How much solar do I need?

[Canine]

I know Blue Sky Energy intimately, so that is what I can answer to; however, go ahead and start your own thread instead of tacking on to this one. We'll get you set up.

 

[Gr8ful]

I just bought a great ambulance with 165 amp alt & 2 new 12v starting batts alt, I also have 4 new 6v deep cycle batts & found new panels for 50 cents a watt local so was going with 4 275 watt panels, charge controller & a battery isolator. I have 2 1000 watt & 1 2000 watt inverters & a couple 200 watt & everything else needed.

 

[Canine]

I just bought a great ambulance with 165 amp alt & 2 new 12v starting batts alt, I also have 4 new 6v deep cycle batts & found new panels for 50 cents a watt local so was going with 4 275 watt panels, charge controller & a  battery isolator. I have 2 1000 watt & 1 2000 watt inverters & a couple 200 watt & everything else needed.

Holy cow! I have a ton of solar and even I'm jealous. Nice set up!

 

[vanlifeadventures21]

Those are good recommendations. We have 200W and I feel like it’s plenty for the average dweller like you suggest.

I do still think it’s important for people to know what they are powering before buying a large system though.

It doesn’t make much sense to buy 600W if you can get by with 200W.

Simple switches like using a Jetboil instead of a coffee pot could save you hundreds of dollars but if you have no idea how many watts the coffee pot uses you might think you NEED 400+ Watts when you don’t.

A larger system can also be more complex to build leaving more room for stuff to go wrong.

 

[John61CT]

No, it's just money.

When heading into cloudy places, or winter in high latitudes, you **need** 5x bigger a system than in summer, or Arizona.

 

[Seminole Wind]

No, it's just money.

When heading into cloudy places, or winter in high latitudes, you **need** 5x bigger a system than in summer, or Arizona.

deffinately a challenge in the pacific north wet in the winter. yet, 5 times may be an understatement at times. i am in coastal southen oregon predominately. for 2 years i ran with 470 watts flat mounted solar and powered a 2.5 cubic foot chest freezer, recharged a 700 watt hour electric bike, an excessive number of hours on my laptop and the other incidentals. most days i would hit absorb by noon and float long before the sun got low on the horizon. i would see around 1.5kwh (kilowatt hours) from the solar each day. and since i was in absorb/float a large portion of the day the panels had the capacity to make more under those conditions IN THE SUMMER. but in the winter i had to runn the generator once or twice a week and had to cut back on cycling(not hard due to rain and cold) and laptop time. this fall i just upgraded my solar from 470 watts to 1770 watts on the bus. even with all those panels i am still not keeping up. i have had to cut back on laptop time and bike charging. three days ago i only got 180 watt hours from my 1770 watt array. and the peak output that day was 105 watts. as i am testing this new system still i isolated my bike and laptop charging to the generator and only used the solar to try and keep up with the freezer. 5 days ago i fully charged and then equalized the house bank. since then i have hit absorb only on 2 days and have not got back to full. fortunately if i can get through a week or 2 of low light from clouds and rain. when the sun does come out i have a good chance of fully recharging the house bank.

cloudy rainy weather in a northish latitude really put a crimp is solar production

 

[gchristi1]

After going through this thread, I really like the mental challenge of doing the math in my head. You have to keep switching between decades, factors of 12 and derating by a factor of 50%.

10 amp-hours is 120 watts, that means you need 240 watts, and being me, I round up to 300 watts. Multiply the 10 amp-hours by number of usage hours and so on.

 

[Dhalamar]

Alright, maybe someone can help me here because this stuff is starting to hurt my brain a bit... I've never been much of a math guy.

I'm full timing in a camper right now, plugged into a house via an extension cord.

I'm experimenting about with the minimum I'd actually need...

Right now with my gaming laptop plugged in and working hard (along with a 10" fan, 8" fan and an LED lamp going all full blast... and a weather radio) I'm using about 175W. With my Chromebook plugged in and charging I'm using about 80W, and no computers I'm at about 50W.

In my eventual van build I'm going to have 220W of solar and a 105ah battery (that's in the camper right now) with a 400W Everstart inverter that I've got laying around (I'm going to get better as I have the money). I've also got a 13W briefcase style panel setup and a little 21W foldable solar panel thing (imagine the kind that backpackers have strapped to their backpacks)

I'm also counting the fact that in an eventual van build I can also use a little 12V inverter to power things while I make pilgrimages to the Chicago area that's about a 10 hour round trip from me. I've got a 88.8Wh battery bank with an 80W AC port on it, an Anker Powercore 10050 battery. I sling doughnuts out of a commercial minivan for work so I'm sure I could leech power off that at work. lol

I'm also considering the fact that I won't need to have this stuff running all the time of course. Laptop doesn't do me a hell of a lot of good while I'm driving. heh

But how would I figure out how long I could run what I'm wanting at that maximum 175W scenario off the battery I've got counting the solar? I'm just wondering if the panels would be (weather permitting of course) potentially be enough to keep up with or outrun the drain on the battery?

 

[tx2sturgis]

How many hours a day will that gaming machine be running while you are on solar?

175 watts of power drain for a few hours during mid-day (daylight) no problem, but 175 watts for 10-15 hours a day, nope.

220 watts of solar is probably enough to keep the batteries happy if you can reduce the loads by at least 50%, especially at night.

 

[Dhalamar]

How many hours a day will that gaming machine be running while you are on solar?

175 watts of power drain for a few hours during mid-day (daylight) no problem, but 175 watts for 10-15 hours a day, nope.

220 watts of solar is probably enough to keep the batteries happy if you can reduce the loads by at least 50%, especially at night.

Most of what the solar would be used for in an off grid environment to be able to game for a little bit, run fans that currently total about 40W (though that's going to drop significantly in the near future) and recharge batteries that consist of that Anker PowerCore 10050 or that Hypergear 88.8Wh/24,000mAh. Not sure how much power they pull when charging off hand.

Everything but the gaming laptop can potentially be recharged or ran using either of those two battery banks... and of course anything USB can also run off any laptop or (with an adapter) phone battery... and my phone has a 5,000mAh battery in it.

For regular internet use, I've got a Chromebook that has a battery life of around 7 hours.

As far as at night? Unfortunately, that's when I tend to game the most is evening/night... usually an hour or two. So about 100W for it by itself for 2 hours or so. 4 at the top end. I usually try to get to sleep around 8 or 9PM to leave for work at around 2:30AM where everything would just be shut off.

So in an off grid scenario I could live without falling asleep to YouTube videos and just go with a 10W fan that optionally runs off of D cells, and can run for HOURS off that Hypergear battery.

Also starting to investigate compressor fridges, but that's a little further off in the future because they're damned expensive. lol

Eventually I want to get a better battery setup, like maybe sometime getting one of those "solar generators". Use the solar setup to recharge and/or offset it. I've KINDA got that with that Hypergear battery bank, but obviously 80W with 88.8Wh is extremely limited. Got it on sale for 30 bucks a while back.

I'm also looking at replacing my 8" 30W fan with a 9" USB OPolar that's advertised at 4W.

I'm still in the investigation stages since I don't even have the van yet. I'm just trying to figure out my power usage versus what I'm gonna have for solar in a van or off grid power outage kinda situation.

 

[allykayte]

Help!! My husband thinks we can run an air conditioner, my cpap, a tv and our phones and computers off of 2 of harbor freight's 100 watt kits. We have a Jayco 1406 popup camper and plan to summer in Wisconsin and Colorado area then winter in Arizona. I just can't get through to him. He's a stubborn cus.

 

[MrAlvinDude]

Help!! My husband thinks we can run an air conditioner, my cpap, a tv and our phones and computers off of 2 of harbor freight's 100 watt kits.

Demand that he proves to you how he is going to manage that (magic) feat!

Demand that part of his proof includes a simple Watt calculation.


He will likely swear a lot trying to create the proof. And in frustration he might give up, trying to create the proof. But hopefully he will at least have learned that: Volt x Amp = Watt.  
OR
he will gain the knowledge and insights needed to make things run on solar. So you will at least be able to run the Cpap machine all night long!

Either way, it will be a beneficial exercise for him.

 

[MrAlvinDude]

allykayte, do you know how to do the watt calculation on the solar setup? And the watt calculation on a battery? And the watt calculation on each of your devices?

 

[B and C]

How many watts does the A/C pull as compared to 200 watts of solar? This should be a first big clue.

 

[MrAlvinDude]

How many watts does the A/C pull as compared to 200 watts of solar? This should be a first big clue.

Exactly!

A super efficient (and small 5000 BTU) A/C will typically use 400 to 500 watt of energy when running.

So to run such a small (and super energy efficient) A/C for ONE hour, it will take 2-3 hours of IDEAL SUN conditions on those 2 x 100W panels.

Or in other words, it can run for about 20 minutes every hour of perfect sun.

So the A/C alone is basically a no-go for 2x100W panels.


But all the other things ( my cpap, a tv, phones and computers) might be able to be powered, to some extent at least, on just 200W of solar.

But let us do some example calculations.

 

[B and C]

The other items listed is doable on 200 watts. I have 200 watts on the roof and another 200 watts portable. I also have a 350 Ah AGM battery bank. I can't run A/C on solar. Sometimes I have to use the portables to help recharge like after rain days or really cloudy weather or when I park in the shade. It is easier to conserve power than it is to produce it.

 

[MrAlvinDude]

The solar panels.

Under ideal sun conditions the 2 x 100W panels can (at best) produce 200W every hour (h), so 200 Wh for, let us say 8 hours, is 8 x 200 = 1600Wh produced in one (perfect sun) day.

So the devices should never use more than this amount of energy in an ideal 24 hour period.


So if a device uses 20W it can be run 1600 / 20 = 80 hours ( where '=' means 'equal to' )

Or if it uses 36W it can be used for 1600 / 36 =~ 44 hours ( where '=~' means 'close to' rather than 'equal to' )

 

[highdesertranger]

a Harbor Freight panel is NEVER going to produce it's rated output. highdesertranger

 

[jimindenver]

Help!! My husband thinks we can run an air conditioner, my cpap, a tv and our phones and computers off of 2 of harbor freight's 100 watt kits. We have a Jayco 1406 popup camper and plan to summer in Wisconsin and Colorado area then winter in Arizona. I just can't get through to him. He's a stubborn cus.

Life is often cruel to the stubbornly ignorant. I often hear "but I have solar" when the direct relationship between how much solar and how much you want to do just doesn't click. Sadly by the time it starts to click they are not spending their money on more solar, instead it's spent on replacing the batteries damaged by trying to do too much with too little solar.

It takes 700-800 watts of solar to produce enough power to run a efficient window A/C without draining the batteries at the same time. A portable system can run it earlier and later than a flat mounted system simply because the panels are kept at peak by facing the sun longer.

Two 100 watt HF kits are 8 panels to store, set up and move around. 800 watts worth of HF kit is 32 panels and that is still only enough to run the A/C when the sun shines. He would need twice as much to run the A/C at night and recharge the batteries while running the A/C the next day. I hope that your pop up is a toy hauler because you will need a lot of space and he will spend all his time setting up and moving the panels all day.

There are better ways of doing it.

 

[Elbear1]

Hell we could power the planet with 100kw if 2 HF kits runs an AC. LOL