mahnamahna wrote:Smooth, Please excuse my ignorance, like others here Electricity is a dark art. If the solar panels I am looking to import work out (being tested at the moment) they are so cheap, and I have so much roof real estate, that I am going to put 6 x 180 watt panels up there. Am I better off joining them up there and sending all that load down one big cable or sending each panels wiring down individually and then joining them just before the regulator. Sending over 1000 watts @ 18v down one wire, isnt that about 60 amps and is that wire going to be as thick as say and power extension cord? Or will it be thicker than that? The wires that come out of the panels now are about that thickness so sending 6 of them down will need either multiple routes or a really big conduit.
Or is 1kw just going to be way over powered? The way my uneducated mind thinks, is that if I can put them up there then I am not likely to ever exceed their feed, in usage. Does it work that way. Am thinking on having 400amp hour lifepo4 battery bank, maybe 600AH (but cant afford the extra 200AH yet). Will have outboards so they only charge at 15amps. Will probably have one of those Honda 2000 petrol gennies for emergencies or for when we want to use the convection microwave to roast. I have a 200 litre Isotherm fridge/freezer not sure what it draws yet, it depends on ambient temp I think but it has a danfoss 50 compressor which I believe are pretty good, I will have the usual array of electronics including radar, plotter, sounder and ais, 19in lcd tv with dvd player, laptops (cant imagine life without internet!), led lighting throughout, and will be buying a watermaker, probably an 80e Katydyn, makes about 12 litres an hour and uses about 8amps an hour. Will probably want to run that every second day.
For that size array, you should get an MPPT charge controller. I have an Outback Flexmax 80. You can then wire your solar panels in series - ie positive to negative - so then you increase the voltage, but the current "upstream" of the charge controller will stay the same as if you only had one panel.
The charge controller will step that down to the battery voltage and the current will multiply. So you only need heavy gauge wire between the charge controller and the batteries.
This also has the bonus effect of improving yeild in poor conditions. ie, if you had low light and each panel could only manage about 11 volts - in parralel you'd get no charge - 11 volts won't charge 12 volt batteries. But in series there would be 66 volts, which the charge controller can reduce to battery voltage, and produce a little current.
IMO you can't have too much solar. In good sunlight your batteries might be fully charged well before lunchtime, but when it's crappy (like it is in Sydney now) you want every Watt you can get.