Solar guidance needed

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Jeremy757jones
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Solar guidance needed

Postby Jeremy757jones » Sun Apr 02, 2017 7:29 am

I'm designing a solar power system for a swamp cooler setup. I'm completely new to solar so bare with me.

Swamp cooler Setup:

12volt system

2x 35watt fans
2x 5watt pump

80 watts total

Solar setup:

1x 100watt solar panel

1x 20amp Charge controller

1x 35ah deep cycle battery

Is a 100watt panel sufficient?
Does the battery sound like a proper size? What am I missing?

Will be using in the desert sun.

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Joeln
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Re: Solar guidance needed

Postby Joeln » Sun Apr 02, 2017 9:27 am

These calculations are ideal and assume no losses.
Your losses will likely be 20% give or take so the following should be adjusted accordingly.
Running your system will take 6.7 amps, therefore your 35AH battery will be depleted in 5.2 hours if not being recharged.
I would rate the battery as under capacity for 2 reasons:
1) you might not get a charge over a given 5 hour period
2) if you run the battery down to it's full rated capacity that's not good for it, even worse is leaving it sitting for a period of time at fully discharged which does the biggest damage to a lead-acid battery.
Your panel is about right _if_ it can get full sun during the hours you use the system.
but... you probably won't be changing its orientation to face the sun throughout the day so assume some loss for that in addition to the ~20% given above. The panel will also become dusty and need periodic cleaning (assume loss - you get the idea.)

All that said, you are in the ballpark.
You might not run the swamper for as many hours a day as you get charging from the panel - that would mitigate things.
I think I'd go with more like a 90AH battery and 200W of panel, then all your losses are more than covered and you have a system you won't have to mess with.
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Jeremy757jones
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Re: Solar guidance needed

Postby Jeremy757jones » Sun Apr 02, 2017 3:13 pm

Joeln wrote:These calculations are ideal and assume no losses.
Your losses will likely be 20% give or take so the following should be adjusted accordingly.
Running your system will take 6.7 amps, therefore your 35AH battery will be depleted in 5.2 hours if not being recharged.
I would rate the battery as under capacity for 2 reasons:
1) you might not get a charge over a given 5 hour period
2) if you run the battery down to it's full rated capacity that's not good for it, even worse is leaving it sitting for a period of time at fully discharged which does the biggest damage to a lead-acid battery.
Your panel is about right _if_ it can get full sun during the hours you use the system.
but... you probably won't be changing its orientation to face the sun throughout the day so assume some loss for that in addition to the ~20% given above. The panel will also become dusty and need periodic cleaning (assume loss - you get the idea.)

All that said, you are in the ballpark.
You might not run the swamper for as many hours a day as you get charging from the panel - that would mitigate things.
I think I'd go with more like a 90AH battery and 200W of panel, then all your losses are more than covered and you have a system you won't have to mess with.



How will i fair with a 160ah deep cycle marine battery and a 100watt panel. I'm carrying all of this stuff cross country in my jeep so space is limiting me to a single panel.

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Joeln
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Re: Solar guidance needed

Postby Joeln » Sun Apr 02, 2017 3:57 pm

That's a great battery - overkill even but that's ok.

It could work if you run the swamper for fewer hours per day than you get sun. The 100W panel definitely covers your needs when it's directly facing the sun but unless you constantly re-orient the panel thats a small percentage of the time.

Then figure you show up at the playa with a full charge and leave with half charge, that's another chunk of power to make things work out...

But if you are planning on running for weeks or months you need bigger panel capacity to compensate for the fact that it will only be pointing directly at the sun for part of the time.

Two 100W panels will pack almost as easily as one...
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XPTom
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Re: Solar guidance needed

Postby XPTom » Sun Apr 02, 2017 4:36 pm

[quote] What am I missing? [quote]

Don't forget the 160 amp(Jeep JK?) alternator that is under your hood. If you dig hard and find the alternator specs they'll probably say it is rated for 95ish amps at idle(cold) and only 70ish if under hood temps are 200ish. That is still huge compared to the trickle from solar. Idling your engine for 20 min and burning a quart or two gas is more cost effective than doubling the size of your solar system or taking along a generator.

Avoid using your cigarette lighter which may only be fused to 15-20 amps. Connect to your main battery with jumper cables or other heavy wire that can handle 40-50 amps. I use a isolator to protect my main battery from discharge, but for occasional use you can connect/disconnect manually.

Don't get too greedy and hook up more battery than your alternator can handle in the hot desert.
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BBadger
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Re: Solar guidance needed

Postby BBadger » Sun Apr 02, 2017 5:26 pm

How much cooling do you need? Depending on the size of your tent or area to cool you might be able to just get away with bringing a single (or two) large deep-cycle battery and foregoing the solar panels. Solar panels are cool and all, but they're still relatively expensive. I think the 100W solar panels are like $190 a piece. Unless you're going to use them the rest of the year, they may not be worth the investment.

You should only use 50% of the battery's charge so that you don't damage the battery. The $90 12V marine batteries at Costco have about 100AH (or was it 160?), which gives you about 50AH to work with. If you're making a regular bucket cooler, FIGJAM's standard AFB1212SHE-CF00 12V fan uses 1.6A of current, while a typical 4.8W, 12V fountain pump will use roughly 0.4A of current. That's 2A of current, meaning you have about 25 hours of run-time on your single battery.

Spread out over a week, that's 3-4 hours a day, which is probably sufficient for daytime naps. If you need more, you could double up that with an additional battery, or just charge up your battery with a friend's generator or your alternator if you really need to. You could even just damage the battery by draining it further if you wanted (not suggested).

Make sure you have enough shade regardless of your bucket cooler arrangements. My tent was so well shaded that I didn't even use my bucket-cooler last year.
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Captain Goddammit
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Re: Solar guidance needed

Postby Captain Goddammit » Sun Apr 02, 2017 10:14 pm

I'm also of the opinion that buying solar just for burning man is a waste.
If you can manage to cram two of the Costco or similar 100ah batteries in your Jeep you'll probably have enough power, and just running the engine to charge off your alternator will be the most efficient thing to do if you only bring one and you need more power.
If you charge off your Jeep, it's ALL about the cables. Get 2-gauge jumpers, not those crappy 4- or 6-gauge pieces of thread.
I'd even strongly suggest using two sets of jumper cables instead of just one. Those cables are your limiting factor of how much current you get into the battery and how long it takes to do it.
This will be much cheaper, and much less pain-in-the-ass than setting up a solar system just for a swamp cooler for basically one-time use.
And hey... if your alternator fails on your road trip, you've got a spare battery to help you keep going to the nearest NAPA.
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FlyingMonkey
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Re: Solar guidance needed

Postby FlyingMonkey » Mon Apr 03, 2017 12:39 am

If this is just for a swamp cooler then why do you even need batteries? You won't need to cool much after the sun goes down. Batteries are heavy & add complexity.

I have 2 x 100W panels & 3 deep cycle batteries & an inverter for AC loads. It's a beast & weighs a ton. I built it more for fun than actual need. My panels were producing a consistent 19 volts (dusty or not) going in to the charge controller.

On thing to consider that I overlooked one year, many of the solar charge controllers need batteries hooked up to operate. Depending on your level of experience with electronics, consider using just a solar panel that exceeds your power requirement & a voltage regulator. Circuit boards are easy to make or you can just buy what you need premade.

If you need to power your margarita blender then go all out. (and invite me).

Oh yeah, be sure to test it well before you head to the Playa.
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asr9754
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Re: Solar guidance needed

Postby asr9754 » Mon Apr 03, 2017 2:51 pm

100W panel and 160 amp hour battery should be good. 35 amp hour battery is too small.
Err toward a larger battery vs larger panel.

That's the exact setup I use: 160 amphr marine battery 1 swamp cooler (per exact FJ spec), a few LEDs, I charge phones every other day perhaps, and run a few small gadgets. With a 100w panel, I barely make a dent in the battery all week. I help campmates with their chargeables too. I have run the same battery with a 35w panel and it was fine, I just didn't share as much. The big battery is the engine of this rig, not the panel. The panel just trickles power back in passively. The battery is actually driving your gear.

Wipe off the panel daily and angle it toward the sun at peak (approx noon).

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Token
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Re: Solar guidance needed

Postby Token » Mon Apr 03, 2017 5:31 pm

Sounds like two bucket coolers.

If the fan is the 12" RV fan, it has 3 settings, 1A - 3A

I'd ditch the battery and run direct from the panels.

1 x 10W panel for the pumps.
2 x 20W panels for the fans.

You may need to regulate the 20W panels if they make too high a voltage. Depends on the panel.

3 smaller panels are much easier to pack than one big one.

maladroit
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Re: Solar guidance needed

Postby maladroit » Thu Apr 06, 2017 7:51 am

I use a 90Ah battery and a 30W monocrystalline solar panel. Contrary to the good Captain, I find the solar panel well worth the investment ($60 five years ago). I set it up once and then forget about it. Sits there and keeps the battery charged. More than enough power for hexayurt lighting, a bucket cooler (since retired), a CPAP machine, air bed pump, charging USB devices, and soldering. And then hooked up to a winch on Sunday and dragging a 10,000 pound vehicle onto a trailer.

I'd rather bring the solar panel + battery than two batteries, since the solar panel is much, much lighter than another battery. And the solar panel cost less than another battery. It's completely silent and if there's sun, it's charging up...don't have to remember to do anything, don't need to open the hood and mess with jumper cables, waste gas I might need to reach Rabbit Trax, get even more dust inside the car.

30 watts isn't much but I live within those limits, and couldn't be happier with the setup. I recently added an inverter generator, but really only powers an impact driver and an air conditioner. I don't want to run a generator all night.

bhearn
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Re: Solar guidance needed

Postby bhearn » Fri Aug 18, 2017 12:26 am

Well. I guess I should have looked here before figuring out all this stuff myself, or not. Too late now, everything is ordered and on the way or already here.

I'm building a bigger swamp cooler for my yurt -- my understanding is that the bucket coolers are not up to the task. So this is a figjam-style box cooler, bigger fan (Endless Breeze), more material surface area. Power draw (fan + pump) is 1.6A on low, 3.0A on high.

So... I went with a 60W panel, a 35ah deep-cycle 12v battery, and a MPPT charge controller. I didn't want to pack in a heavier battery or a larger panel, and this seemed like it would be enough. Even with the cooler on high I should get 5 hours from a full charge without dropping the battery too low, more than I will use, I am sure. And the panel ought to restore at least that, right? No inverter, only other draw is a USB charger. Maybe some LEDs for the yurt if I have time and feel creative.

The one thing I've been trying to figure out is whether I need to ground anything. But I don't see any discussion of grounding in any BM discussion of solar.

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Token
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Re: Solar guidance needed

Postby Token » Fri Aug 18, 2017 7:56 am

Looks good.

Grounding not needed when the system is 100% running on 12V.

With a 60W panel you have plenty headroom on power generation, more that is used by the swampy so some extra for led lights and whatnot is fine at night.

I'd keep any lighting use down to 1A if running all night.

bhearn
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Re: Solar guidance needed

Postby bhearn » Fri Aug 18, 2017 8:59 am

Great, thanks!


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