No. of Solar Panels.

Discussion about any electrical topic except 240 volts. Solar, converters, inverters, lights, battery chargers, etc
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John M
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Re: No. of Solar Panels.

Post by John M »

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.
Hi Shonky,
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.
"Recycled Teenagers", John, Shirley and Four legged person Beau, travelling in a 7m Isuzu bus towing a trailer. Enjoying the fellowship of the road
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T1 Terry
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Re: No. of Solar Panels.

Post by T1 Terry »

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.
My first comment would be regarding the connections, the tape may well insulate against a short circuit, but it doesn't garuntee a good connection. The current from solar panels is rather forceful, if it's a poor joint it will just make heat at the connection rather than attempt to push through and charge the battery and the voltage can climb to around 20vdc, that's a lot of push into a bad connection. The worse the joint the more current is wasted resulting in a drop off in voltage at the end of the cable yet a rise in voltage before the bad joint, this seems to be what you are saying is happening. Solar requires heavy cables, 6B&S will carry 30 amps @ 12v over 10 mtrs with little voltage drop, so the cable size is ok, very good joints are also required, I'll attach a photo of what happens in the joints aren't perfect.
House solar damage small.JPG
At first glance it looks like a dead short, yet the positive cables the same 8 B&S gauge (7mmsq) aren't damaged. This was caused by a dirty connection inside the brass link block, the resistance created enough heat to oxidise the copper wire, that increased the resistance creating more heat and oxidised copper has a lower melting point the copper in good condition, the cables melted. Twisting cables together instead of a good solder joint or crimped joiner is asking for trouble when solar is involved, a well performed wore wrap is suitable though, but you really do need to know how to perform a good wire wrap joint.

So, the first place I'd be looking is the voltage at the panel compared to the voltage at the solar regulator, each panel seperately, if the 2 voltages aren't the same when the system is under load, (charging the battery at the boost stage) a thorough inspection of all the cable and all the joints will be required till the problem joint or section of cable is located.
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shonky
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Re: No. of Solar Panels.

Post by shonky »

Hi,al

John M - your discourse is IMHO well presented and thoroughly informed. As your opinion, nay, statement of the facts, concurs with mine feel free to drop by our bus for free lamingtons at any time.
FYI at present, 1330 in sunny repeat sunny Qld our charging rate is 12.8v and input is 4amps. The fact that the Dometic is running, nullifying our solar input, is clear indication that we should switch on shore power. Experiments need only go so far.

T.I.Terry - your input is as welcome as always.The Rescue Tape will only be used on the folder for now at a max of 8amps and not inside the bus. All other connections were checked by an auto-sparkie and are fine. The performance of the folder will be carefully monitored and should it fail you will be advised accordingly. Sometime. You can have free lamingtons too.
My intention is to join the 6B&S cable to the folder as far along as possible, bypassing the little regulator and relying on the Morningstar 30amp solar controller.
See you on the back roads,
shonky et al.
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Re: No. of Solar Panels.

Post by T1 Terry »

Hi Shonky, I miss understood where the rescue tape was going to be used.
Still a little confussed at this end
FYI at present, 1330 in sunny repeat sunny Qld our charging rate is 12.8v and input is 4amps. The fact that the Dometic is running, nullifying our solar input, is clear indication that we should switch on shore power. Experiments need only go so far.
Is the 4 amps what is coming into the battery or what is coming in from the panels? Just trying work out if the 4 amps is what is left after the loads are supplied. How many and what capacity solar panels are connected to the Morningstar at the moment?
A person may fail many times, they only become a failure when they blame someone else John Burrows
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shonky
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Re: No. of Solar Panels.

Post by shonky »

Hi, all.

T.I.Terry - at present we have 2x135w and 1x140w panels on the roof, and the 4amps are coming from the solar via the controller to the battery. The controller is not set up to display loads as the cost of doing so would apparently be prohibitive, whereas our battery charger displays load amps when connected to external power.
See you on the back roads,
shonky et al.
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BruceS
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Re: No. of Solar Panels.

Post by BruceS »

Shonky I have some info as well but as I;'m diabetic & I'm told your lamingtons are very sweet, (thanks to Mrs Shonky) I'll not bother you with it for now.
If ever you're in my area feel free to drop in and chew bark off trees and indulge in other boring fibre related luxuries!!!
PS: dark cooking chocolate is NOT sweet & can be eaten!

(I do think your panels are not doing their job as they should be or your batteries need a talking to!!)
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shonky
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Re: No. of Solar Panels.

Post by shonky »

Hi, all.

Ex-adminperson - good to hear from you. It will please you to learn that although we tanked up twice last month our plans are at present are to stay within a 20km radius till end August, thereby eking out the current tankful. We are also only heading to camps with shore power.
The panels can only be described as dormant for now, and considering the fridge draws direct from the batteries from 3pm to 10am the next day gives a drawdown of 76amps even before the big apple is turned on. If the eagerly awaited folder does not meet our expectations a third battery will be considered, although our $400 genset should be helpful. Should a third battery be of the same size as the other two? Heavy cables and all of the same length of course.

BTW Mrs shonky can turn out very small lamingtons..
See you on the back roads,
shonky et al.
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Re: No. of Solar Panels.

Post by BruceS »

Can you tell us make & model of your fridge please? Must be a pretty big one by the sounds of it.
How often does it cut in / cut out through the night?
My Civilian has 3 X 24V solar panels on it (190w) & is parked in a shed/garage & even with the roller door half way up I get some charge. Panels do not need direct sunlight at 90 degrees angle to work. OK to get absolute maximum they do but if you have 30% more panel than necessary you get away with a bit of dull weather & a bit of shading by trees etc.
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Re: No. of Solar Panels.

Post by TigerMK1 »

Have been away and recently revisited this thread. Having 7 panels on a 7Mr bus including a 4 seasons vent and the 2 big roof fans was a job. The result is still the same as before. The panels charge the LIPO battery pack. It feeds the inverter. It powers the F&P fridge. It also powers the satellite TV etc. The battery also feeds the led lights, the pump, the deisel heater and anything else I can think of. So far, even with crappy weather, on a good day, by 11am I am feeding the excess solar into the 240V hot water element. On a gloomy day, we use the gas for the hot water, the solar is busy with the fridge etc.
Still smiling, best investment ever made.
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Re: No. of Solar Panels.

Post by T1 Terry »

If you have 410w of solar and at 12.30pm in full sun you are only getting 4 amps, something is very wrong, a 120w panel will put more than that out laid flat at that time of day, mine on my patio roof do and they are cheap evilbay panels.
Each of my 250ltr Fisher & Paykel 240vac fridges powered through an inverter from 12v batteries only use 80 Ah in a 24hr period, something doesn't add up right at all.
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