Cable sizes are in cross sectional area that is the area of the wire when cut thru and looking at the cut end as opposed to bolts whose sizes are given in diameter so a connector that has stamped on it 8 by 10 will have a bolt hole 8mm in diameter but the hole for the cable although size 10 will be smaller.
Always use multi-core cable for all the d/c side of your system .The a/c side can be either single or multi-core .The current in a d/c circuit as in a high frequency system flows along the surface of a cable and so by having many pieces or wire inside one cable you increase the surface area it has to travel along and therefore reduce the loss of power transmitted through resistance , everything has a resistance which is robbing you of some of your power but you can reduce this to a minimum in many ways.
Do not skimp on cable sizes you will be using them for a long time and will regret it later.
Using a cable that is too small for the current will not only lose you power but could also heat up ( the result of too great a resistance in the cable) and is the cause of, many electrical fires in both the home and vehicles. The old electric bar fire is the best way to explain, it is just a height resistance wire wrapped around a ceramic tube, it is the resistance within the cable that causes it to heat up.
Do not use excessive bends in the cables.
Keep all cable runs to a minimum, so to position your panels or turbine as close as you can practicably manage to the position of the inverter , after this point it is not important as you have changed over to a/c and for all practical purposes there is no need to consider power loss as it is too small to worry about.
When connecting batteries either in series ( pos to neg ) or when using a bus bar always keep the cables in that part of the system the same length and type. If one of your batteries happens to be 4 feet from the bus bar and others are a few inches you should cut all the cables to the longest one in this case they would all need to be 4 feet long .
You can check for power loss thru your cables resistance by using a multimeter set to resistance but it will not be of a lot of help if you are unable to interpret the reading. A simpler way to do it that which we can all understand is to connect one end of the cables to a batteries and take a reading then take another at the unconnected end, the difference will be the loss thru resistance it terms of voltage. I have seen a system with up to 5 volts loss which is extreme and the reason for that particular systems failure to bring the batteries up to anywhere near full charge.
Try to keep to one colour for pos and another for neg throughout the d/c side and another 2 colours for the a/c.
Keep your wiring tidy it will do absolutely nothing as far as performance is concerned but it can save a lot of time later should you need to add, replace or do any work on the system and just as importantly help to avoid silly mistakes that we all make from time to time, as they can be costly in a circuit of this type as the components are as we all know firstly expensive and not at all forgiving.
I always send my underground cables through the black plastic water pipe that is readily available here , it is cheap and avoids you cutting into them later by accident as well as rodents chewing on them. I tie a couple of small nuts to some building line (I know it sounds painful doesn't it ) then take the pipe up a hill and feed it thru , to help it along you can run some water down the pipe at the same time , it works well .As soon as you have it out the other end tie some nylon string to it and pull that thru then the cables to that and repeat the process.
Be prepared to see a spark when you make connections depending on the size of the system and whether or not the panels are covered. This can be just a tiny spark or a great big crack sound, don’t panic as long as you have checked and double checked before making the connection that it is correct then you will only be getting what I would expect, it is simply as in a spark plug the current, trying to get to earth and jumping the last air gap before actually touching the connector, the more amps in the line the bigger a gap will be jumped with the resulting spark much bigger and louder.
You will need an earth in the system which you take from the neutral side of the system via a 10mm cable to an earth rod, I normally recommend a 2mtr length buried horizontally 80cm below ground, or if the ground is soft enough you can hammer it in at a 45 degree angle and make it a bit shorter. Do not use the same earth rod for the turbines they need there own, as well as the turbine the steel pole upon which it is mounted also needs to be connected to the earth rod.
If you wire your system via a bus bar you can take the earth from this point.
Switches and fuses should be either a/c or d/c they are not the same and using a switch too small for the job could leave you not being able to switch off as the current is well capable of welding the contacts within the switch to leave it permanently in the on position. I like the Spanish word for a switch ( interrupter ) it dose just what is says on the can, it interrupts the current flow.
CAVES