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Old 01-12-2016, 04:34 PM   #21
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See above, am I missing something? Won't you get all the power through PWM until you are charged?
Here's a 12V 100W panel: 100 Watt 12 Volt Monocrystalline Solar Panel | Renogy Solar

Its 12V nominal, but actual specs are around 18.9V @ 5.3A. With PWM, that 5.3A would be maintained on the output side of the controller, but dialed down to only 12-14V as needed based on the charge state of the battery. Best case at 14.5V * 5.3A = 77W. That's the loss that Don was describing, I believe.
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Old 01-12-2016, 06:22 PM   #22
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Yes you are right. I shouldn't post before coffee I guess. I still agree with Handy Bob that for small systems you get more bang for the buck buying an additional panel over paying for the MPPT. But that assumes you have room for the panel, etc. The most important part is to go into such an installation being educated and using quality components.

And then being on the road with solar is such a nice way to go. Yes the Honda generators are "quiet" but i have camped across the road from them and they get tiresome when they run all day.
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Old 01-12-2016, 06:28 PM   #23
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Here's a 12V 100W panel: 100 Watt 12 Volt Monocrystalline Solar Panel | Renogy Solar

Its 12V nominal, but actual specs are around 18.9V @ 5.3A. With PWM, that 5.3A would be maintained on the output side of the controller, but dialed down to only 12-14V as needed based on the charge state of the battery. Best case at 14.5V * 5.3A = 77W. That's the loss that Don was describing, I believe.
That helps. Didn't realize that the 12 volt panels went that high. Looked at the specs, but don't understand all the different numbers and what they are for.

What is the difference between Poly and Mono panels? Anything worth worrying about?
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Old 01-12-2016, 06:31 PM   #24
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And then being on the road with solar is such a nice way to go. Yes the Honda generators are "quiet" but i have camped across the road from them and they get tiresome when they run all day.
That's what I'm thinking! Would still run a genny for air conditioning (wouldn't be around others for this) or microwave which would only be short stints.

Who knows, maybe I'll end up being able to run the microwave (bigger inverter) and leave the genny at home!
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Old 01-12-2016, 07:00 PM   #25
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Which Solar Panel Type is Best?

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Originally Posted by Cdash View Post

What is the difference between Poly and Mono panels? Anything worth worrying about?
Everything you wanted to know about the different panels!

Which Solar Panel Type is Best?

Don
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Old 01-12-2016, 07:27 PM   #26
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Everything you wanted to know about the different panels!

Which Solar Panel Type is Best?

Don
Thank you, extremely helpful!
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Old 01-12-2016, 10:23 PM   #27
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Here's a 12V 100W panel: 100 Watt 12 Volt Monocrystalline Solar Panel | Renogy Solar

Its 12V nominal, but actual specs are around 18.9V @ 5.3A. With PWM, that 5.3A would be maintained on the output side of the controller, but dialed down to only 12-14V as needed based on the charge state of the battery. Best case at 14.5V * 5.3A = 77W. That's the loss that Don was describing, I believe.
Ignorance here so...
Why does this matter? Aren't we just wanting to put Amps back into the battery? If the Amps don't change, only wattage, what are we PWM users loosing?
Thanks in advance,
Jeremy
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Old 01-13-2016, 07:17 AM   #28
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There is a good channel on YouTube that answers a lot of the questions asked here.

https://www.youtube.com/user/AltEStore

Once you have the knowledge and match the system to your battery capacity, you should get many years of low maintenance performance out of your system.
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Old 01-13-2016, 08:18 AM   #29
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Ignorance here so...
Why does this matter? Aren't we just wanting to put Amps back into the battery? If the Amps don't change, only wattage, what are we PWM users loosing?
Thanks in advance,
Jeremy


Pulse Width Modulation works by turning the power applied off and on. During the off cycle, no power is received by the battery. As the battery approaches about 90% charge, the controller spends more and more time in the off part of the cycle. What you get is high amperage pulses followed by rest as the battery voltage returns to the controller voltage setpoint. One of the side effects to this is increased water loss due to gassing in the battery.

MPPT feeds a steady amperage to the battery. This amperage decreases as the battery approaches full charge. The output is a steady trickle charge, charging the battery to full saturation quite efficiently. Charging this way has very little water loss as gassing is kept to a minimum.

The other advantage is performance in low light conditions. Because PWM uses lower voltage panels, higher solar flux rates are needed to bring the panel voltage above battery voltage so charging can begin. Because MPPT can accept much higher input voltages, you can take advantage of higher voltage panels. Example, half output on a 18 volt panel = 9V, no charging, half output on a 36 volt panel = 18V, battery charges.

My personal experience using a 24 volt (36V open circuit) panel show that the system starts charging as soon as it gets light out, even before sunrise, and even on cloudy days still charges at a reduced rate.
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Old 01-13-2016, 08:29 AM   #30
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By the end of the day everything needs to be set based on your usage.
Do you use toasters? Do you fry eggs on electric appliances? Does your wife dry her hair with a blower?
If you intend to run a fridge/freezer, I doubt you can make it with less than 400W...

I have a boat with a 10w solar panel, morningstar charging controller and AGM Battery. My set up work for me because we only use the boat during weekends, all my lights are LED's and we only use the inverter eventually for light uses like a small blender, a small vaccum cleaner and the charging of the I-stuff. So the 10W can keep the battery 100% most of the time. The battery goes to 50% by the end of a two day stay.
I'm also following liveaboards for years now and it seems that the cheapest route is Trojan Golf Cart Batteires linked to at least 200W of solar and one small charge controller for each solar panel (that seems to be the more trouble free set up).

Trojans are heavy but reliable if you take care of the water level in them.
Again, the amount of Solar will depend of your usage.
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