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Old 03-02-2011, 17:25   #61
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Quote:
Originally Posted by Mark Johnson View Post

(...)

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

(...)
Elsewhere perhaps. But in battery charging and discharging NOT!

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Old 03-02-2011, 18:16   #62
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Barnie, No it is a useful tool... As I said it is theoretical. The SLOW A/H test should somewhat parallel a new batteries rating. It is the industry way of representing the storage capacity of a battery, before it goes flat. The battery A/H "rating" is more useful for "comparing" batteries than being exact, and it assumes a slow discharge!

For a very slow discharging test, however, the battery should come close to the number it is rated for. When a client ask me to tell him if his 100 amp/hour rated battery, is due for replacement, I put a 1 amp load on it, and start watching the load at about 60 hours. (In a perfect battery, it should run 100 hours) in theory. It never happens!

If it runs the load for 85 hours, I'd tell them it is "good enough". Even when I tested my brand new Trojans, (which had spent months on a shelf in a warehouse), they only achieved 90% of their rating. This is the industry standard. Also, sometimes the storage capacity goes UP after a new battery gets used a few times. This was true in my case. A few cycles and equalizes later, they tested out a bit better.

Still, this is a valid test, in fact it's the most valid there is, to know what the A/H of a battery REALLY is.

Now a 100A/H battery should also run a 50 amp load for two hours, but under these loads batteries never even come close to their rating. Then it is not a valid test...

This is why the test I do for my clients is a real world accurate measurement, not a close guess. (a 1 a load...)

Mark
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Old 03-02-2011, 18:27   #63
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Just a small thing Mark the symbol is Ah, not A/H which is a differnt thing altogether.

Dave
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Old 03-02-2011, 19:00   #64
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Thanks, I need to bone up on my symbols.. BTW my spelling is even worse!
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Old 03-02-2011, 19:18   #65
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i have been into solar power for umpteen years, have been there & done that and i still feel like a beginner when it comes to the sometimes "very technical" side of it.... what i would like to say to ANYONE who is even contemplating setting up a solar system for the very first time & does`nt know their watts from there amps...... GO FOR IT. even a 20 watt panel connected to a starter battery that no longer turns over the starter motor in your car will give you another year or two of service if used for LED lighting. ( without a monthly power bill as a bonus!! ) just remember that once hooked on solar power, it does become addictive (as you can see by all the posts) and adding ANOTHER panel is only just around the corner!!! .......... i need another short black espresso!!!... damn it...another 5 amps gone......
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Old 03-02-2011, 19:28   #66
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Quote:
Originally Posted by budgie smuggler View Post
i have been into solar power for umpteen years, have been there & done that and i still feel like a beginner when it comes to the sometimes "very technical" side of it.... what i would like to say to ANYONE who is even contemplating setting up a solar system for the very first time & does`nt know their watts from there amps...... GO FOR IT. even a 20 watt panel connected to a starter battery that no longer turns over the starter motor in your car will give you another year or two of service if used for LED lighting. ( without a monthly power bill as a bonus!! ) just remember that once hooked on solar power, it does become addictive (as you can see by all the posts) and adding ANOTHER panel is only just around the corner!!! .......... i need another short black espresso!!!... damn it...another 5 amps gone......
That's sooooo true!

Last time I told Wonderblond that I was planning to purchase another panel, before she assented to the purchase she asked, "Will this mean I get to use the inverter to make toast?"

Her point was well taken.
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Old 03-02-2011, 19:37   #67
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why did`nt i think of that..........A TOASTER............and another panel...........toast`l go well with my next coffee............ but my regulator/controller is only rated for 20 amps...........`spose a new regulator is out of the question................ A TOASTER....... new regulator...`nother panel....may need more batteries too......... who was it that talked me into solar???!!!!
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Old 03-02-2011, 19:50   #68
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the thought occured to me just a few weeks back... if i took down the mast and then covered every square inch of the whole boat with solar panels and run an electric motor....how simple would life be? BUT...... where would i put THAT NEXT PANEL ?
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Old 03-02-2011, 19:56   #69
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Data from a new system.

Hello All,

I've just installed my solar system and itís been operating for only about two weeks.
I have two arrays set up on my Catamaran:
- 4 x 75 watt (Shell) = 300 watts, and
- 2 x 235 watt (Kyocera) = 470 watts, giving a total of 770 watts.

They lie flat on the davit frame and the bimini. There are no issues with shade, (I've room for another 4 of the Kyocera's on the bimini, but that would be ostentatious.)

12 volt system, 860 Ah house batteries (Odessy AGM), two Morningstar 45 Amp MPPT controllers.

So far I've never been more than 130 Ah in the hole so the controllers are always throttling back what they can produce to protect the batteries.

I am in Marsh Harbour in the northern Bahamas swinging on the anchor.

Iíve never had less than about 100 Ah into the batteries even on cloudy days. On sunny days I get around 200 easily.

The peak current Iíve seen has been just over 42 amps (602 watts) out of the controllers when weíve run the fridge, freezer and inverter to power the ice maker and the vacuum cleaner, all at once.

I plan on testing the system in June, down south, at noon with 50% discharged batteries and a big load to see what these puppies can really produce.

regards, Ross
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Old 03-02-2011, 20:09   #70
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hang about olorin......vacumm cleaners, ice cream makers, ice makers...... fridges & freezers.....i`m still trying to get my head around the TOASTER !!!
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Old 03-02-2011, 20:22   #71
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For a toaster we use a wire rack held above the burner by spice tins. No need to run the inverter.
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Old 03-02-2011, 20:33   #72
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my grandmother made toast on her gas stove.. she had a wire rack that held thetoast just above the flame so the toast got a nice 'toasting' then flip and she cooked the other side...

I actually like the flavor of a 'burnt'/toasted toast.

also, grilled bread like for grilled cheese is kinda good too.
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Old 03-02-2011, 20:51   #73
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ok.... i`ll forget the toaster...... but golly gosh...... that icemaker sounds so nice. it`s about 43`centigrade here....... and i`m crazy enough to be drinking espressos!!....... joking aside, your system sounds like it will do the trick.. cats are so good for solar power,make the best of all that area for panels... the more, the merrier and not ostentatious. good luck with your system.
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Old 04-02-2011, 00:55   #74
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I didn't read every response, so if the math was covered I missed it.
Watts like horsepower is a unit of work P= I X E, just think of that tasty pie.
P (power in watts) = I (current in amps) X E (electromotive force volts)
So if you have an 80 watt panal producing 17 volts, figure on 4.7 amps.
That single panal for 9 hours of production is 720 watt/hr.
Run your 1100 watt microwave oven (@ 100% eff., which doesn't happen so add about 15%) for a total of 15 minutes a day, you will consume 315 w/hr for that usage. From this 2 way example, you can extropalate both production and consumption for your systems, have fun, I used to do this 20 times a day.
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Old 04-02-2011, 04:34   #75
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That single panal for 9 hours of production is 720 watt/hr.
Not to harp on you know, its "Wh" not watt/hr which is a rate.

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So if you have an 80 watt panal producing 17 volts, figure on 4.7 amps
Yes in theory, but unfortunately solar panels are so far from theory that in fact that statement cant be made. Look at the I/V curves, power derating with temperature, MPPT etc. This is why so many people get ouputs way below their expectations.

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