Hi Shonky,shonky wrote:Hi, all.
Errata in previous posts- should have typed 6B&S cable, not 6mm.
No comments on reef knots and Rescue Tape instead of soldering or MP4 connectors? Hope the readers are in silent agreement not equally silent disgust.. The nice salesman at the camping show states that one turn of this tape will insulate 8000volts if applied correctly.
Craig - the fridge is 12v, not three way, and has a new exhaust fan, new 6B&S cabling straight to the battery, and i just fitted a large intake vent to it, all of which made no difference atall.
The fridge uses daily 3.5x24 = 84amps
The Imac uses 6x4 =24amps
Lighting about 4amps
equals 116 amps on a big day.
In good sun we should obtain 22amps from the roof panels,say for 6 hours max = 132amps, and in all seasons 8amps for 8 hours =64amps, from the folder, we hope. With some output from the roof panels this should give us between 64 and 200amps. Obviously we're more frugal with the computer's use and the fridge setting during inclement weather.
Craig, I know this is looking like a third battery is called for, but the point of my discussion is that folding panels have a definite use when the sun is not overhead. If you can gaze at the sun without tilting your head backwards fixed panels will not reach their maximum output.
I had the same problems with my solar, and have been working through it, I have a similar set up to you in that I have a 12v compressor fridge, but have 520w of solar, The way I see your problem is, You state that You have 22 amps available for six hours,
firstly, even in Darwin at this time of year the tables rate 5 1/2 hours of usable sunlight maximum, they do not rate the solar input until the light levels reach a certain irradiation level.
Secondly, even though you have 22 amps maximum once the batteries reach bulk charge limit (14.5 -14.7 V depending on the charging regime of the charger) then the amps will drop rather drastically, In my case from nearer 30A to less than 10 (usually around 2 o'clock) until the batteries reach float voltage, the other problem is that the fridge will cycle on and draw nearer 7 A so during the peak charging times, at these times, instead of getting 22A in you are only getting 15A.
All these factors combined lead to problems with solar charging lead acid batteries, the major one being that the batteries need to be at maximum charge (14.5V) by midday, so that the charger has time to go through its charging regime before the sun goes down. So to replace an overnight use of 50AH you require 25AH input in 2.5hours which is 10A plus 7A fridge draw results in a 17A or around 250W of panel but allowing for the losses in the system occasional cloud over the sun etc. you really require 500w solar array or double what the pundits say.
These are my figures and no doubt a lot of people will tell me I am wrong, and that they achieve the same charging rates from a 250w array and maybe they do, but I have been unable to do so consistently parked up anywhere in Australia, without any external power.
Another problem that arises is that every day your/My batteries are not being fully charged the losses accumulate so that while the solar may charge to 90% SOC the first day the following day it will be less so that after a week or so the batteries are down to 75% or less, the further you get behind the more power is required to overcome the discrepancies, which is another reason I advocate doubling the solar requirements.
