously had to remain shut, to look at society from the position of someone who is not dependent on it. If one's survival depends on a structure, you cannot begin to think about uncovering its flaws, you have to keep believing it will continue, that it is the best that can be done. Anyone who openly challenges this has to be labeled insane, paranoid or just plain gullible in order to keep believing in the structure. Once outside, though, one can start to think about the end of the world as you knew it - the end of slavery for everyone.
The Practical Journey (so far...)
It began when we first started driving across Europe looking for a place to live, I attached a second battery to the alternator of our car via a relay and a small electric cool-box to that. Before we even set off I learned my first lesson: batteries don't store what they say on the label! (unless they're really expensive).
I have made every mistake in the book, from blowing up alternators by connecting batteries to them wrong (not every red and black wire means + & -, especially in vehicles where white is - ) to destroying leisure batteries in minutes by running a 700W power tool from one (a standard 75Ah leisure battery should not be used beyond about 300W, thats 25A).
Harvesting your own energy from the weather teaches one to be opportunistic in your activities. If you have the energy available and no-where to store it, you should use it. If the energy is not available now, and storage is limited you should put it off - a great excuse to rest and read or take a bath.
I have made every mistake in the book, from blowing up alternators by connecting batteries to them wrong (not every red and black wire means + & -, especially in vehicles where white is - ) to destroying leisure batteries in minutes by running a 700W power tool from one (a standard 75Ah leisure battery should not be used beyond about 300W, thats 25A).
Harvesting your own energy from the weather teaches one to be opportunistic in your activities. If you have the energy available and no-where to store it, you should use it. If the energy is not available now, and storage is limited you should put it off - a great excuse to rest and read or take a bath.
Things Learned
The panel size I recommend at the moment is quite large - to do all your indoor day activities on an indoor type day, ie wet and dark. Think of the things you'll want to do - watch a movie, use lights, operate the water pump etc. Work out what power or current this will use. For example: My new laptop uses 1A when idle or typing, 1.6A when playing a movie, 2.7A on top of these when charging the internal battery. My old laptop uses 2.5A when idle and 5A when playing movie, and has no battery. For lighting, a small (8W tube) strip uses 0.66A per tube, a larger 13W tube uses 1.1A - they get brighter and dimmer according to the battery voltage. Our membrane water pumps use from 4A to 6A depending on how slow the taps are (the slower the tap, the higher the pressure, the more power used). Many caravans have little immersion pumps that use 1.5A to 2.5A depending on the tap setting in the opposite direction - the more water flow, the more power. for each item, multiply the number of amps by the number of hours you expect to use it to get a figure in amp-hours (Ah). Add up all the amp-hours of things you would like to do with electric on a wet day and into the evening. Compare this to the amp-hours you can expect from your solar panel on a rainy day - 5 to 10% of its rated output times 9 hours if pointing upward and no nearby trees. A bright day but where you cannot see where the sun is will be about a 30% day, a storm-dark sky about 1% (I've even known days that were so dark they gave just 0.5%, but they are very uncommon). Then your battery only has to deal with the evening discharge and will last 20 times longer. eg with 30V 8A panel on a 15% day = 25Ah. This will run 3A of lights for 5 hours and play a 2 hour movie while recharging the laptop for another 2 hour movie later.
Last time I checked, (late 2011), there was a massive price discrepancy between UK and the rest of Europe on solar panels. we got ours in Germany, though there is now a supplier nearer to us at similar prices. The difference was about 40% to 100% for the 30V panels and the price per watt doubled again for 12V panels. This doubled also in Europe - 12V solar is a niche market. Grid attach systems work up to a 600V total from 20 panels and then you put another 20 in parallel if you want (you get 20 on a pallet). Prices at that time worked out to about €1 per watt of peak power, and have now approximately halved again to 0.52 €/W (including tax).
A 29 to 30volt output at 7.6 to 8 amps is standard, banded into 220W, 230W, 240W, 250W and priced per watt accordingly. look for a local installer who might be able to sell a single panel - wholesalers only normally deal in pallets of 20.
Most panels are now coming from China. I've gone for poly-christalline, though I looked also at mono-christaline at similar but higher prices but different dimensions both physically and electrically. I expect them to still be working in 100 years time - they are guaranteed for 30 years. Amorphous type panels can be cheaper but I think their lifespan is much shorter (the two small ones we had degraded to unusable in less than 5 years) and they are larger for the power output.
The other key investment is the battery. Until recently I didn't know there was a real choice of battery technology but recently I have become aware of Nickel-Iron batteries as a viable if expensive alternative to lead-acid.
If you are going to buy a lead-acid type battery, I recommend getting a true deep cycle 'Golf-Cart' battery rather than any kind of leisure battery, though we did get a reasonable one 2 years ago, which did about 30% of its 101Ah(Amp-Hour) rating at low power and 120A for 5 mins (it was rated to start a vehicle at 680A). Our battery is a 240Ah golf-cart type. It can do at least 2 complete wash cycles (heater disconnected) and still be only half discharged and still capable of 100A for the spin at the end of that, and I have pushed it to 200A for 1/2 an hour with the chainsaw. It cost us 400€ in a local battery shop in Riverolo, weighs about 70KG and is 2 6-volt batteries linked together with an extra cable. You can probably find a 120Ah true deep cycle of 12V that will be plenty for your needs (don't use more than 1000W inverter with that). If you had a smaller panel, then the Ah deficit per day at 15% will accumulate. The battery will suffer if over-discharged (below 11.6V) or if left mostly discharged for more than a night. In one week, last year, the above mentioned 'good' leisure battery lost about 25% of its capacity (it had hardly degraded at all in the year before that) when we had a dark week and had discharged the battery at the beginning (this was before the new panels - we only had 3.5A at full sun, meaning just 0.35A between us all in that dark week). The other, older batteries were all pretty much ruined by that week and have all failed completely since then. The chemistry of lead-acid batteries forms lead sulphate in a reversible way as it is discharged. The lead sulphate, though, if left for a while (like a few days), changes to a different form which cannot then be split by the charging current, and battery storage capacity(Ah) and current (amps) ability is lost. If you use lead-acid, batteries are a consumable ongoing cost of off-grid solar. Making them last and requiring less storage is the reason for the large size of panel I suggest. A real deep-cycle battery can last 10 years if one is careful, our longest running leisure battery finally keeled over completely after months on its last legs at 6 years old (made by FIAM). The two blue Exide leisure batteries both died after less than 3 years, one due to using with an inverter too powerful, one due to long term overcharging.
Nickel-Iron is a much more long-lived technology - though it costs 4 times more for the same storage/power output. There are nickel-iron batteries in use for off-grid solar that are 80 years old, restored to reasonable capabilities simply by rinsing the plates and then replacing the potassium hydroxide electrolyte. New ones are still being manufactured in a few places, mainly China but also Russia and I have heard of someone in Hungary too. These batteries do not mind being discharged and left discharged like lead-acid does. They do not mind being overcharged and left charged like lithium-ion. They can be charged 4 times faster than lead-acid for the same storage capacity. Of course there are some disadvantages too, the main ones being high self-discharge and a low energy efficiency - only 65% compared to 80-90% for lead-acid but the advantages - in my opinion - far outweigh these. They cost more - but if they even manage what the manufacturers claim - 20 years to drop to 70% of their original capacity - then they serve far more than 4 lead-acid batteries simply because you can actually use their capacity. If you have to stop doing things because the sun doesn't come out and you can't be sure that it will come out tomorrow, that seriously limits the usefulness, effectively the capacity, of a lead-acid battery - and these do not have that limitation.
UPDATE: we have had Nickel-Iron batteries for a while now, but after about 10 months of drastic underperformance I have moved to a recycled lithium storage for our power. The Nickel-Iron set we got was 100Ah * 20 cells for a 24V system, and cost (including shipping and taxes) about €1300 2 years ago, manufactured by Chong. Ours was one of 3 separate systems of Ni-Fe cells that were bought at the time, another of the same size and one double that size. They started out bad and got worse, after about a year they were only storing about 16 amp-hours. Apparently we have to 'Cook' them a few times, by giving them a 2.5-times continuous overcharge at C5 rate 3 to 5 times, but since our solar panels and regulators are not able to sustain a high enough current and voltage to do this, our NiFe cells now sit idle. The other two systems (who both did the cooking by connecting their panels direct with no regulation and just leaving them connected for a week or two while they went away) have had some improvement of battery performance, but to a level similar to when they arrived - capacity of about 50% what they were rated, and strong power limitations, that high power devices only work when the batteries are full and the panels are supplying significant power.
Owing to the insufficiency and cost of the Nickel-Iron batteries, instead of spending thousands more on NiFe, and needing something that would work, and not wanting to spend more on Lead-Acid which feels like just a money-hole due to short lifespans and the impossibility of keeping them charged when the needs of a community are applied to them, I decided to build a Lithium-Ion battery out of laptop-recovered 18650 cells. With a cost of €350 I now have 8kWh (7s144p) that actually works, supplies power over the dark times and doesn't mind staying empty for a time. It remains to be seen how long they last though, since lithium cells have quite a limited cycle-life - but since they only really get discharged a few times a year and I have the top voltages (where most of the degradation happens) closed off, they might last much longer than a typical laptop battery would. I have documented my build on secondlifestorage.com
<:END UPDATE: now back to talking about lead-acid batteries...
Although I do not recommend doing this, especially with an expensive lead-acid battery, charge regulators are optional. What they do is: 1) limit or stop the current coming into the battery when it is full; 2) get the most out of your panel when the battery is being or has been discharged. The reasons for (1) are from the battery getting damaged by overcharging. Once charged, a battery starts to turn its water into hydroxy gas which bubbles out and needs to be replaced. I have yet to refill a leisure or starter battery successfully, dirt always gets in and the battery then self discharges. The reason for (2) is the mismatch between the panels Maximum Power Point Voltage and the batteries voltage. A 12V rated panel may produce best at 16 volts, at any voltage less than that its power output is reduced proportionally. Connecting it strait to a battery at 13V you lose 3/16ths of the panels possible output, and a good regulator (not all regulators do this, mind) will step down the extra voltage into extra current at the batteries voltage. Even better regulators will notice that the MPPV changes at different light levels and track the most appropriate voltage to operate at for your panels at this time (sunlight and panel temperature both affect the best operating point). This is called Max Power Point Tracking.
For the electronically creative among you I will be publishing for free simple and effective MPPT charge regulator designs for charging 12V batteries from 15V and 30V panels in the near future (as soon as I have built and tested them myself). Component costs will range from €15 for a 16A regulator to €30 for a 60A regulator that will charge a 12V battery from 3 235W 30V panels.
UPDATE: A simple 40A solar charger/regulator that could charge batteries from solar panels with open-circuit voltage up to 40V can be made for about £20. It is based on a commonly available CC-CV buck regulator module ( this one ) which is about £10. It can be upgraded with higher power components for about £8, to operate reliably at 40A output, and converted to a solar regulator by adding a few components to make it maintain a minimum input voltage (reducing output to maintain this). Details will be on my projects page. <: END UPDATE.
Another option to connect to a 30V panel is a 24V battery (2 same type 12V batteries with ones + connected to the others minus) but this then requires all 24V gear 24V PSU's for phone and laptop and a 24V version inverter. These are all made for truckers. Trucks use 24V because it makes wiring a long vehicle easier. Doubling the voltage quarters the wiring loss for the same length of the same wire carrying the same power (e.g. a 12W tail-light or 5W indicator).
Cables are important - without them nothing happens. If you use cables that are too small for the current they will carry then they'll get hot, wasting power and potentially melting, causing short-circuits or even fires. Just because a certain wire would be able to deal with a certain appliance at 240VAC means nothing at 12VDC. The difference is between power and current. The same device (for example a 240W lamp) would use 1Amp at 240V but 20A at 12V. It is the Amps that generate heat in the wire, not the power of the appliance - the wire you use must be rated for the current that it will carry at 12V or 24V. I use at least 2.5mm² for lower power connections (up to 10A, 120W) and keep them shorter than 3m long if possible, with appropriate fuses close to the battery. Longer runs need fatter wires or they loose excessive amounts of voltage - for example a laptop DC power supply will not run a laptop at the other end of a 15m cable-run of 2.5mm² wire. Inverters usually come with appropriate wires, like 50mm² and 0.5m long for 3000W. Do not extend an inverters low-voltage wires, and attach direct to the battery terminal - the inverter should have fuses in it.
Inverters turn 12v or 24v DC from a battery into an approximation of mains power. I have rarely met anything that doesn't work with the cheaper modified sine type of inverter, the one exception being a 2000W angle-grinder that had a soft-start circuit that wouldn't start - and (according to their sales people) the current model Makita Electric chainsaws. Speed controllers in tools and kitchen appliances can be strained by the square waves too, but I've only had one actually blow and that was one I'd taken out of the jigsaw it was meant for and fitted it to a 4-way socket that I wanted to run other tools from that didn't have a speed controller, and probably broke because of over-loading. Power supplies for other things work fine but can buzz, due to the square waves slapping against the components. When choosing an inverter, the power rating should be 50% more than the rated power of your largest tool. This is to cover startup surges and high load usage/stalls. Inverters can be noisy, especially the smaller ones, with fans constantly running. They also consume a small continuous amount of power when on (the larger the inverter the more power it takes for itself as a rule), even when there's nothing plugged into them or turned on.
For things that will be ongoing for some time like laptops, I suggest using direct 12V power supplies which are silent and have less overhead - if you can be close to your battery. For music I recommend an mp3 player which can be recharged from 12volt connected to a good quality car amp and good hi-fi speakers, or if you're not an audiophile many PC speakers have mini amplifiers built into them and can be run direct from 12VDC. The limitation of connecting PC speakers to the battery direct is that if you plug the laptop in via a 12V laptop PSU to the same battery then there is a huge amount of noise from earth loop voltages - as long as the signal source has its own battery it works fine though. I had my entire recording studio set up to run from DC without an inverter (the noise would have been intolerable) by winding extra outputs from the car-amp's internal power supply transformer. These fed the mixer and the Yamaha keyboard isolated outputs so there were no earth loops or interference, even running the laptop from its power supply from the same 12V battery. The mixer, keyboard and amp (not loud) took about 2.5 amps (30W) total to run, and with my new laptop and the new batteries I would have been able to work for many hours overnight without worrying. A DC setup is also free from the hums and noise of an AC setup. The first time I plugged my Yamaha AN1x direct to a 12V battery and turned it on I thought it was broken - the familiar hiss failed to appear in my headphones even at max volume. You can touch the tip of the amplifier's signal wire and all you get is a very distant crackle from a thunderstorm happening 100 miles away - try that in a city and you'll be deafened by the AC mains being picked up by your body - and the same applies with inverters too.
Last time I checked, (late 2011), there was a massive price discrepancy between UK and the rest of Europe on solar panels. we got ours in Germany, though there is now a supplier nearer to us at similar prices. The difference was about 40% to 100% for the 30V panels and the price per watt doubled again for 12V panels. This doubled also in Europe - 12V solar is a niche market. Grid attach systems work up to a 600V total from 20 panels and then you put another 20 in parallel if you want (you get 20 on a pallet). Prices at that time worked out to about €1 per watt of peak power, and have now approximately halved again to 0.52 €/W (including tax).
A 29 to 30volt output at 7.6 to 8 amps is standard, banded into 220W, 230W, 240W, 250W and priced per watt accordingly. look for a local installer who might be able to sell a single panel - wholesalers only normally deal in pallets of 20.
Most panels are now coming from China. I've gone for poly-christalline, though I looked also at mono-christaline at similar but higher prices but different dimensions both physically and electrically. I expect them to still be working in 100 years time - they are guaranteed for 30 years. Amorphous type panels can be cheaper but I think their lifespan is much shorter (the two small ones we had degraded to unusable in less than 5 years) and they are larger for the power output.
The other key investment is the battery. Until recently I didn't know there was a real choice of battery technology but recently I have become aware of Nickel-Iron batteries as a viable if expensive alternative to lead-acid.
If you are going to buy a lead-acid type battery, I recommend getting a true deep cycle 'Golf-Cart' battery rather than any kind of leisure battery, though we did get a reasonable one 2 years ago, which did about 30% of its 101Ah(Amp-Hour) rating at low power and 120A for 5 mins (it was rated to start a vehicle at 680A). Our battery is a 240Ah golf-cart type. It can do at least 2 complete wash cycles (heater disconnected) and still be only half discharged and still capable of 100A for the spin at the end of that, and I have pushed it to 200A for 1/2 an hour with the chainsaw. It cost us 400€ in a local battery shop in Riverolo, weighs about 70KG and is 2 6-volt batteries linked together with an extra cable. You can probably find a 120Ah true deep cycle of 12V that will be plenty for your needs (don't use more than 1000W inverter with that). If you had a smaller panel, then the Ah deficit per day at 15% will accumulate. The battery will suffer if over-discharged (below 11.6V) or if left mostly discharged for more than a night. In one week, last year, the above mentioned 'good' leisure battery lost about 25% of its capacity (it had hardly degraded at all in the year before that) when we had a dark week and had discharged the battery at the beginning (this was before the new panels - we only had 3.5A at full sun, meaning just 0.35A between us all in that dark week). The other, older batteries were all pretty much ruined by that week and have all failed completely since then. The chemistry of lead-acid batteries forms lead sulphate in a reversible way as it is discharged. The lead sulphate, though, if left for a while (like a few days), changes to a different form which cannot then be split by the charging current, and battery storage capacity(Ah) and current (amps) ability is lost. If you use lead-acid, batteries are a consumable ongoing cost of off-grid solar. Making them last and requiring less storage is the reason for the large size of panel I suggest. A real deep-cycle battery can last 10 years if one is careful, our longest running leisure battery finally keeled over completely after months on its last legs at 6 years old (made by FIAM). The two blue Exide leisure batteries both died after less than 3 years, one due to using with an inverter too powerful, one due to long term overcharging.
Nickel-Iron is a much more long-lived technology - though it costs 4 times more for the same storage/power output. There are nickel-iron batteries in use for off-grid solar that are 80 years old, restored to reasonable capabilities simply by rinsing the plates and then replacing the potassium hydroxide electrolyte. New ones are still being manufactured in a few places, mainly China but also Russia and I have heard of someone in Hungary too. These batteries do not mind being discharged and left discharged like lead-acid does. They do not mind being overcharged and left charged like lithium-ion. They can be charged 4 times faster than lead-acid for the same storage capacity. Of course there are some disadvantages too, the main ones being high self-discharge and a low energy efficiency - only 65% compared to 80-90% for lead-acid but the advantages - in my opinion - far outweigh these. They cost more - but if they even manage what the manufacturers claim - 20 years to drop to 70% of their original capacity - then they serve far more than 4 lead-acid batteries simply because you can actually use their capacity. If you have to stop doing things because the sun doesn't come out and you can't be sure that it will come out tomorrow, that seriously limits the usefulness, effectively the capacity, of a lead-acid battery - and these do not have that limitation.
UPDATE: we have had Nickel-Iron batteries for a while now, but after about 10 months of drastic underperformance I have moved to a recycled lithium storage for our power. The Nickel-Iron set we got was 100Ah * 20 cells for a 24V system, and cost (including shipping and taxes) about €1300 2 years ago, manufactured by Chong. Ours was one of 3 separate systems of Ni-Fe cells that were bought at the time, another of the same size and one double that size. They started out bad and got worse, after about a year they were only storing about 16 amp-hours. Apparently we have to 'Cook' them a few times, by giving them a 2.5-times continuous overcharge at C5 rate 3 to 5 times, but since our solar panels and regulators are not able to sustain a high enough current and voltage to do this, our NiFe cells now sit idle. The other two systems (who both did the cooking by connecting their panels direct with no regulation and just leaving them connected for a week or two while they went away) have had some improvement of battery performance, but to a level similar to when they arrived - capacity of about 50% what they were rated, and strong power limitations, that high power devices only work when the batteries are full and the panels are supplying significant power.
Owing to the insufficiency and cost of the Nickel-Iron batteries, instead of spending thousands more on NiFe, and needing something that would work, and not wanting to spend more on Lead-Acid which feels like just a money-hole due to short lifespans and the impossibility of keeping them charged when the needs of a community are applied to them, I decided to build a Lithium-Ion battery out of laptop-recovered 18650 cells. With a cost of €350 I now have 8kWh (7s144p) that actually works, supplies power over the dark times and doesn't mind staying empty for a time. It remains to be seen how long they last though, since lithium cells have quite a limited cycle-life - but since they only really get discharged a few times a year and I have the top voltages (where most of the degradation happens) closed off, they might last much longer than a typical laptop battery would. I have documented my build on secondlifestorage.com
<:END UPDATE: now back to talking about lead-acid batteries...
Although I do not recommend doing this, especially with an expensive lead-acid battery, charge regulators are optional. What they do is: 1) limit or stop the current coming into the battery when it is full; 2) get the most out of your panel when the battery is being or has been discharged. The reasons for (1) are from the battery getting damaged by overcharging. Once charged, a battery starts to turn its water into hydroxy gas which bubbles out and needs to be replaced. I have yet to refill a leisure or starter battery successfully, dirt always gets in and the battery then self discharges. The reason for (2) is the mismatch between the panels Maximum Power Point Voltage and the batteries voltage. A 12V rated panel may produce best at 16 volts, at any voltage less than that its power output is reduced proportionally. Connecting it strait to a battery at 13V you lose 3/16ths of the panels possible output, and a good regulator (not all regulators do this, mind) will step down the extra voltage into extra current at the batteries voltage. Even better regulators will notice that the MPPV changes at different light levels and track the most appropriate voltage to operate at for your panels at this time (sunlight and panel temperature both affect the best operating point). This is called Max Power Point Tracking.
For the electronically creative among you I will be publishing for free simple and effective MPPT charge regulator designs for charging 12V batteries from 15V and 30V panels in the near future (as soon as I have built and tested them myself). Component costs will range from €15 for a 16A regulator to €30 for a 60A regulator that will charge a 12V battery from 3 235W 30V panels.
UPDATE: A simple 40A solar charger/regulator that could charge batteries from solar panels with open-circuit voltage up to 40V can be made for about £20. It is based on a commonly available CC-CV buck regulator module ( this one ) which is about £10. It can be upgraded with higher power components for about £8, to operate reliably at 40A output, and converted to a solar regulator by adding a few components to make it maintain a minimum input voltage (reducing output to maintain this). Details will be on my projects page. <: END UPDATE.
Another option to connect to a 30V panel is a 24V battery (2 same type 12V batteries with ones + connected to the others minus) but this then requires all 24V gear 24V PSU's for phone and laptop and a 24V version inverter. These are all made for truckers. Trucks use 24V because it makes wiring a long vehicle easier. Doubling the voltage quarters the wiring loss for the same length of the same wire carrying the same power (e.g. a 12W tail-light or 5W indicator).
Cables are important - without them nothing happens. If you use cables that are too small for the current they will carry then they'll get hot, wasting power and potentially melting, causing short-circuits or even fires. Just because a certain wire would be able to deal with a certain appliance at 240VAC means nothing at 12VDC. The difference is between power and current. The same device (for example a 240W lamp) would use 1Amp at 240V but 20A at 12V. It is the Amps that generate heat in the wire, not the power of the appliance - the wire you use must be rated for the current that it will carry at 12V or 24V. I use at least 2.5mm² for lower power connections (up to 10A, 120W) and keep them shorter than 3m long if possible, with appropriate fuses close to the battery. Longer runs need fatter wires or they loose excessive amounts of voltage - for example a laptop DC power supply will not run a laptop at the other end of a 15m cable-run of 2.5mm² wire. Inverters usually come with appropriate wires, like 50mm² and 0.5m long for 3000W. Do not extend an inverters low-voltage wires, and attach direct to the battery terminal - the inverter should have fuses in it.
Inverters turn 12v or 24v DC from a battery into an approximation of mains power. I have rarely met anything that doesn't work with the cheaper modified sine type of inverter, the one exception being a 2000W angle-grinder that had a soft-start circuit that wouldn't start - and (according to their sales people) the current model Makita Electric chainsaws. Speed controllers in tools and kitchen appliances can be strained by the square waves too, but I've only had one actually blow and that was one I'd taken out of the jigsaw it was meant for and fitted it to a 4-way socket that I wanted to run other tools from that didn't have a speed controller, and probably broke because of over-loading. Power supplies for other things work fine but can buzz, due to the square waves slapping against the components. When choosing an inverter, the power rating should be 50% more than the rated power of your largest tool. This is to cover startup surges and high load usage/stalls. Inverters can be noisy, especially the smaller ones, with fans constantly running. They also consume a small continuous amount of power when on (the larger the inverter the more power it takes for itself as a rule), even when there's nothing plugged into them or turned on.
For things that will be ongoing for some time like laptops, I suggest using direct 12V power supplies which are silent and have less overhead - if you can be close to your battery. For music I recommend an mp3 player which can be recharged from 12volt connected to a good quality car amp and good hi-fi speakers, or if you're not an audiophile many PC speakers have mini amplifiers built into them and can be run direct from 12VDC. The limitation of connecting PC speakers to the battery direct is that if you plug the laptop in via a 12V laptop PSU to the same battery then there is a huge amount of noise from earth loop voltages - as long as the signal source has its own battery it works fine though. I had my entire recording studio set up to run from DC without an inverter (the noise would have been intolerable) by winding extra outputs from the car-amp's internal power supply transformer. These fed the mixer and the Yamaha keyboard isolated outputs so there were no earth loops or interference, even running the laptop from its power supply from the same 12V battery. The mixer, keyboard and amp (not loud) took about 2.5 amps (30W) total to run, and with my new laptop and the new batteries I would have been able to work for many hours overnight without worrying. A DC setup is also free from the hums and noise of an AC setup. The first time I plugged my Yamaha AN1x direct to a 12V battery and turned it on I thought it was broken - the familiar hiss failed to appear in my headphones even at max volume. You can touch the tip of the amplifier's signal wire and all you get is a very distant crackle from a thunderstorm happening 100 miles away - try that in a city and you'll be deafened by the AC mains being picked up by your body - and the same applies with inverters too.