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countrygirl
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# Posted: 27 Oct 2014 10:37am
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We got 6 new solar panels this year to add to our grid. They were just on the ground most of the summer on small stands, while we tried to decide where we should put them. Then it came to me, we need a bigger wood shed, and the panels make a big roof. We will start splitting wood in the next 2 weeks, so know was the time to build. Knowing that we will and 6 more panels next year we have dug the posts in for the next phase. Only problem buying panels at different times, they very in size slightly.
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Borrego
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# Posted: 27 Oct 2014 03:29pm
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Great idea!
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MtnDon
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# Posted: 27 Oct 2014 03:37pm
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Cool! When buying panels at different times the other thing that needs watching is the Imp and the Vmp ratings, IF they are to be connected to the same charge controller.
Connected in series the Imp should be matched as close as possible, within 10% is a general rule. What happens is the lowest Imp of the series string is going to govern the maximum output of the set in series. OTOH when connecting in parallel it is the Vmp that should be matched as close as possible. Again, the general rule is within 10% with the voltage output of the ones in paralllel being governed by the panel with the lowest Vmp. Just info for all in case you already were up on that.
Of course using a second or third charge controller with the new and different PV panels is also a solution. However there are other pitfalls when using multiple CC's.
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countrygirl
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# Posted: 28 Oct 2014 10:25am
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Quoting: MtnDon Cool! When buying panels at different times the other thing that needs watching is the Imp and the Vmp ratings, IF they are to be connected to the same charge controller.
they are all the same Imp and Vmp connected in MidNite Solar Combiner.
This is what we have right now
Deep Cycle Batteries 8
Solar Panels250PE Watt SP 9
Inverters Magnum AE 4000 watt 24 VDC 120/240 both Inverter with 105 amp charger
Charge Controllers
Windmill 600W Wind Turbine Coleman
next year hopefully 6 more panels 2 more batteries.
We want the panels to be low for cleaning, but not an eye sore.
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creeky
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# Posted: 28 Oct 2014 03:53pm
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nice system.
can I nitpick? you probably know this but:
you only need one charger. 105 amps at 24 volts. dat's a lot of charging power when you need the genny.
also: buying batteries in batches means you throw away x years of life. basically with lead acid your battery pack is as old as the weakest battery. can I ask how much amp storage you have? do you need more storage*?
multiple charge controllers are no problem. yes one controller will occasionally make the second redundant if they are not mated ... but (I have two controllers) big deal. they charge fine and work well together. sure, we could dot the i and cross the t. but it's a great solution to get more power into your system at times of low solar production.
imho. the best way to grow a system is start with "over paneling" (say 8 panels on one controller) and then multiple controllers (6 on each in your 250w/24 v system) ... and finally expand your battery pack with an all new pack.
for this reason
* by storage I mean what are your loads. for the most part you only need power storage over night and early morning. after that you can draw straight from the panels, no?
so, with the addition of 6 more panels and another controller (similar to my system) I've found rather then add more batteries I've simply changed when I use power. I use my dishwasher, do laundry, run the microwave for longer periods of time, stream internet movies/music after the sun has given my batteries a boost (the afternoon basically) ...
and I am saving money for a new lithium ferrous phosphate battery system rather than continue to pour money into toxic lead ...
throwing that out there... hope it helps.
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