Please Help me create a “solar generator” that will fit my camping needs.

[sunnyand32]

I have been lurking here for some time, and would like some help in both fact checking my work and selecting the correct components to make this happen. If at the end of my research this is too expensive, I will just go and purchase one of the commercially available products, but I can’t help shake the feeling that if I build it myself I will end up with better components and maybe a better price than the commercial units.

I have been noodling building my own battery in a box that will allow my family to go camping with some power. My original goal was to be able to recharge all the phones, run 3 - 3watt led lights for 4 hours a night, and run a 12 volt fan for a few hours. After using a kill-a-watt to measure the amp-hours I need each day, I am rethinking the fan, since it is a power hog compared to the electronics and lights.

Power estimate – I believe I will need 5 AH per day to power the electronics and the lights. The fan will take 8.5 AH per day. I would like your help in picking the right battery, charge controller, input/output readout (not required but nice to have if it doesn’t cost too much), and connections.

To recharge the battery I want to plug it in to the wall outlet at home, and when camping we have a Brunton 26 watt solar panel that can be used to replace some of the power we are using. My estimate is that we can replace 3.2 AH per day from the solar panel. That means that we have a deficit of at least 1.8 AH when not using a fan, and 9.4AH when using the fan.

The longest we are camping is 7 days, but I would like to target 10 days to have a safety margin. After reading about batteries I would think that I need to get a battery sized to double my 10 day power requirement to avoid over discharging the battery. (can I go smaller or is this a reasonable assumption?) I am also considering using an AGM battery since it will be transported over some rough terrain.

Using the 50% idea, I would need a 36 AH battery if I don’t use the fan, or a 180 AH battery if I do.
Not sure what type of charge controller I should be looking at since I want to leave this plugged in when at home and solar when camping.
Not sure what brand/type of 12v battery I should be looking for, don’t want to break the bank but this isn’t life saving or anything, and with so few cycles per year I think it will die of old age before the battery goes due to number of cycles.

Would like to monitor the input and output loads, but don’t know how to accomplish this or if it is even feasible for a reasonable cost.
For connections I am thinking of having 3 - 12volt auto receptacles for providing power to the goodies, not sure what type of transformer I need to provide power to recharge the batteries or if the charge controller handles this, and I was thinking of using an Anderson powerpole connector for the solar panel connection to the battery.
Anything else I am missing?

Thank you for your help in investigating this project.

[Mike90250]

12volt auto receptacles

Handy because lots of gear fits them, but poor contacts. For low power stuff, they should be OK.

So, if you did your math correctly, and you are happy with it, great. I'd not suggest a "brand" of battery, but I'll suggest a automotive style jumper pack. You may have to dig deeply thru it's specs to find out what size battery (most are about 20ah agm or gel) is in it. But they have decent packaging and a carry handle. And a matching AC charger. I use one for my CPAP machine. I looked for a while to find one without an air compressor in it. And you can charge from the solar panel, it's so small, it won't hurt the battery pack.

[jony101]

Me if I was going camping for 10 days, I would need a minimum 100 watt panel, and at least 75 ah battery. And with that I would be roughing it. If you got room in the roof of your vehicule, it not hard to bolt a panel up there. You can run your fan all day long with that panel.

My first solar project was putting a 120 watt panel on the roof of my small astrovan, it produce about 6 amps of charging power. Enough to power a 12 volt fridge 24/7 plus charge my laptops and cellphones run lights and fans. It barely got the job done. Cost me 160 for panel, 75 dollars for a 75 ah agm battery and 20 dollars for the wincong pwm solar charge controller. It got me 100 percent off grid.

I later upgraded to a 240 watt panel (200 dollars used), ecoworthy 20 amp mppt controller (102 dollars) and 145 ah agm battery (125 dollars) . Now I have more power than I use, I get about 12 amps of charging power and can actually cook with this setup. I can run multiple fans all day long. I'm still using fluorescent lights. I never use a generator or shorepower.

One thing I learn is that you always use more power than you think. Cloudy days will ruin you calculations, thats why a somewhat large battery is required. The 26 watt solar panel you have is too small for camping, at most you can use it to charge cellphones. I recommend you get a large panel, as big as will fit on your roof. You wont regret it.

As far as connectors, I use to use powerpoles also, but now I use the xt60 connectors for all my 12 volt appliances, they handle 60 amps are small and easy to connect/disconnect. They work great on my powerhog which is a roadpro lunchbucket cooker (uses 11 amps). They cost about 8 dollars for 10 pair, only drawback is you need to solder the wires to them instead of crimping like the powerpoles. I avoid using 12 volt receptacles, I notice they all get hot especially when using fans that use 3 amps or more. For high power things like inverters I connect directly to the battery with thick gauge wire.

To measure voltage/amps use, you can get a dc wattmeter (they cost about 15 dollars on ebay) , you can connect from the battery to whatever load you have and it will measure the amps use and keeps a running track of how long its plugged in, it also measures peak amps for motors. You can also connect from solar controller to the battery and it will tell you how much amps your solar panel produce that day. Very easy to use and accurate.

[sunnyand32]

Jony and Mike,

Thanks for replying.

Jony, the connectors sound great, I will take a look at those, soldering is not a problem (although mine are probably not the prettiest they work). I hadn't thought about needing that much panel, I will have to rethink that part of the plan.

Will the charge controller let you plug in line power?

[Mike90250]

......
Will the charge controller let you plug in line power?

No, Solar or wind charge controllers are only for specific DC ranges. Small (less than 20A) controllers work up to about 75V panels, large ones generally to 150V PV panels produce DC voltage.

If you have AC line power, 12V & 24v battery chargers are common, above 24V, they become specialty items, like chargers for golf carts and forklifts.

[PNjunction]

The biggest problem here is that while your calculations are fine, they don't take into account solar insolation hours. I propose an alternative way of looking at it.

That is, the amount of usable hours for charging depends on where you are going, and what time of year. These solar-insolation hours are NOT like sunrise-to-sunset, but a much smaller window during the day. Local conditions, like tree shade where you are parked is another issue. I've gone down this road you have been on, and while it can be done, a much easier and more practical solution was found for low current needs.

Basically, I divided up the cellphone and led lights from the larger load requirements. So tackle that first. By far the easiest solution was to use small folding camping panels along with external batteries dedicated to each phone and given to family members. These are placed in the sun, and because they are small, they aren't relying on a battery back at the trailer that may NOT be getting a good charge depending on very short-distance conditions at the site. With small panels and external packs, they can be brought into patches of sunlight where they occur and taken care of that way.

What I'm talking about are handing out these Anker 14watt panels:
http://www.ianker.com/support-c7-g263.html

Instead of charging the phone directly in the hot sun, use external packs also from Anker like these Astro series to be charged first. Place them behind the panel out of direct sun.:
http://www.ianker.com/External-Batteries/category-c1-s1

If you get the batteries large enough, you don't need to achieve a full-charge, but can operate in what's known as "PSOC" or partial state of charge. Go about your business each day, but have a few of the panels and external batteries catching as much charge as they can. If you are operating usb-powered led lights, then a big one will take you through those hours you need. One reason I like Anker is that the build-quality is very good, and so are the cells. The "IQ" ports try to electrically configure whatever cable you have for the fastest charge. Some of my earlier solar charging was hampered by a cable only capable of small charge currents when the smartphone / device could actually handle more and charge in a faster time, but the cable limited it. The IQ port of the Anker figures it out in case your cable is funky.

If you want to monitor the voltage and current from those panels, search on Amazon for "USB Voltmeter" and you will come up with a bunch that show voltage and current while being inline. That way you can really tell if where you place the panels is doing any good, and also let you know when you are basically out of the solar-insolation window.

The other big advantage to this is from a theft / vandal standpoint. If you can operate from these, then you can lock them up in the camper or take them with you when hiking around and not worry about leaving a big panel unattended or having to dedicated a babysitter to them.

Running something like an Endless-Breeze dc fan like I do? I use the smallest Optima Yellow-Top, a D51 38ah battery. Much more convenient, easy to carry and rugged than a ups-style agm battery. And in a pinch, it makes it easy to install in a vehicle if you had to.

It can be easily charged with a simple setup like a 100 watt folding rigid panel from Samlex, or Renogy perhaps like this one:
http://www.samlexamerica.com/product...l.aspx?pid=536

If you don't want to go out with individual small 14 watt panels, you could just wire up a female cigarette lighter or two to the Optima, and use these DC > USB mobile adapters - again, Anker. Guess you can tell I like them - I'm hooked on the IQ ports.

http://www.ianker.com/Car-Chargers/category-c82-s1

While agm's don't need to be floated for long term storage at home, you still need to look in on them once every month or longer (depending on temperature) to give them a boost for the longest life. Most trickle chargers are actually BAD at this since they either wait for a major voltage drop to occur, or endlessly trickle when it is not really necessary.

About the smartest small charger that I'd recommend if you want to do long term storage that actually does what it says it does, and just as importantly, at the end of charge / floating is the Tecmate-Optimate 5 or 6. THAT is the only one I'd ever consider leaving on a flooded or even agm full time. I actually do and love what they do at the end of charge. It is also a way to ensure that you start out on the right foot before leaving on the trip, because they TEST the battery, show you results, and of course charge and maintain. Peace of mind.

http://www.tecmate-int.com/optimate6_detail.php

Due to the lack of solar-insolation hours of where you go and other variables, and your huge 10-day reserve requirement, I'd actually go this route and see how it goes. That way, if it doesn't pan out, you aren't stuck with a panel and a big battery just doing nothing in a corner of your garage. AND, these smaller items could of course be used by family members when not camping out with you.

[sunnyand32]

Thank you for such a well thought out answer to the same problem. This is why this forum is so great. I may have to rethink my approach. Glad I haven't spent any money yet.

[thastinger]

Thank you for such a well thought out answer to the same problem. This is why this forum is so great. I may have to rethink my approach. Glad I haven't spent any money yet.

Why do you need the solar stuff at all? Why not bring along a couple of 100AH marine/RV batteries and buy a decent small PSW inverter that has USB outputs as well then just recharge the batteries when you get back home? If you ever needed to recharge one of the 100AH batteries during the camping trip just throw some jumper cables on it and use the vehicle to charge it.

[solarsam12345]

in my opinion

Lets say the fan took 30w and the LED's and things are 25w 30*4=120 and 25*3=75
120+75=195wh or 0.195kwh. A 34ah battery wh= v*ah*0.4
Battery wh= 12*34*0.4=163. Therefor the battery wouldn't be sufficient.
A 50ah battery= 12*50*0.4=240wh, this is sufficient for one day of no sun.

For 4 days of no sun that would keen you would need around 200ah of battery capacity
My recommendation would be a 110ah deep cycle battery.

For the solar panel if you got equivalent to 4h of direct sun:
Lets say you need to recover from 2 days of no sun that would equal 400wh
400/4=100w of solar

For losses and safety you would upscale by 30% so that is 130w of solar

So from my calculations you would need a 110ah deep cycle battery, 15a charge controller and a 130w solar array.
I'm a beginner so I may be wrong but I would go for that even though you could get by on 1/2 the system size if you got guaranteed sun every day

From Sam

PS: to charge the battery at home get a 12v 12amp smart charger. That would charge a 100ah battery in around 10 hours and maintain them

[ArchAngel72]

Ok for quick and simple no sweating putting it together and really easy use

Check out Goal Zero's products for camping I think they are very nice

[russ]

Ok for quick and simple no sweating putting it together and really easy use

Check out Goal Zero's products for camping I think they are very nice

Goal Zero - expensive for what you get and their web site glosses over a lot.

[ArchAngel72]

Goal Zero - expensive for what you get and their web site glosses over a lot.

I admit Im a fanboy... I also did not realize that this was such an old post my appologies for drudging it up.

As for cost yep I agree however If more people purchase product quality and price may come down. also it keeps a "solar" company in business

As for glossing can you describe what you mean to me in a mesage.. not here on the board please

[MagicMikeJ]

size of fridge

Me if I was going camping for 10 days, I would need a minimum 100 watt panel, and at least 75 ah battery. And with that I would be roughing it. If you got room in the roof of your vehicule, it not hard to bolt a panel up there. You can run your fan all day long with that panel.

My first solar project was putting a 120 watt panel on the roof of my small astrovan, it produce about 6 amps of charging power. Enough to power a 12 volt fridge 24/7 plus charge my laptops and cellphones run lights and fans. It barely got the job done. Cost me 160 for panel, 75 dollars for a 75 ah agm battery and 20 dollars for the wincong pwm solar charge controller. It got me 100 percent off grid.

I know this is an old post, but one never knows..... what size fridge was that?? Your setup was basically what I want to achieve.

[nomadh]

I have a camping system I put together 2 years ago. We started with one of those car jumper packs and the good duracel one we had lasted maybe 3 or 4 years and I think was used when we got it and we didnt maintain it properly. A few other no names never did so well. So 3 trips ago I bought a used mobility scooter battery. I think it was for $40 or so. It did a great job for charging gameboys and cell phones and a touch of laptop and the portable dvd for nighttime movies for a camp of about 15 people. I charged it maybe 2 times during the week for a few hours from the bathroom socket but It might have made it all week without. So a year ago I bought a 100w panel and a charge controller for about $150. Testing shows it works great. The biggest problem with the panel is all the shade from trees. To really get a good charge in a nice wooded campsite requires maybe 15 panel moves a day. We settled on about 4 moves a day as there was at least someone around a few times a day to adjust. We didnt do a lot of measuring but we never ran out of juice the 2 times we used it. Sorry it wasn't very scientific but I was on vacation
I would suggest one possible change. Instead of our 1 big panel I with I got 2 smaller ones and a charge controller that could handle that. Easier to pack in the car and aim the panels different ways and work it like a microinverter system.