Betteries, Batteries, Batteries Oh My!

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Betteries, Batteries, Batteries Oh My!

Post by MFOB » Wed Mar 25, 2015 10:25 am

I read and read this forum about Solar and Batteries and Loads needed and so on and so forth. But I have yet to come to the conclusion of what size Solar Panel I need.

I have a 110aH Deep Cycle Battery. Last year I had it running a Figgy Cooler, and an inverter with phone/camera charger. I had a tiny panel maybe 4" by 16" with probably 18 or 20 ga wires. I felt it to be quite small and more of a trickle charger, but "most" of the stuff worked, albeit slowly chargers charged, coolers cooled, etc. But I didn't have a tester and who knows if I just didn't use much power after all and the Solar Panel did nothing. All I know is Th, F, S, Su, M, Tu it worked pretty good, then later in the week up to the burn it got worse, meaning the fan turned slower, chargers charged slower etc. I have a feeling the Solar Panel didn't charge much, I wasn't using much energy, so I was probably just using battery all week.

All the above is blah blah blah, I want to charge a 110aH battery during the 4 peak hours of the day.

10W panel, 20W panel, 50W?

Thanks
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Re: Betteries, Batteries, Batteries Oh My!

Post by Captain Goddammit » Wed Mar 25, 2015 10:39 am

If you expect to charge only 4 hours a day you better get the biggest panel you can.
This is a case where bigger is better anyway. Solar panels usually make less than their ideal-conditions maximum.
You could also just bring two batreries. Or a little extra gas and some jumper cables and charge off your vehicle a few hours later in the week.
Solar isn't really cost effective for a once a year trip.
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Re: Betteries, Batteries, Batteries Oh My!

Post by Elderberry » Wed Mar 25, 2015 10:47 am

What about using a solar panel calculator? This electrical stuff can really be confusing, at least for me. But one of the first things that came up when I Googled it was: http://www.batterystuff.com/kb/tools/so ... orial.html Which also links to a calculator.

If you can understand it, it might help??
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Re: Betteries, Batteries, Batteries Oh My!

Post by Bemerritt » Wed Mar 25, 2015 11:03 am

I am planning on using a similar setup with a 100 watt panel. Can be found online for about $150. This should allow me to run a cooler, lights and charge batteries all week. Also using a ~100 ah battery.

Let's say half of those amp hours are usable. So you have 50 amp hours available each day. 50 amps x 12 volts = 600 watts. From research and anecdotal evidence found online, 5-6 hours of peak performance from your solar panel is considered to be the ceiling, but attainable. So on a perfect day, you should be able to replenish your battery from the previous days usage. Obviously a slightly larger panel wouldn't hurt, but the price point of the 100ah battery and 100watt panel worked within my budget.

Hope this helps!

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Re: Betteries, Batteries, Batteries Oh My!

Post by Just_Joe » Wed Mar 25, 2015 11:04 am

I wouldn't waste any money on less than a 50 Watt panel. It will "fill" your battery to the tune of about 3 amps per hour of sun. You need to keep it pointed at the sun, and use as short/thick wires as possible.
It's not to hard to put a cheap meter inline with your stuff while it's running and see how many amps per hour it's using.
You don't want you battery to fall below ~1/2 its rated capacity (55 amps), which is ~12 volts (after resting with no load for an hour or so).

I've never done it but the Captain's jumper cable suggestion would send a lot more amps to the battery in a much shorter time, and cost a helluvalot less $.

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Re: Betteries, Batteries, Batteries Oh My!

Post by mooserider » Wed Mar 25, 2015 11:32 am

Here's another way to calculate it. First, figure out all the power you need, then figure out where you're going to get it from.

Daytime and nighttime loads are a little different. The battery alone has to have enough capacity to be able to carry the nighttime load (since there is no sunlight to energize the solar panels), but the solar panel has to put out enough power for both the daytime and nighttime loads (running the daytime load and simultaneously recharging the battery for the next nighttime load).

Let's take an example. Let's say (just for discussion's sake), your swamp cooler pump and fan draw 2 amperes all day at 12 volts, your nighttime safety lighting draws 3 amperes, and your "active" nighttime lighting draws an additional 3 amperes (but is only used from 6pm to 2am when you go to bed), and we have a twelve hour day (6am to 6pm). The ampere-hour formula tells you how much charge you need to run that stuff. So the nighttime safety load is 36 amp-hours (3 amps x 12 hours), the nightime active load is 24 amp-hours (3 amps x 8 hours), and the daytime swamp cooler load is 24 amp-hours (2 amps x 12 hours).

Therefore, you need 60 amp-hours of battery capacity. Since a battery should not be discharged below 50% (or it will be damaged and won't hold a charge), you really need a minimum of 120 amp-hours of battery capacity.

To recharge the battery the next day and run the swamp cooler, you need at least 84 amp-hours from solar power (replacing 60Ah in the battery, plus 24Ah to the swamp cooler). You only get about 10 good hours of sunshine (near dawn and dusk you get very little power), so to get 84 amp-hours, you'll need panels that can deliver at least 84 amp-hours / 10 hours = 8.4 amperes most of the day. Since solar panels are not 100% efficient (due to dust, non-perfect-aiming, clouds, losses in the charge controller, etc.), we will estimate the necessary wattage by calculating the desired current at the panel operating voltage of 18 volts (higher than battery voltage of 12.8 volts). So 8.4 amps x 18 volts = 151.2 watts minimum solar panel capacity.

Notice that:

(a) these are only assumed load numbers; check the actual current draw of each of your devices for the actual numbers to plug in.

(b) this is the bare minimum capacity. If you have a dust or rain storm, you will need more battery capacity to tide you over until sunshine is available, and more solar power to play catch-up on recharging the batteries when you finally get some sunshine. It also doesn't account for the fact that battery charging is not 100% efficient, so you'll need more than your nighttime load of incoming solar charge to do the recharging.

Feel free to plug in your own numbers and see what you get.

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Re: Betteries, Batteries, Batteries Oh My!

Post by MFOB » Wed Mar 25, 2015 11:39 am

apavlin wrote:Here's another way to calculate it. First, figure out all the power you need, then figure out where you're going to get it from.

Daytime and nighttime loads are a little different. The battery alone has to have enough capacity to be able to carry the nighttime load (since there is no sunlight to energize the solar panels), but the solar panel has to put out enough power for both the daytime and nighttime loads (running the daytime load and simultaneously recharging the battery for the next nighttime load).

Let's take an example. Let's say (just for discussion's sake), your swamp cooler pump and fan draw 2 amperes all day at 12 volts, your nighttime safety lighting draws 3 amperes, and your "active" nighttime lighting draws an additional 3 amperes (but is only used from 6pm to 2am when you go to bed), and we have a twelve hour day (6am to 6pm). The ampere-hour formula tells you how much charge you need to run that stuff. So the nighttime safety load is 36 amp-hours (3 amps x 12 hours), the nightime active load is 24 amp-hours (3 amps x 8 hours), and the daytime swamp cooler load is 24 amp-hours (2 amps x 12 hours).

Therefore, you need 60 amp-hours of battery capacity. Since a battery should not be discharged below 50% (or it will be damaged and won't hold a charge), you really need a minimum of 120 amp-hours of battery capacity.

To recharge the battery the next day and run the swamp cooler, you need at least 84 amp-hours from solar power (replacing 60Ah in the battery, plus 24Ah to the swamp cooler). You only get about 10 good hours of sunshine (near dawn and dusk you get very little power), so to get 84 amp-hours, you'll need panels that can deliver at least 84 amp-hours / 10 hours = 8.4 amperes most of the day. Since solar panels are not 100% efficient (due to dust, non-perfect-aiming, clouds, losses in the charge controller, etc.), we will estimate the necessary wattage by calculating the desired current at the panel operating voltage of 18 volts (higher than battery voltage of 12.8 volts). So 8.4 amps x 18 volts = 151.2 watts minimum solar panel capacity.

Notice that:

(a) these are only assumed load numbers; check the actual current draw of each of your devices for the actual numbers to plug in.

(b) this is the bare minimum capacity. If you have a dust or rain storm, you will need more battery capacity to tide you over until sunshine is available, and more solar power to play catch-up on recharging the batteries when you finally get some sunshine. It also doesn't account for the fact that battery charging is not 100% efficient, so you'll need more than your nighttime load of incoming solar charge to do the recharging.

Feel free to plug in your own numbers and see what you get.

Thanks, Exactly the answer I was looking for.

I also tried the calculators, no deals. I'm a Civil guy, not an Elec guy, I tried and it looks like a diff language.
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Re: Betteries, Batteries, Batteries Oh My!

Post by MFOB » Wed Mar 25, 2015 11:41 am

Captain Goddammit wrote:If you expect to charge only 4 hours a day you better get the biggest panel you can.
5-6 good hours of Direct sun with a decrease or "safety factor" is how I got to 4. I know its sunny for much longer, but direct is what I was going for.
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Re: Betteries, Batteries, Batteries Oh My!

Post by MFOB » Wed Mar 25, 2015 12:08 pm

Just_Joe wrote:I've never done it but the Captain's jumper cable suggestion would send a lot more amps to the battery in a much shorter time, and cost a helluvalot less $.
Sounds reasonable.

How many amps would a jumper cable deliver from the car?
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Re: Betteries, Batteries, Batteries Oh My!

Post by mooserider » Wed Mar 25, 2015 12:25 pm

MFOB wrote:
Just_Joe wrote:I've never done it but the Captain's jumper cable suggestion would send a lot more amps to the battery in a much shorter time, and cost a helluvalot less $.
Sounds reasonable.

How many amps would a jumper cable deliver from the car?
Note that the Captain's advice about jump-charging your battery bank from your vehicle is perfectly valid. But it requires opening your vehicle (more dust!) and uses up more of your fuel (a car is an inefficient battery charger, because the battery charging alternator is a secondary load on the engine after the primary load of propelling the vehicle, therefore the car is not optimized for fuel efficiency when just charging). So, you could avoid the extra solar capacity for non-sunny days and use the vehicle to make up the charging shortfalls. Just don't let the batteries get flat-lined, or they won't hold a charge from any source (vehicle or solar).

Also, look at the charging time. A car alternator is sized to carry the normal electric load of the car (ignition, radio, lights, windshield wipers, A/C, etc.) plus a small surplus to recharge the car battery for the high-current but very-short-time load of starting the engine (only a few seconds, not hours, of cranking the starter). Therefore, unless your vehicle has a non-standard over-sized alternator (trailer-towing package?), there isn't a lot of surplus current to charge outside batteries. Say, maybe 10 to 25 amps over standard jumper cables. So replacing 60Ah in the camp batteries would take several (2 to 6) hours of idling the car to avoid just transferring the car's starting battery charge to your camp batteries, such that your car won't start when it's time to leave. Less risk if you keep all accessories off when doing this (i.e., no current wasted to the lights, windshield wipers, etc.) because there would be more surplus current available.

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Re: Betteries, Batteries, Batteries Oh My!

Post by digital » Wed Mar 25, 2015 12:35 pm

One additional suggestion on the panel: Spend the few extra bucks for monocrystalline cells. There is a significant increase in efficiency over polycrystalline cells.

Last year I used the bundle mono set from that huge online river store. 100w. Complete kit: cells + 30A charge controller w/ cables < $200.

Worked great with a pair of deep cycle batteries.

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Re: Betteries, Batteries, Batteries Oh My!

Post by MFOB » Wed Mar 25, 2015 12:43 pm

apavlin wrote:
MFOB wrote:
Just_Joe wrote:I've never done it but the Captain's jumper cable suggestion would send a lot more amps to the battery in a much shorter time, and cost a helluvalot less $.
Sounds reasonable.

How many amps would a jumper cable deliver from the car?
Note that the Captain's advice about jump-charging your battery bank from your vehicle is perfectly valid. But it requires opening your vehicle (more dust!) and uses up more of your fuel (a car is an inefficient battery charger, because the battery charging alternator is a secondary load on the engine after the primary load of propelling the vehicle, therefore the car is not optimized for fuel efficiency when just charging). So, you could avoid the extra solar capacity for non-sunny days and use the vehicle to make up the charging shortfalls. Just don't let the batteries get flat-lined, or they won't hold a charge from any source (vehicle or solar).

Also, look at the charging time. A car alternator is sized to carry the normal electric load of the car (ignition, radio, lights, windshield wipers, A/C, etc.) plus a small surplus to recharge the car battery for the high-current but very-short-time load of starting the engine (only a few seconds, not hours, of cranking the starter). Therefore, unless your vehicle has a non-standard over-sized alternator (trailer-towing package?), there isn't a lot of surplus current to charge outside batteries. Say, maybe 10 to 25 amps over standard jumper cables. So replacing 60Ah in the camp batteries would take several (2 to 6) hours of idling the car to avoid just transferring the car's starting battery charge to your camp batteries, such that your car won't start when it's time to leave. Less risk if you keep all accessories off when doing this (i.e., no current wasted to the lights, windshield wipers, etc.) because there would be more surplus current available.
I figured 1/2hour or so wouldn't be bad. But 2-6. No deals. HondaEU2000 Here I come!
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Re: Betteries, Batteries, Batteries Oh My!

Post by mooserider » Wed Mar 25, 2015 12:52 pm

MFOB wrote:I figured 1/2hour or so wouldn't be bad. But 2-6. No deals. HondaEU2000 Here I come!
Note that charging batteries off a portable generator is still limited by the amount of current the battery charger can deliver, regardless of whether it's built into the generator or a separate plugged-in AC-powered charger. Example: If you only have a 20ampere charger, you'll only get 20Ah (or 240 watt-hours) (minus losses) into the battery per hour of generator run, regardless of how many thousands of watts the generator can deliver. But if you're going to run the generator for part of the day or evening for some other reason, no reason not to grab a few extra watts and recharge your batteries while you're at it.

But batteries are nice for power; they're QUIET! :D

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Re: Betteries, Batteries, Batteries Oh My!

Post by mooserider » Wed Mar 25, 2015 12:58 pm

Also note, those car charging estimates I made were assuming:

(a) the numbers from my original solar formula example for battery discharging, and

(b) all accessories on to minimize surplus current from the car's alternator. Things like headlights and air conditioners draw a lot of amps from the alternator, so turning them off significantly increases your available charging current.

You can get away with cheating on this for a couple of days, but doing it every day for a week without sufficient charge time would flatten your car battery (or sillier yet, be topping off your car battery from the solar charge on the half-dead camp batteries).

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Re: Betteries, Batteries, Batteries Oh My!

Post by LowePro » Wed Mar 25, 2015 1:08 pm

I used to try to do all the math, but then I decided I was overthinking it. (I'm not an engineer and I like the KISS principle). Decided to use the largest solar panel I could reasonably afford, store, and transport. Found a 32W panel that fit the bill. It does fine for me to run a swamp cooler, charge my camera 2 or 3 times per week, and run some LED lights in my trailer at night with a 110AH deep cycle battery. It does get sluggish by Day 8 and I'm pretty conservative with my power, FYI. My setup is just for 1 camper trailer, not for a whole camp or hangout space at night.

The math whizzes are more accurate than me, but generally get the biggest one that's feasible for you, keeping in mind that it won't actually behave exactly as the equations say it should. There are some tips to make sure your solar panel is working effectively, such as: angle one edge of the panel ~20 degrees up, and aim the face of the panel toward the south. This maximizes daily exposure for the latitude at BRCity. You can lean the panel on a piece of scrap wood for example. Keep the panel as cool as feasible, ie don't put it on the roof of a black car, and let some airflow under it (again leaning on a piece of lumber helps). And wipe the dust off with a wet rag once a day.

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Re: Betteries, Batteries, Batteries Oh My!

Post by MFOB » Wed Mar 25, 2015 3:14 pm

asr9754 wrote:I used to try to do all the math, but then I decided I was overthinking it. (I'm not an engineer and I like the KISS principle). Decided to use the largest solar panel I could reasonably afford, store, and transport. Found a 32W panel that fit the bill. It does fine for me to run a swamp cooler, charge my camera 2 or 3 times per week, and run some LED lights in my trailer at night with a 110AH deep cycle battery. It does get sluggish by Day 8 and I'm pretty conservative with my power, FYI. My setup is just for 1 camper trailer, not for a whole camp or hangout space at night.

The math whizzes are more accurate than me, but generally get the biggest one that's feasible for you, keeping in mind that it won't actually behave exactly as the equations say it should. There are some tips to make sure your solar panel is working effectively, such as: angle one edge of the panel ~20 degrees up, and aim the face of the panel toward the south. This maximizes daily exposure for the latitude at BRCity. You can lean the panel on a piece of scrap wood for example. Keep the panel as cool as feasible, ie don't put it on the roof of a black car, and let some airflow under it (again leaning on a piece of lumber helps). And wipe the dust off with a wet rag once a day.
True deal. I use the top of the yurt roof for the angle and then do the math to find the best heading to place it for maximum efficiency, move the yurt as necessary. I also just need this for just about what you're saying. Lights for the yurt, walkway, swampy, and a few charges is all.

I have gathered form the above posts and have came to the conclusions as noted:
a. Get as big of panel as I can get. More doesn't hurt as long as I have a good controller.
b. I sure as hell wouldn't use the truck to charge the batty back up. Too much inefficiencies and fuel wasted.
c. A generator is just too much, and I don't own and probably wont be purchasing one.
d. Wipe it off.

So, now onto Inverters. Last year I had a crappy SP and a inverter. The reason I'm asking all this is because I didn't own them, and they are not returning to the playa this year.

Good Brands?
Max Wattage?

Thanks for all the feedback so far. learned a lot from all of ya, esp. apavlin. Thanks again!
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Re: Betteries, Batteries, Batteries Oh My!

Post by FIGJAM » Wed Mar 25, 2015 3:21 pm

Here's the deal on recharging with cables.

Run the jumpers from the car battery to the battery you want to charge, but don't start the car right away.

Leave it this way for an hour.

This causes the batteries to "balance" so that when you start the car, the alternator will detect the low charge on both batteries an throw the maximum amps to the batteries.

On my stock chevy truck this is 40 amps.

I idle for an hour which gets the batteries up to 80% charge.

The last 20% has to be at a lower rate of charge and the alternator adjusts for this.

80% is plenty, so don't waste fuel going for 100% charge.

At idle with no load on the engine, the fuel consumption is about 1 and 1/2 gallons for the hour. 8)
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Re: Betteries, Batteries, Batteries Oh My!

Post by ygmir » Wed Mar 25, 2015 3:35 pm

FIGJAM wrote:Here's the deal on recharging with cables.

Run the jumpers from the car battery to the battery you want to charge, but don't start the car right away.

Leave it this way for an hour.

This causes the batteries to "balance" so that when you start the car, the alternator will detect the low charge on both batteries an throw the maximum amps to the batteries.

On my stock chevy truck this is 40 amps.

I idle for an hour which gets the batteries up to 80% charge.

The last 20% has to be at a lower rate of charge and the alternator adjusts for this.

80% is plenty, so don't waste fuel going for 100% charge.

At idle with no load on the engine, the fuel consumption is about 1 and 1/2 gallons for the hour. 8)
and make sure your jumper cables are large enough gauge to handle the current without loss, or much of it.
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Re: Betteries, Batteries, Batteries Oh My!

Post by some seeing eye » Wed Mar 25, 2015 3:41 pm

Burners are known for their frugality, aka cash-out efficiency. It is a sport to get the cheapest of any BM stuffs.

But let me make a proposal. Buy American-manufactured solar panels for Burning Man.

Unlike a home where one might buy 10's of thousands of dollars in panels, most burners are going to be buying less than $500 in panels. You can afford to buy American cells assembled in America. Not main China cells finished in Taiwan and maybe assembled in the US.

Should you decide to do so, find out where the cell was made, where the conducting layer was applied, where it was cut and where the edge and weather coating were assembled. There are even Asian and European HQ companies who do all of that in the USA with USA workers.

Your solar cells and batteries are a good home power outage backup strategy too!

I would be remiss to say visit the Alternative Energy Zone village for advice the year in advance, or use their message boards (which leave your email in the clear - use disposable) or consult local solar hobbyists.

(and there are plenty of solar electricity savvy participants on ePlaya and many threads to search)
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Re: Betteries, Batteries, Batteries Oh My!

Post by MFOB » Wed Mar 25, 2015 4:55 pm

Last year to power our Art we used Solar Panels form Black Rock Solar. Rented them for the week, for like 3-400 bones. At the end, they will sell them to you for $100 and give you your "deposit". I'm not sure how big (output)they are, but it recharged 3 Deep Cycle 110aH Battys and they ran lots of lights all night. Prolly 300W or so, maybe 500W about 3' x 5' in size. I know BRS is a good outfit, and trying to do good stuff so maybe a nice sized SP is they way to go from them.

I aint a cheap ass at all, but need a reasonably good deal. I don't want to buy shitty stuff. My theory is cry once now, or cry lots later. Meaning a bigger sum of $ up front hurts, but in the long run I wont have to fix/replace shit multiple times. For instance Tools at HF.

I would like to have a nice panel and something I can use not just on Playa but at my Cabin, Camping, Tailgating, etc....

Inverters, any words on those?
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Re: Betteries, Batteries, Batteries Oh My!

Post by [jim] » Wed Mar 25, 2015 6:28 pm

MFOB wrote: Inverters, any words on those?
This is how I broke down the different kinds of inverters available when I went searching:

fanless, temp-controlled fan, or fan-always-on: I could only find fanless inverters 150 watts or less. I like temp-controlled fan inverters as I keep my inverter in my living space, and keeping it on all night with its cooling fan buzzing and blowing... makes quite a racket (I used to camp in Hushville).

pure sine wave or not: some electronics, motors, etc are happier with pure sine wave AC than the 'modified sine wave' that most inverters put out. You can buy an inverter from HF; it will be modified sine, and see if your AC-powered stuff is happy with it (just return in 30?90? days). I compare sound/performance with the device plugged into the inverter vs plugged into the wall. If there's a difference... maybe you'd want to spring for pure sine wave (or bring a different less-picky appliance?)

Size: you'll have to do the math and see how much constant draw and peak draw you'll need. the inverter itself will consume an amp or more before it gives any AC, so you can add that to your battery depletion chart :cry: One of those kill-a-watt power meters can be used to see peak and average amps (I think they can, with a bit of math). Or you can use a clamp-on amp-meter to check amperages.

I used a harbor freight inverter for several years, but I could never get used to the noisy fan and smelly electronics. This year I have to bring some sensitive electronics so I upgraded to a pure sine wave.

I used the 'south american river' comments section for advice on which inverter might meet my needs.

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Re: Betteries, Batteries, Batteries Oh My!

Post by some seeing eye » Wed Mar 25, 2015 6:59 pm

Grid isolated - Burning Man - inverters are completely different from grid connected-grid synchronized inverters. If you want to use your solar system at home, like in a power outage, it is critical to understand the difference.

Why? Utility electrical workers could be electrocuted and die from a solar inverter feeding electricity into the grid connected to your home or business when there is a grid power outage in your neighborhood.

Yes Burning Man solar! Yes, understanding Watts, Amps, Volts, gauge!

Warranty period is a good measure of quality and longevity of an electronic product.

Connecting solar and inverters at home, Yes! Understanding safety, grid isolation/connection, critical.
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Re: Betteries, Batteries, Batteries Oh My!

Post by GreyCoyote » Wed Mar 25, 2015 7:27 pm

Just a quick point or two that may or not be useful:

1). The Honda EU-series have a 12-vdc outlet on them that will support 8 amps of charging current. This current comes off a completely separate winding in the machine and is isolated from anything else. With nothing else powered-up on the 120v side, these gennys will run in Eco Mode for 10+ hours on 0.9 gals of gas. That's enough to completely recharge the battery from any remotely reasonable discharge level. The only PROBLEM is, the EU's output is not voltage regulated and if it is left charging past the 100% charge point, this will cause the battery to outgas. So you need to either monitor the charge progress carefully, or use a cheapie charge controller ($25, or a bit more for an MPPT charger which is ideal), or just use a standard automatic 120v AC battery charger (very nice!).

2). Solar panels are now down around a buck per watt. If you look carefully, you can actually buy a 100+ watt panel for the SAME PRICE as a 25 watt panel. That 100 watt panel, with a decent MPPT charge controller, would totally rock and be the equivalent of charging with an EU2000... all for no noise or fuel hassles. Bump the panel size up a little, and you have something that will not only charge the battery quickly, it will have enough surplus to do other chores at the same time without causing the battery to fall off charge. IMHO, with solar, more is better, and too little is nearly useless.

Personally, if you want to go solar, I would go with a system that isn't task-specific to Burningman. I'd be inclined to buy a couple of large panels with the intention they could charge batteries that could power an inverter capable of keeping freezers on-line in case of a grid outage. Burningman would be a great test bed for this stuff and give you lots of seat time playing with it, but I would buy it and size it for "real-world" use if possible. :mrgreen:
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Re: Betteries, Batteries, Batteries Oh My!

Post by Major Krash » Wed Mar 25, 2015 7:28 pm

figure out what type of battery the Captain uses, then get one of those....during the week, as your battery runs down, just swap it out with one of the Captain's (who surely will be keeping them all topped off and all...)

:)
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Re: Betteries, Batteries, Batteries Oh My!

Post by maladroit » Wed Mar 25, 2015 11:16 pm

It's all a balance between cost, size, re-use, and capacity.

The hard fact is that you can only use the power that you have...so if you start using more power than your system can afford, you'll either decide what cutbacks to make or get used to the dark.

I have a hexayurt powered by a single 30 watt monocrystalline solar panel that I've had for about four years. I think it cost about 50-60 bucks and is about two feet tall. I made a folding mount that holds the charge controller and a deep cycle battery, and angles the panel at the exact angle needed for the playa's latitude:
Image

The system powers a 24/7 exhaust fan, a swamp cooler that runs 4-5 hours per day, about 12 watts of internal LED lighting (up to 2-3 hours per day), charging some devices (portable speakers etc), and a CPAP machine most nights. I took the battery to the playa fully charged and brought it home about 75% charged last year, which is pretty good...remember that you can use more power per day than your solar panel puts out, if it only has to last 7 to 10 days.

This has been a good set of compromises and features. I'd feel bad about using a 200W system only a couple weeks out of a year, not to mention the extra difficulty of transporting the panels and more batteries. This system cost under $150 and even if I had to completely replace all of it every five years, spending $30 per year to have the power available is acceptable. But it'll probably last a lot longer.

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Re: Betteries, Batteries, Batteries Oh My!

Post by Captain Goddammit » Thu Mar 26, 2015 12:33 am

In the case we're all talking about, the battery essentially lasted about half the week.
Nothing but a good pair of jumper cables and a little gas would work great, it sounds like it only needs charging once.
If you do this, FIGJAM's suggested method is great, and I'll add that using two or even three sets of jumper cables at once will deliver more current and reduce charging time. Use 2-gauge jumper cables or better. Not those cheapie rip-off ones that are small wires with a half inch thick layer of plastic insulation so they LOOK big.

It still sounds like just bringing another battery would be simplest, in this particular case.
$100, no noise, no dealing with anything.

If your power requirements are going up from last time, then you will want to look into more expensive solutions.

GreyCoyote brought up a good point about battery charging with Honda (or similar) generators. You will want to bring a large capacity battery charger plugged into the generator's AC output. The built-in charging circuit is weak and unregulated.
GreyCoyote: "At this rate it wont be long before he is Admiral Fukkit."

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Re: Betteries, Batteries, Batteries Oh My!

Post by BAK3R » Sat Mar 28, 2015 8:33 pm

As mentioned earlier, come by the AEZ and sign up for our solar tour (starts @ 11 under the AEZ sign). It's an hour long tour through the village. You will learn a lot and meet amazing people with all the knowledge you will ever want.

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Re: Betteries, Batteries, Batteries Oh My!

Post by incandenza » Sat May 30, 2015 8:54 pm

maladroit: just curious - how does the 5-gallon bucket do cooling your yurt? what kind of fan are you running on top of it?

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Re: Betteries, Batteries, Batteries Oh My!

Post by maladroit » Sat May 30, 2015 11:45 pm

It's a similar fan to what FIGJAM recommends, not quite the same model number but I already had it around. It will never actually make the hexayurt cold (have an H12), but it keeps it from becoming an oven. Since heat rises, the cooler air near the floor of the hexayurt means you can get some sleep any time of day. So it's still worth the hassle of bringing the cooler and budgeting water for it. I have a 12" PC fan as an auxiliary ceiling vent, it also doesn't do very much but gets some of the hottest air out of the roof area.

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