Simple 100W Solar / $237 - Fiberglass RV


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Old 10-07-2019, 09:36 AM   #1
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Name: Larry H
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Simple 100W Solar / $237

Hi All,

Just noticed a simple 100W solar system that might be of use to some
people needing a small solar charging system. $237 delivered?

https://www.renogy.com/100-watt-12-v...eid=584a415a98

Take Care,

Larry H
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Old 10-07-2019, 09:53 AM   #2
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Looks like a great deal.

I don't prefer the alligator clips, but it would be easy enough to make a different attachment.
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Old 10-07-2019, 02:25 PM   #3
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Another cheap system?

Right your are, Zack...

For those of you who like to build things a bit better system could
be assembled by any decent DIYer.... The MPPT Charge Controller
is the big difference...

Parts:

100W Panel $99 : https://www.ebay.com/itm/NEW-Compact...item468581e416

Panel legs $36 : https://www.ebay.com/itm/Renogy-Sola...item41e847a11f

MPPT Charge Controller $94 : https://www.ebay.com/itm/Renogy-Rove...item85a8e71053

$229 Plus Misc assoiated parts,wire,fuses, connectors etc. Less than $300.

Larry H

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Old 10-07-2019, 05:26 PM   #4
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Bought one of these on Prime Day for a little less. Nice unit.
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Old 10-07-2019, 07:23 PM   #5
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Originally Posted by Larry C Hanson View Post
Right your are, Zack...

For those of you who like to build things a bit better system could
be assembled by any decent DIYer......

.
Maybe... I built a 100 watt solar "suitcase" using two 50 watt panels. In retrospect I should have bought the Renogy one. And the new Renogy one is even a better option.

And before that I used a single 100 watt panel with a controller inside the camper. The 100 watt panel is heavy and large (been there, done that, gave it to my brother). I have those legs also...but now they are on a shelf in my garage. A MPPT controller wont get you any real advantage over a PWM controller with 100 watts and a short wire run.

But if you are really good I'm sure you could build one at least as good as the Renogy. The question is, is it worth the effort and maybe higher expense.
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Old 10-09-2019, 05:47 PM   #6
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PWM vs MPPT?

"A MPPT controller wont get you any real advantage over a PWM controller with 100 watts and a short wire run.'

Hello Gordon,

I think you should do some more research regarding the advantages of MPPT controllers vs PWM controllers...

Larry H
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Old 10-09-2019, 06:09 PM   #7
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An MPPT controller could give 30% more output under some conditions.
I have used PWM and under most conditions the MPPT will outperform the PWM in MY experience.
I now have three 100 watt panels wired in series and it allows for more charging current under low light and poor angle conditions since the series voltage will generate an output to the battery where the PWM in series would not.
But to each his own.
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Old 10-09-2019, 06:20 PM   #8
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Originally Posted by Larry C Hanson View Post
"A MPPT controller wont get you any real advantage over a PWM controller with 100 watts and a short wire run.'

Hello Gordon,

I think you should do some more research regarding the advantages o MPPT controllers vs PWM controllers...

Larry H
Thanks.. I did.. this is part of my research, and a good read for you.

Source: Frequently Answered Questions - Bogart Engineering


C1. The debate rages: which controller is best PWM (Pulse Width Modulation) or MPPT (Maximum Power Point Tracking). Why did you choose PWM technology instead of MPPT for your SC-2030 Solar Charger?
A very good question! They BOTH have good and bad. Plenty of hype has been written already. Here’s my (Ralph’s) view:

The “good” for PWM: It is simpler and lower cost technology. Under some common circumstances–it can actually deliver more amps to the battery. That could be when:

(1)days are moderate or warm, with few clouds.

(2) batteries are charging at over 13 volts, (in a 12 battery system) which they almost always are when actually CHARGING.

(3) Panel voltage is properly matched to the battery voltage, for example “12V” panels are being used with a 12V system.

PWM is actually more “power efficient” than MPPT–which means less total power loss in the controller itself. So heat sinks in the design can be smaller (and less expensive). Missing in most analysis of MPPT is that there is always a conversion loss with MPPT, which tends to be higher the greater the voltage difference between battery and panels. That’s why PWM can actually beat MPPT under circumstances described above.

Some places that analyze MPPT assume that panels with 30V open circuit voltage are being used in a 12V system. Any good MPPT system will easily provide better performance in that case. They also may assume batteries are charging at 12 or even 11 volts, which is unrealistic. Lead acid batteries are typically below 13 volts only when discharging, or perhaps charging with very little charging current–meaning the actual potential gain in amps is not great.

The benefit for MPPT becomes apparent if you use panels not voltage matched for the battery. If they are not, MPPT will utilize more of the potential energy of the panels. For example, if you use 24 volt panels to charge a 12 volt battery system you must use MPPT, otherwise you would be using your panels very inefficiently. If you are trying to use PWM in that case, you are misusing the PWM technology.

Another potential benefit with MPPT is that if distance between panels and batteries is far, smaller wire can be utilized by running panels at higher voltage to the batteries. Running at twice the voltage reduces wire size to 1/4, which for a long run can be a significant saving in copper wire.

If temperatures are low enough, the slightly less power efficiency of MPPT will be compensated by the higher panel voltages, which will result in a little more battery current. But in actual measurements we made using a commonly sold MPPT solar controller, this would occur at temperatures less than 55 F degrees (in full sun, when charging at more than 13 volts), where there is a slight advantage to MPPT in my location (Boulder Creek, near the California coast). As temperature drops below that (in full sun) MPPT will get some advantage, such as could occur at high elevations in Colorado in the winter. Potentially this would be maximum about a 2.5% improvement in amps output for every 10 degrees F lower in temperature (or 4.6% per 10 degrees C colder. I’m using data from Kyocera KD-140 panels.)

There can be theoretically optimal situations (that I don’t personally experience where I live) where MPPT could give some advantage: that is when solar current is present, but the batteries are quite low in charge–but because loads are high and even greater than the solar current the batteries are still discharging despite the solar current. Under these conditions the voltage COULD be at 12.5 volts, or even lower. Again, using data from Kyocera panels, (“Normal Operating Conditions”) there is a theoretical maximum gain over PWM of 20% current assuming NO MPPT conversion loss and no voltage drop in the wires to the panels, at 20C (68F). With PWM, the voltage drop in the wires in this case would not affect the charging current. Now if in addition you lower the temperature to below freezing at 28 degrees F (while sun is shining) you might actually get up to a THEORETICAL nearly 30% gain while the batteries are discharging.

The only REALLY BAD part of MPPT, is all the hype surrounding it–for example one manufacturer advertises “UP TO 30% OR MORE” power harvested from you panels. If you are using solar panels properly matched to the batteries, 30% ain’t gonna happen unless it’s EXTREMELY cold. And your batteries have to be abnormally low in charging voltage–which tends not to happen when it’s cold (unless you assume the battery is still discharging while solar is happening). Virtually all the analyses I’ve seen touting MPPT on the Internet ignore the conversion loss, assume really cold temperatures, assume unreasonably low charging voltages, assume no voltage drop in the wires from panels to batteries, use STC conditions for the panels (that the marketing types prefer) rather than more realistic NOCT conditions, and in some cases assume panels not voltage matched to the batteries.

The other thing that is misleading about MPPT, is that some manufacturers make meters that show both the solar current and the battery current. In almost all cases for a well designed MPPT type the battery current will be greater. The engineers making these know better, but it is implied (by marketing types?) that if you were NOT using MPPT you would be charging your batteries with only the SOLAR current that you read on their meters. That’s not true, because the PWM BATTERY current should always be higher than the MPPT SOLAR current. It is the nature of the MPPT that maximum power occurs when the current is lower than the maximum, so they must operate there to get the maximum power. So to properly compare the two you need to compare MPPT with an actual PWM controller in the same circumstances.

Finally, the reason we went to PWM is that I was anticipating that panel prices were going to drop (which they certainly have over the last 5-10 years!) and that the small advantage of MPPT (under conditions where the correct panels are used for the batteries) would not justify their additional cost and complexity. So my thinking, for more total benefit per $, put your money in an extra panel rather than a more expensive and complex technology.
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Old 10-09-2019, 06:42 PM   #9
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MPPT VS PWM depends o what the adviser is invested in.
Certainly PWM COULD be more efficient, but at up to 98% for the EPEVER 40 amp it is hard to be much better.
In my case since the panels are mounted "flat" on the roof every advantage I can get is worth it.
I have three 100 watt panels to provide power for my Amateur Radio Emergency Service setup and since in Florida the most likely cause for the need to respond is a hurricane that took down most trees so shade might not be a problem.
I have wired the EPEVER 40 amp system into the power inverter distribution system so that the controller can determine the load as well as control the solar panels.
This setup is by far the best I have had, having tried several PWM controllers.
This setup begins producing a charge output earlier and last later and produces higher charge or power output for the 12 volt systems than any other I have tried.
I have an inverter generator back up (dual fuel LP or gasoline) but in an actual emergency fuel can be in short supply so solar in critical and the most you can get out of your panels is a good thing.
If you have smaller electrical needs a simpler system will work. but when you need all you can get then go with MPPT and series panels.
I usually have the string of panels working in the 60 volt range with reasonable sun exposure, but the panels produce charging current with any voltage higher than the actual battery voltage at the time.
Of course this is NOT a simple 100 watt single panel system.
You can get a simple system with a $100 panel and a $20 PWM controller along with a little homebrew brackets and wiring
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Old 10-09-2019, 07:54 PM   #10
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Originally Posted by redbarron55 View Post
...
Of course this is NOT a simple 100 watt single panel system....
And that is exactly my point.. MPPT is usually the best choice for higher voltage, multi-panel systems like those found on the roofs of homes or in commercial applications, but for most small campers using maybe 100 to 300 watts and 12 volt storage voltage (i.e. one or two RV batteries), there is no real advantage in spending more money for a MPPT controller.
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