Contemplating Solar

[markwilliam1]

Thanks WME! So is your recommendation of 200 watts total would be adequate for solar and do all solar panels produce the same output? I would basically be using solar to just run fans and charge my house battery. I have a Honda 2000 generator that I can use to run my rooftop AC, or a microwave or my coffee maker if need be! Any suggestions on good panels Sir? JD recommended Renogy. This will be a next year project. Put a lot of financial love in Grannie the past few days!

[WME]

I have used Renogy and Windy Nation. Be careful with Renogy their cheapest sets are + ground, so read the fine print.

Solar panels are rated in watts and a watt is a watt. The size per watt may vary by maker.

200 w and 200 ah would be forever power. A 100w and a 100 ah would be enough south of the 45th parallel. Winter north of that would be 4-5 days before you would need to boost the batteries. Of course I don't think you would be running very many vent fans at 0 degrees

Speaking of winter, with 200 ah and no solar I could go 2 days with out charging. I'm running the rv heater and wife's CPAP. Add 100 w of solar and I could go 4-5 days. With 200 w of solar I've gone a week and still had 90% charge.

 

Edited October 8, 2016 by WME

[zero]

3 hours ago, WME said:

At full speed the Maxxair fans draw 3.7 amps@13.4 v.

200 w of solar is 16 amps at max sun, so even on a cloudy day you would have surplus power for the battery. Plus on a cloudy day you would be running the fans at a reduced power setting.

A 200 ah battery set up and 200 w of solar would run the fans for ever.

My 14" .Fantastic fan draws 6.2 amps @ 12.5 volts DC when on high-speed. I've tested it twice.  As far as solar output goes? I'm, talking about real-world figures. Not for someone living on the equator or sunniest places in the southwest.  I've taken Kyocera 120 amp panels and pointed at our brightest clearest sun here in northern Michigan and 6-7 amps @ 17 volts was the max reading in warm weather.  I've also tested Renogy 100 watt panels and the highest reading I got was 5 amps @ 17 volts.  I've also tested Sharp 200 watt panels and read 12 amps max.

Also - here is a year-long average. This in central New York with 5400 watts of solar panels with a roof mount.  365 days yielded 3600 KWHs.  That comes to 9.86 KWH per day.  A "solar" day is around 6-7 hours.  That comes to an average of 100 amps per hour @ 12.5 volts.  Note that is with 5400 watts of panels.   Now if I make the solar array only 100 watts instead of 5400 watts - that comes to an average of 1.8 amps per hour assuming a 7 hour solar day.

[zero]

47 minutes ago, WME said:

I have used Renogy and Windy Nation. Be careful with Renogy their cheapest sets are + ground, so read the fine print.

 

I've heard that but why would anyone care?  A typical solar off-grid system uses no ground for carrying power.  So it makes little difference what the polarity rating is.  Any solar panel I've seen has a positive and negative.  Same with the controllers.

[Derek up North]

7 hours ago, markwilliam1 said:

...  would it be cost effective to go 400 watts vs 200 watts?

You might want to check the physical dimension of the panels before ordering and make sure you have enough 'real estate' available on your roof. 400w sounds like a lot.

 

[markwilliam1]

This is true Derek. Won't go 400 just 200 watts. All for next year. Thanks!

[WME]

The + ground systems ground the battery + lead and the controller + . Our batteries and the lights are - grounded. They don't mix. Would you ground both ends of a 100ah 12v battery??

A house off grid who cares because its not hooked to anything external.

Besides all your fancy LED lights would not work. Plain lights no problem with reversed power flow.

Renogy even advises to get their - ground system for RVs.

[bicoastal eric]

7 hours ago, jdemaris said:

My 14" .Fantastic fan draws 6.2 amps @ 12.5 volts DC when on high-speed. I've tested it twice.  As far as solar output goes? I'm, talking about real-world figures. Not for someone living on the equator or sunniest places in the southwest.  I've taken Kyocera 120 amp panels and pointed at our brightest clearest sun here in northern Michigan and 6-7 amps @ 17 volts was the max reading in warm weather.  I've also tested Renogy 100 watt panels and the highest reading I got was 5 amps @ 17 volts.  I've also tested Sharp 200 watt panels and read 12 amps max.

Also - here is a year-long average. This in central New York with 5400 watts of solar panels with a roof mount.  365 days yielded 3600 KWHs.  That comes to 9.86 KWH per day.  A "solar" day is around 6-7 hours.  That comes to an average of 100 amps per hour @ 12.5 volts.  Note that is with 5400 watts of panels.   Now if I make the solar array only 100 watts instead of 5400 watts - that comes to an average of 1.8 amps per hour assuming a 7 hour solar day.

Everything I can find online and other forums, no one's seeing more than 2.5amps draw on high. Maybe 6.5 amps is the start up current while it comes up to speed? 

A fan should not be more than 50w.

Your other fan draws 10amps? A 1200w fan?!? You may as well run the AC

I think there's either something wrong with your fans or with your amp meter. Are you using an inline meter or a clamp on meter?

In my old rig, I could run the maxxair fan on high during the day for a week without the batteries dying. And I only had 45watts of solar. 

And led lights are a much cheaper way of saving battery power than solar is. But together, they are perfect.

[Baseball Dad]

I was just looking at this .I watched the second about the watts it takes on electric stuff.

I was looking to get a Yeti 400 the first video.Oh I forgot I was going to look at

Suaoki 100W 18V 12V Solar Panel Charger

 

Edited October 9, 2016 by Baseball Dad

[zero]

9 hours ago, bicoastal eric said:

.

Your other fan draws 10amps? A 1200w fan?!? You may as well run the AC

 

My table fan uses around 130 watts on 120  volts AC. I.e that is around 10 amps at 12 volts DC when running through an inverter. Inverters have some loss.   An RV roof-top air-conditioner, if run on DC, draws around 80-90 amps running and up to 200 amps to start.

[zero]

9 hours ago, bicoastal eric said:

Everything I can find online and other forums, no one's seeing more than 2.5amps draw on high. Maybe 6.5 amps is the start up current while it comes up to speed? 

 

No, it's a steady 6 amp draw on high. I have two of them and both read exactly the same. I cannot account for what others post on forums and don't really care. Do your own testing.  I also have a roof vent-fan from a Winnebago of late 80s vintage and that only draws around 2 amps. It also has a fan that is much smaller then the Fantastic unit and also moves a lot less air.

[zero]

10 hours ago, WME said:

The + ground systems ground the battery + lead and the controller + . Our batteries and the lights are - grounded. They don't mix. Would you ground both ends of a 100ah 12v battery??

A house off grid who cares because its not hooked to anything external.

Besides all your fancy LED lights would not work. Plain lights no problem with reversed power flow.

Renogy even advises to get their - ground system for RVs.

Automobiles have no earth-grounds that I know off.  Just positive and negative.  A negative-to-chassis system is not an earth-ground.   I am still a bit confused about the problems you are expressing.  I admit, I have not seen nor used a Renogy controller that is called "positive ground."   I have two Renogy systems and neither have any grounds.   Solar panel has an aluminum frame and a tempered glass cover over the solar-cells.  In back there are two insulated terminals.  One is negative and one is positive and neither is bonded to the metal frame. Note that in household systems - that metal frame is supposed to be connected to an earth-ground for lightning protection.  The controller also has two insulated terminals to hook  to the solar panel and two more to hook to the battery. One is negative and  one is positive and the controller body is plastic. I.e.., it is insulated.   So again - I don't understand the warning about "positive ground" here.  If by chance, Renogy sold some controllers with the positive terminal bonded to an earth-ground connection - then the smart thing to do is not to hook up the earth ground anywhere.  Like I said, cars and trucks do not have earth-grounds anyway.  The only time an RV has a true earth-ground is when it is hooked to shore-power.   You've really got me confused.  What am I missing?

[zero]

10 hours ago, WME said:

The + ground systems ground the battery + lead and the controller + . Our batteries and the lights are - grounded. They don't mix. Would you ground both ends of a 100ah 12v battery??

A house off grid who cares because its not hooked to anything external.

Besides all your fancy LED lights would not work. Plain lights no problem with reversed power flow.

Renogy even advises to get their - ground system for RVs.

OK.  In a weak moment - I looked up the tech info from Renogy.   They say in their manual . . " Please Note: This is a Positive Ground Charge Controller. If grounding is necessary, it must be completed on the positive line. If the controller is to be used on a vehicle which has battery negative on the chassis, loads connected to the controller must not have an electrical connection to the vehicle body. "

Does not look like a problem to me.  Our RVs do not have DC earth-grounds anyway so who cares?   Hook positive to positive, and negative to negative, and nothing to the chassis from the controller. Note they say "if grounding is necessary."  On an RV, it is not.  Again, what am I missing?  Also note that what Renogy is discussing is the "load" part of the controller that does not even get used for solar on an RV.   There controllers have three pairs to two terminals.  Pair #1 is POS and NEG to solar pane. Pair #2 is POS and NEG to battery.  Pair #3 is a load-controller circuit that does not get used for what we are talking about here.

[zero]

An added comment on my Fantastic Fan.  I checked it again. On high - with the windows all closed - it draws 5.5 amps @ 11.8 volts.  That is without the engine running and some voltage drop.  With a window open, on high it draws 3.2 amps.  On low - with a window open - it draws around 1.4 amps.

[markwilliam1]

Great info. Thanks!

[WME]

3 hours ago, jdemaris said:

OK.  In a weak moment - I looked up the tech info from Renogy.   They say in their manual . . " Please Note: This is a Positive Ground Charge Controller. If grounding is necessary, it must be completed on the positive line. If the controller is to be used on a vehicle which has battery negative on the chassis, loads connected to the controller must not have an electrical connection to the vehicle body. "

Does not look like a problem to me.  Our RVs do not have DC earth-grounds anyway so who cares?   Hook positive to positive, and negative to negative, and nothing to the chassis from the controller. Note they say "if grounding is necessary."  On an RV, it is not.  Again, what am I missing?  Also note that what Renogy is discussing is the "load" part of the controller that does not even get used for solar on an RV.   There controllers have three pairs to two terminals.  Pair #1 is POS and NEG to solar pane. Pair #2 is POS and NEG to battery.  Pair #3 is a load-controller circuit that does not get used for what we are talking about here.

Are you willing to risk that all the DC circuits in your rv are wired to the - on the battery and that NONE of them use a chassis ground??  Lights, water pump, vent fans, cigarette lighter??? 

Simple is easy and safe for the average Toy MH owner.

[zero]

8 minutes ago, WME said:

Are you willing to risk that all the DC circuits in your rv are wired to the - on the battery and that NONE of them use a chassis ground??  Lights, water pump, vent fans, cigarette lighter??? 

Simple is easy and safe for the average Toy MH owner.

You lost me. If I hook up a Renogy controller that is called "positive ground" for the load-circuit that goes unused - it has no effect on anything in the RV.  Regardless of what they call it, NEG goes to NEG, and POS goes to POS.  There IS no POS going to any chassis ground.

[WME]

OK go for it.

[bicoastal eric]

Jdemaris, I agree with you about the grounding issue, doesn't seem to be a problem for us, although I'm still not 100% what they're trying to say with the positive ground. as you said, the metal frame is generally not electrically connected to the solar circuit.

So assuming you have an open window (I can't imagine why you'd use an exhaust fan without a window open) your looking at less than 4 amps which is still a lot for a fan but much more reasonable.

Now, with the 120W house fan, you are right that would draw over 10amps especially with a ~15% loss from the inverter. I think you should consider a couple of those 12v clip on fans from walmart or auto zone, they pull less than 1 amp each and provide a decent breeze. 

[bicoastal eric]

ohh and the goal zero yeti.... PLEASE DON'T. I could not think of a faster way to waste money. especially for our use it doesn't make sense. and if you want portable power, get yourself a $50 jump 'n carry car jump starter with accessory plug

goal zero makes nice stuff, I have some of their smaller gadgets that are cool and handy but especially there "solar generators" are GROSSLY OVERPRICED