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Old 02-02-2011, 20:04   #46
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Originally Posted by Southern Star View Post
Velma, Watts divided by Volts will give you AMPs. Hence, with a 12 V system, panels totallying 360 Watts can theroretically produce 30 Amp/hrs of charge. Theoretically because: 1. Your panels cannot be shaded. 2. these figures are calculated with the sun at an optimal angle (essentially, 4 or perhaps 5 hours mid-day). 3. the panels must be angled perfectly into the sun at all times. 4. There are internal losses through regulation,
And last while definitely not least:

12 Volt panels are neither delivering 12 Volt nor are they rated at 12 Volt hence 360 Watt / say 17 Volt = say theoretically 21 (!!!) Amp.

20 Not 30!

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Old 02-02-2011, 20:12   #47
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Originally Posted by Southern Star View Post
Thanks Mark for the clarification. My results with 240 watts (3 X 80 Watt Kyocera panels mounted between the davits and essentially unshaded) run about 45 to 70 A/H depending upon the amount of sunlight. I am going to add 2 more 100 Watt panels, but as these will be mounted on the bimini, they will be much more susceptible to shade and hence less effective. Still, not bad for something reliable, silent and relatively cheap.
Do you mean amps per day, rather than A/H? With 260 watts (2 X 130 Sunsei panels mounted flat as a solar bimini) I reliably charge 90 amps per day, averaging around 16 A/H usually during peak hours.
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Old 02-02-2011, 20:58   #48
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I have 3 X 200 watt mono solar panels and the BEST I ever see is 22amp/hr combined during 5 hours a day.
mounted flat/no shade
I expected more output.
i have a good regulator.
Before i buy another panel where should i look to get increased output, or is this output considered normal for 30 degree celsius sunny tropical days in brisbane Qld..
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Old 02-02-2011, 22:08   #49
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beau... why only 5 hours a day? are you using a lot of power out of your batteries or a little? if your regulator is on float most of the time, then the regulator WILL NOT allow too many amps to go through it, because the batteries simply wont accept it if they are mostly fully charged most of the time. with 600 watts of solar panels 600 divided by 12= 50 amps registering on your regulator if the conditions are perfect and your batteries are low enough to accept this power....and a sliding scale (downhill) either side of that. 600 divided by 4.5 = 133 amps per day on a year round average.... and i`m in australia too.... thats if you operate on 12 volts
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Old 02-02-2011, 22:29   #50
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Thank you "budgie smuggler"
I have a 600 amp/hr AGM battery bank.
I realise I probably use a fair bit of power.
I have a 120 liter 240 volt fridge and a 240 volt freezer as well,running through a 3,000watt inverter.
But that is what we like on a boat. (ice for sundowners)

I also have a 2kva Kipor generator.(backup)

I just "assumed" 600 watts of solar would be enough on a good day.
Tomorrow I will check my wiring, something is wrong I just don't know where,yet.?
Thank you for your help.
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Old 03-02-2011, 00:57   #51
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beau... those 240volt items that you use will draw an awful lot of power from a 12volt system. if you check the watts of your 240 volt fridge (it will be on a plate somewhere) and divide that wattage by 12 (12 volt) you will see how many amps per hour that appliance is using. i.e. a 2400 watt electric kettle 2400 / 12 = 200 amps per hour !!!!!! luckily it`s only on for 2 or three minutes to boil water, but do the sums...it`s scary. also the 3000watt inverter alone will draw a minimum of 2 amps per hour before even connecting anything to it. i have 330 watts of solar panel & 400 amps of battery 330/4.5 = 73 amps per day on ave coming in.. my engel 40 ltr 12 volt fridge draws 25 amps per day set on fridge..as a freezer it uses 50 amps per day. i have a espresso coffee machine which is 1200 watts 240 volt.. 1200/12= 100 amps per hour. it takes two minutes to make a short black coffee.. again do the sums.. i allow 5 amps per cup of coffee.......big trouble, i drink 10 cups a day ....that`s 50 amps for coffees.... does`nt leave me any leaway for anything else. i have one of those el cheapo chinese copies of a copy, of a copy, of a copy little generators and i use it solely for charging purposes. i connect a 50 amp battery charger to the gen. if the little gen would take it, i`d connect a 100 amp battery charger to it... but alas, it would blow the generator into very small particles.. never to work again. also when you work out the amps per day that you draw, then you will need to put back in +20% back into the battery.... on your system check that the wires from the solar panels are heavy enough. if they get at all ,even warm, you will lose heaps of amps to heat. in your case the wire could have 60 amps going through it.... that`s an awful lot of power
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Old 03-02-2011, 06:23   #52
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Sorry Bash, I did mean total amps/day. My figures were for average days up here in Ontario, Canada, including ones with significant cloud cover. In my experience in California, you are getting much more sunshine. Nevertheless, even in direct sunlight at mid-day, it is rare for my panels to be producing more than 12 A/H.

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Old 03-02-2011, 06:36   #53
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Quote:
Originally Posted by Bash View Post
Do you mean amps per day, rather than A/H? With 260 watts (2 X 130 Sunsei panels mounted flat as a solar bimini) I reliably charge 90 amps per day, averaging around 16 A/H usually during peak hours.
Things are getting a bit confusing and the wrong way round here.
The instantaneous current is Amps.
Therefore someone might say my solar panels were producing 16 Amps at midday.

The cumulative amount of current is Amp Hours
Therefore someone might say today my solar panels put in 90 Amp hours today.
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Old 03-02-2011, 10:29   #54
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Originally Posted by noelex 77 View Post
Things are getting a bit confusing and the wrong way round here.
The instantaneous current is Amps.
Therefore someone might say my solar panels were producing 16 Amps at midday.

The cumulative amount of current is Amp Hours
Therefore someone might say today my solar panels put in 90 Amp hours today.

Thx Noelex, this was exactly what I was going to say. Another confusion area is the difference beetween AC (alternative current) and DC (direct current) Someone believed that his espresso machine was drawing 100 A.. The espresso machine works on 220 AC, hence, it draws 1400/220= 6,4 A. If the machine is 110 V, then it will be 13 A, not a 100 A.
On the other hand, 100 A is a terrible intensity; to carry it one would need a cable thick as yr forearm..

Cheers

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Old 03-02-2011, 10:40   #55
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Thanks Noelex - I knew that at one time (and will probably forget again) - lol.

Brad
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Old 03-02-2011, 10:46   #56
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Quote:
Things are getting a bit confusing and the wrong way round here.
The instantaneous current is Amps.
Therefore someone might say my solar panels were producing 16 Amps at midday.

The cumulative amount of current is Amp Hours
Therefore someone might say today my solar panels put in 90 Amp hours today.
Amps is the instantaneous current
Amp/Hours is amps integrated over time, normalised to one hour,
Amps per day ( or any time period), is a measure of the total amps generated or consumed ( well not really) in that time period.

Quote:
And last while definitely not least:

12 Volt panels are neither delivering 12 Volt nor are they rated at 12 Volt hence 360 Watt / say 17 Volt = say theoretically 21 (!!!) Amp.

20 Not 30!

Cheers,
barnie
Well yes and no, using a MPPT controller or any controller that matches input resistance, then the full power transfer is available. Hence a 360W panel can deliver 360/12 amps into a 12v battery. ( more or less)

Quote:
Someone believed that his espresso machine was drawing 100 A
he is correct , he was refering to what it would draw through a 12 v invertor from a battery.

Quote:
those 240volt items that you use will draw an awful lot of power from a 12volt system. if you check the watts of your 240 volt fridge (it will be on a plate somewhere) and divide that wattage by 12 (12 volt) you will see how many amps per hour that appliance is using. i.e. a 2400 watt electric kettle 2400 / 12 = 200 amps per hour !!!!!! luckily it`s only on for 2 or three minutes to boil water, but do the sums...it`s scary.
Actually its not scary at all and theres a very good set of articles on the Victron site where he goes into cooking by invertor.

my kettle ( 230V) is 1200 watts, it takes 120 seconds to boil with it 80% full ( about two pints) thats 3.3 amp hours to boil a kettle. thats easily replaceable

My stove has a 1300watt and a 900 watt ring, cooking pasta takes 10 minutes approx thats 12.5 amp hours. easily replaced by solar givng that i cook pasta once a day.

all assuming 12v systems and 100% efficiency.

Its the small stuff that runs all day thats the problem.

Dave
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Old 03-02-2011, 11:07   #57
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Originally Posted by goboatingnow View Post
Amps is the instantaneous current
Amp/Hours is amps integrated over time, normalised to one hour,
Amps per day ( or any time period), is a measure of the total amps generated or consumed ( well not really) in that time period.
I don’t want to get pedantic, we are after all yachtsmen not electronic engineers, but some of the posts become very confusing when everyone is using different terms.

Amp hours is not normalized over one hour, or any time period.

I could say my solar panels produce 90 amp hours a day or 630 amp hours per week or 32850 amp hours per year or….. well you get the picture.
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Old 03-02-2011, 11:19   #58
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removed it, pedantic discussion

Dave
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Old 03-02-2011, 12:55   #59
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Originally Posted by beau View Post
I have 3 X 200 watt mono solar panels and the BEST I ever see is 22amp/hr combined during 5 hours a day.
mounted flat/no shade
I expected more output.
i have a good regulator.
Before i buy another panel where should i look to get increased output, or is this output considered normal for 30 degree celsius sunny tropical days in brisbane Qld..
Not sure if you mean 22 amp/hours per day, or a peak of 22 amps for 5 hours in a day, = around 100 amp/hours....

But either way, that's low for a 600 Watt array.

Do you have an MPPT charge controller?

I have 600 Watts, 6 panels wired in series through an Outback Flexmax 80 MPPT.

On a (rare) sunny day in the Gold coast this January, we'd collect around 200-220 amp/hours, with peak amps being well over 40.
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Old 03-02-2011, 13:41   #60
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Amp/Hours = amps X hours, (at that exact number of amps). It is very simple.

!0 A/H = 1A for 10 hours or 10A for 1 hour...

My "340 AH" battery bank could theoretically provide (1A for 340 hours), (34A for 10 hours) or (340A for 1 hour) That is the theory anyway. In reality the first two examples might come close, the third not so close, because batteries don't live up to their potental if hit that hard, But you get the picture.

With a smart battery monitor like my Link 10, it has an "A" button. That tells me perhaps -5, which means that at that second, 5 more amps were going out of my batteries, (the load), than going in, (a charge device like solar).

Then if I hit the "A/H" button, and it says -35. That means to top off the batteries, I need to put back 35A for 1 hour, or 1A for 35 hours, or any combination that adds up to 35A/H.

Mark
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