# Charging a car battery via a solar panel



## lightseeker2009 (Jun 6, 2013)

Hi everyone.I want to keep a car battery at my camping site. I will use it at most once a week and will tap at most 30 to 40 amps out of it.What is the minimum size solar panel that will put back this amount of power into the car battery over a period of 6 days?What controller will be needed?


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## jasonck08 (Jun 6, 2013)

lightseeker2009 said:


> Hi everyone.I want to keep a car battery at my camping site. I will use it at most once a week and will tap at most 30 to 40 amps out of it.What is the minimum size solar panel that will put back this amount of power into the car battery over a period of 6 days?What controller will be needed?



First off, car batteries are NOT designed to be deep discharged. You will want a deep cycle marine battery if you want to pull 30-40Ah out of it. Car batteries are designed to be charged almost constantly, and very shallow partial cycles.

By 30-40 amps, I assume you mean amp hours?

If so, 30-40 * 12 = 360-480Whrs.

8hrs of sunlight * 6 days = 48hrs of sunlight

360/48 = 7.5W and 480/48 = 10W.

So assuming 100% Charge efficiency 7.5-10W would be enough. But you should probably go with 15-20W.

Some 12v solar panels can charge lead acid batteries directly, or you could get a charge controller (don't know specific model #'s).


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## SemiMan (Jun 6, 2013)

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## TinderBox (UK) (Jun 6, 2013)

I only have a 14watt panel, but the guide says you should use an 7amp battery, so for a 60amp battery, get a 120watt solar panel minimum.

John.


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## jasonck08 (Jun 7, 2013)

SemiMan said:


> No offense to jasonck08, but with the exception of car batteries not liking to be discharge very much, which is true, most of the rest of the post is not accurate.
> 
> It is a common misnomer that hours of sunlight = hours of solar energy. That would only be true under perfect conditions and with perfect tracking of the solar panel with the sun. Realistically you will not have perfectly clear skies and you are likely going to have a stationary panel. Hopefully you will not have any shade. If you do, that changes everything!
> 
> ...



Uhhh... Thanks for the condescending response. The information I provided is accurate, yet you suggest disregarding everything.  I did not say that hours of sunlight = hours of energy. Days during the summer are 14+ hours long in some places... ~8 peak hours is fairly common on a long summer day in some locations... http://www.pveducation.org It obviously depends on the environment. Where I live we get the 2nd most sunlight out of any city in the US.

Also I see you mentioned he is in California, but I don't see any information in his post for that. Where did you get that information from? Or are you confused, and saw my location, instead of his?



TinderBox (UK) said:


> I only have a 14watt panel, but the guide says you should use an 7amp battery, so for a 60amp battery, get a 120watt solar panel minimum.
> 
> John.



I think that would be probably if you plan on using a lot of the batteries capacity every day. It sounds like the OP just needs a small panel to trickle charge the battery over the course of 6 days.


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## lightseeker2009 (Jun 7, 2013)

I want a panel that can charge the battery in 6 days


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## Knight_Light (Jun 7, 2013)

I have used solar extensively over the years. And the one thing that I have learned is that you always get the biggest panel that you can afford and physically accommodate (within reason). Spend money on a good controller.

If you have the budget you can go for foldable panels, they really pack down small. I would recommend a 60 W foldable. Here are the specs for something like that.
•Operating Voltage: 15.4
•Wattage: 60
•Current: 3.6 amps
•Width (mm): 1207 unfolded; 336 folded
•Length (mm): 1308 unfolded; 178 folded
•Width (in): 47.5 unfolded; 13.25 folded
•Length (in): 51.5 unfolded 7 folded
•Weight (kg): 1.45 kg
•Weight (lb): 3.19 lbs


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## AnAppleSnail (Jun 7, 2013)

Knight_Light said:


> (Folded panel)
> •Weight (kg): 1.45 kg
> •Weight (lb): 3.19 lbs



Urgh. I was just wondering why there is no folded and unfolded weight. Not enough coffee in the world...

Hours of sun in a campsite are usually much less than on a house rooftop. Most solar guides tend to assume that you are able to place the solar panels away from or above trees. I know that in dappled shade, my solar yard lights have about 1/10th the runtime of the ones in full sun. I do not know how things are in California, but a forested area in the mountains may have 12 (Peaktop) or 6 (Valley bottom) hours of sun in summer. This will be further cut by shade and imperfect panel aiming.

For what it's worth, a bigger solar panel (That you can afford, and that won't be stolen) will almost always make you happier than a smaller one. And if a $200 solar panel will make you 10x happier than a $100, maybe it's worth that jump. However, plan on a coulombic efficiency (Energy in vs. Energy Stored) of about 1.6 on the lead-acid battery. If your charge controller is 85% efficient, then:

"I want (40amp*hours x 12v)=500W*h per week."
"I need to put (500W*h * 1.6) = 800W*h in per week, or 120W*h per day."
"I need to gather (120/0.85) = 150 W*h per day for my charge controller."
"For my region I need to de-rate the solar panel's output by (x)."
"My good, strong sunlight there is (2, 4, 6, 8, 10) hours per day when I'll use this. That gives me the rate the panel should gather energy."


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## Knight_Light (Jun 7, 2013)

AnAppleSnail said:


> Urgh. I was just wondering why there is no folded and unfolded weight. Not enough coffee in the world....


 The folded weight is in kilograms and the unfolded weight is in pounds.


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## ChrisGarrett (Jun 7, 2013)

60w of goodness and I'm in Miami, so I get a lot of solar hours down here and I agree that most people assume too many S.H. when they're thinking things through. Unless you want to babysit your rig and I'm in a condo, bigger will be better because it will be faster, IMO. Together, those two 30w with hardware weigh in at ~2kg/11#, but moving up to the 40w panels, things start adding up, when dealing with rigids.

You can find the milspec, foldable 62w PowerFilms, but they're over $800 the last time I checked this past August. Rigids are heavier, but more durable, have longer warranties and those pictured above are mono-crystaline, so a bit more efficient than the polys and CIG/Thin Films portables.

Also, as semiman mentions, you have controller and charger inefficiencies, so you can never assume 100%. I don't think that my Morningstar SS-10L has a 30% loss, but I can see the controller and any of my battery chargers getting close to that number. Figure on 75% useful output when calculating this stuff and you should be close to reality.

Doing a SLA/AGM, you only have to deal with say...half of that number, becuase that Morningstar SS-10L IS a battery charger, but there's still going to be less than the full pie going in.

Also, the smaller controllers have certain limits to how big a battery they can charge and I don't think that they're meant to charge up a totally dead car-type battery, if I remember the manual correctly, so keep that thought in mind when putting something together.

Anyhow, it was a fun project to do and I think something like my rig, or a nice size foldable panel, are necessities where I live and I'll be waiting during this hurricane season, but I'll be ready!

Chris


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## Knight_Light (Jun 7, 2013)

ChrisGarrett said:


> 60w of goodness and I'm in Miami, so I get a lot of solar hours down here and I agree that most people assume too many S.H. when they're thinking things through. Unless you want to babysit your rig and I'm in a condo, bigger will be better because it will be faster, IMO. Together, those two 30w with hardware weigh in at ~2kg/11#, but moving up to the 40w panels, things start adding up, when dealing with rigids.


 
Let me start by saying that you have a sweet set up. :thumbsup:



ChrisGarrett said:


> You can find the milspec, foldable 62w PowerFilms, but they're over $800 the last time I checked this past August. Rigids are heavier, but more durable, have longer warranties and those pictured above are mono-crystaline, so a bit more efficient than the polys and CIG/Thin Films portables.


 
I agree with your more efficient comment but I don’t really agree with durability. In my opinion the PowerFilms foldable will be a lot more durable if you are constantly moving your set up around. I have seen rigid panels get damaged in transportation. Now if you go to the PowerFilms rollable then you are totally dealing with an almost indestructible product when comparing to rigid mono-crystaline panels.



ChrisGarrett said:


> Also, the smaller controllers have certain limits to how big a battery they can charge and I don't think that they're meant to charge up a totally dead car-type battery, if I remember the manual correctly, so keep that thought in mind when putting something together.


 
Smaller charge controllers won’t be able to handle large current but as long as you stay within their specifications they will theoretically be able to charge any capacity 12V battery. Plus don’t forget that Pb doesn’t require a lot of current to charge. Now they may miss termination on a car battery but you can always follow the progress with a meter.


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## ChrisGarrett (Jun 7, 2013)

Knight_Light said:


> I agree with your more efficient comment but I don’t really agree with durability. In my opinion the PowerFilms foldable will be a lot more durable if you are constantly moving your set up around. I have seen rigid panels get damaged in transportation. Now if you go to the PowerFilms rollable then you are totally dealing with an almost indestructible product when comparing to rigid mono-crystaline panels.



I did extensive research on the rollable/foldable solar chargers last August: Brunton, Global Solar Sunique, Goal Zero and Powerfilm. All had either 3 year, or 2 year warranties, in the case of Brunton (IIRC).

The reason for this is that the thin wiring between the cells are not all that durable over the constant folding/rolling cycling that they encounter and they break sooner, rather than later.

Rigid panels have glass and glass breaks, but their warranties are usually 10 yrs at 90% rated output and 25 years at 80%.

Since I only have those two rigid panels, I can't comment on the longevity of the portables, but the warranties aren't all that long, if you look into them and that's done for valid reasons, I"d assume?

Chris


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## IonicBond (Jun 8, 2013)

lightseeker2009 said:


> Hi everyone.I want to keep a car battery at my camping site.


Unless you are rich and are willing to trash an SLI (starter, lights, ignition) battery very fast with those deep discharges, then you'll need at least a hybrid dual-purpose marine battery. You don't mention if you are actually intending to start a car with it when you are done. Are you?



> I will use it at most once a week and will tap at most 30 to 40 amps out of it.


That means that you'll have to have at least DOUBLE that in overall capacity, (50% SOC after discharge - any further damages the battery, and some gear will not run well under 12v when you have reached that 50% SOC). Get the 20-hour discharge rate. If all you have is the "RC" rating, then multiply that by .6 to get in the ballpark at 80ah or more.



> What is the minimum size solar panel that will put back this amount of power into the car battery over a period of 6 days?


Bad idea using maintenance charge levels of current to actually charge, especially longer than a period of 2 days max. All the time that you are below a full charge, the battery will be sulfating almost as much as it is getting recharged. In addition, a deep discharge really means that you need at a minimum C/12 to about C/8 to *really* charge, and not just put a superficial surface charge on the battery with a dinky little panel or maintainer.

As for recharging fast enough to avoid sulfation (the natural process that all LA batteries do when not fully charged), plan on no more than 2 days to get it done from a 50% SOC. Otherwise you'll be "walking down" the capacity faster than you know it by not providing a decent charge level. (stratification, along with sulfation plays a part here also if we're still talking a wet-cell, and not something like a sealed AGM.

How FAST are you trying to pull that 30-40 amps? A minute - an hour, a few days? Also what is actually your load and how are you powering it? Are you running nothing but 12v gear, or are you using inverters (msw or psw?) and are those loads inductive motors that might trip your inverters no matter what?

Realistically, we also don't know your location which will help determine your solar-insolation hours. These are different from just visible daylight hours. A simple example is that solar insolation means that the sun is strong enough to actually do some good and get the rated output from your panels - typically between the hours of 10a to 2pm - but this varies depending on your location.

Search for "solar insolation chart". Some governmental charts may be hard to read, whereas some solar vendors have easier to read charts where you look up your city, and can find the high summer, low winter, and average hours. If you want to give yourself some headroom, use the low winter values.

Let's assume you have 4 hours of solar insolation in the summer. With a 2-day maximum, that means 8 hours available for charging. To replenish 40ah, at first one might think they would need an 80watt 12vdc nominal panel that puts out about 4.5a at best. BUT, chargng is not totally efficient, so lets add 15% to that. Somewhere between a 100 to 120 watt panel with a 10a Morningstar pwm controller on an 80ah approx hybrid marine battery would be my first starting point assuming that much solar insolation is actually available for a 2 day charge.


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## Knight_Light (Jun 8, 2013)

ChrisGarrett said:


> I did extensive research on the rollable/foldable solar chargers last August: Brunton, Global Solar Sunique, Goal Zero and Powerfilm. All had either 3 year, or 2 year warranties, in the case of Brunton (IIRC).
> 
> The reason for this is that the thin wiring between the cells are not all that durable over the constant folding/rolling cycling that they encounter and they break sooner, rather than later.
> 
> ...


Chris not only am I familiar with the companies that you listed but I have actually used products from most of them. These foldable panels are not as flimsy as you may think. And with a little bit of tinkering you can make them a lot stronger. Now if you are talking about the rollable PowerFilm those are encased in some sort of material (almost like a laminate/epoxy)and are very rugged. I’ve seen numerous holes punched right through them and they still work.

And you are comparing apples and oranges. Without a doubt if you have a stationary nonremovable set up, the rigid panels are the way to go. But if you have a mobile solution then they are not as durable as you think. And I guarantee you if you broke the panels by stepping on them dropping them or whatever that 20 year warranty would not cover it.


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## ChrisGarrett (Jun 8, 2013)

Knight_Light said:


> Chris not only am I familiar with the companies that you listed but I have actually used products from most of them. These foldable panels are not as flimsy as you may think. And with a little bit of tinkering you can make them a lot stronger. Now if you are talking about the rollable PowerFilm those are encased in some sort of material (almost like a laminate/epoxy)and are very rugged. I’ve seen numerous holes punched right through them and they still work.
> 
> And you are comparing apples and oranges. Without a doubt if you have a stationary nonremovable set up, the rigid panels are the way to go. But if you have a mobile solution then they are not as durable as you think. And I guarantee you if you broke the panels by stepping on them dropping them or whatever that 20 year warranty would not cover it.



I specifically mentioned that the warranties on all four brands are three years or less. That tells me something, doesn't it? Sure, people can mod things left and right and improve on them, no doubt, but the foldable panels don't have the warranty that the rigids have, if both are used normally and as intended.

Nobody's expecting me to get warranty service on my rigids if I drop one of them on my way down the stairs.

Those warranties are kind of short and the companies are doing that for a reason, don't you think?

Whether the foldables end up working well past those three (or two) years, I can't say, as I went with the rigid setup, but those warranties were part of the reason I didn't pull the trigger on a PF 30w panel...it was just too short for me at that price.

Now, to be fair to myself, I wouldn't be folding and unfolding it all that much, so those wires wouldn't get abused, as they would if I were out in the field using the panel everyday.

Chris


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## Knight_Light (Jun 8, 2013)

ChrisGarrett said:


> I specifically mentioned that the warranties on all four brands are three years or less. That tells me something, doesn't it? Sure, people can mod things left and right and improve on them, no doubt, but the foldable panels don't have the warranty that the rigids have, if both are used normally and as intended.


 
The key phrase here is “used normally and as intended”, but the rigid panels have a different use and intention then the foldable panels. So you are comparing apples and oranges.



ChrisGarrett said:


> Nobody's expecting me to get warranty service on my rigids if I drop one of them on my way down the stairs.


So then you have to ask yourself a question. If you use them under the intended conditions that the foldable and rollup panels would be utilized how long would they last?



ChrisGarrett said:


> Those warranties are kind of short and the companies are doing that for a reason, don't you think?


 
Because their intended purpose is a harsher environment therefore their lifetime will probably be shorter. Again apples and oranges


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## SemiMan (Jun 8, 2013)

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## SemiMan (Jun 8, 2013)

ChrisGarrett said:


> 60w of goodness and I'm in Miami, so I get a lot of solar hours down here and I agree that most people assume too many S.H. when they're thinking things through. Unless you want to babysit your rig and I'm in a condo, bigger will be better because it will be faster, IMO. Together, those two 30w with hardware weigh in at ~2kg/11#, but moving up to the 40w panels, things start adding up, when dealing with rigids.
> 
> You can find the milspec, foldable 62w PowerFilms, but they're over $800 the last time I checked this past August. Rigids are heavier, but more durable, have longer warranties and those pictured above are mono-crystaline, so a bit more efficient than the polys and CIG/Thin Films portables.
> 
> ...




30% loss that I mentioned is due to the fact of voltage mismatch between the solar panel and the battery, a problem with all PWM controllers. Unavoidable without going with a MPPT controller.


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## SemiMan (Jun 8, 2013)

jasonck08 said:


> Uhhh... Thanks for the condescending response. The information I provided is accurate, yet you suggest disregarding everything.  I did not say that hours of sunlight = hours of energy. Days during the summer are 14+ hours long in some places... ~8 peak hours is fairly common on a long summer day in some locations... http://www.pveducation.org It obviously depends on the environment. Where I live we get the 2nd most sunlight out of any city in the US.
> 
> Also I see you mentioned he is in California, but I don't see any information in his post for that. Where did you get that information from? Or are you confused, and saw my location, instead of his?
> 
> ...





Sorry, but your response was not accurate, even for your location when one consider that not every day or week is perfect.

You can point me to PVEducation.org but I have years of doing this including resource modelling in must work situations not to mention having designed a high performance MPPT controller and putting up my systems in many locations.

If he went with your suggestion, the OP would have ended up with an undercharge and likely damaged battery.


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## SemiMan (Jun 8, 2013)

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## ChrisGarrett (Jun 8, 2013)

SemiMan said:


> 30% loss that I mentioned is due to the fact of voltage mismatch between the solar panel and the battery, a problem with all PWM controllers. Unavoidable without going with a MPPT controller.



Actually, I just did a little research and I found out that with smaller arrays such as my 60 watter, a MPPT controller might actually be less efficient than a good PWM controller, due to the increased computer processing power and other transitor dohickeys found in many MPPT controllers! They take more power to operate, is the theory and that is power that's not going into the battery (batteries).

I do see the 17.5v>14.5 volt issue that you mention, but as one link pointed out, that's 14.5/17.5 = .83, so in that case, it's 17%, whereas MPPTs are upwards of 92-95% with larger arrays.

Anyhow, thanks for your posts, as I enjoy reading and learning about this stuff.

Chris


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## Sub_Umbra (Jun 8, 2013)

ChrisGarrett said:


> ...Also, as semiman mentions, you have controller and charger inefficiencies, so you can never assume 100%. I don't think that my Morningstar SS-10L has a 30% loss, but I can see the controller and any of my battery chargers getting close to that number. Figure on 75% useful output when calculating this stuff and you should be close to reality.
> 
> Doing a SLA/AGM, you only have to deal with say...half of that number, becuase that Morningstar SS-10L IS a battery charger, but there's still going to be less than the full pie going in....



I love the Morningstar SS-10L but if you locate it more than 24" from your battery and don't use the largest cables that may be used with that unit you are hosing yourself_* and your battery.*_ 

This isn't Rocket Surgery.


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## ChrisGarrett (Jun 8, 2013)

Sub_Umbra said:


> I love the Morningstar SS-10L but if you locate it more than 24" from your battery and don't use the largest cables that may be used with that unit you are hosing yourself_* and your battery.*_
> 
> This isn't Rocket Surgery.



How does 12ga Vampire Wire CCC (continuous cast 'four nines' copper) audio grade wire, grab ya?

I'm only pushing at best, 3.5A through it from the panels, so I'm not too worried and I'm pretty much under 24", as well.

I think that you're exagerating a bit, but I understand some of the issues with having wiring that is too long.

Rock on bro.

Chris


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## SemiMan (Jun 9, 2013)

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## Rexlion (Jun 9, 2013)

With solar panel prices being so (relatively speaking) low nowadays, it doesn't make sense to go "minimum" wattage. I'd say get at least 40W, but 60W or 80W would be better. I recently bought a 75W panel from SolarBlvd for under $100, and a Morningstar PWM controller for about $25. Pretty affordable!


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## lightseeker2009 (Jun 10, 2013)

Thanks for all the advice and responces. 
I was asked what and how much at what time.
I only want to run a few lights. Ampdraw will be 7-8 amps at most. 5 hours max usage at a time, one night per weekend.

A generator might be a better, and cheaper option but they make so much noise. So much so that you will not sleep as good as you should. So it can only be used during the day. But I also thought about getting a fast charger in the 30 amp or so range. Then I can charge the battery in one or two hours with the generator in daylight hours.
Will such a fast charge on a weekly basis be bad for the battery? How fast can you charge a deep cycle battery and a normal car battery without shortening their lifespan?


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## Norm (Jun 10, 2013)

lightseeker2009 said:


> A generator might be a better, and cheaper option but they make so much noise.



A better and cheaper option may be charging batteries at home to take with you.

Norm


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## Knight_Light (Jun 10, 2013)

lightseeker2009 said:


> Will such a fast charge on a weekly basis be bad for the battery? How fast can you charge a deep cycle battery and a normal car battery without shortening their lifespan?


 
PB does not like to be charged fast. It depends on the discharge state of the battery but most smart car battery chargers will typically take 14 hours to do the job once it’s been discharged to a level where it will not start a car. As others have mentioned you might want to switch to a different format then a car battery.


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## SemiMan (Jun 10, 2013)

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## Poppy (Jun 10, 2013)

I found that a ceiling bounced xml emitter @ about 100 lumins, lights my kitchen fairly comfortably.
I believe that pretty much any 18650 XML light that is regulated to put out 200 lumins will do so for 5-7 hours depending upon the battery.

A handful of flashlights, and batteries may be all that you need, and you won't have to be concerned that your nice solar unit doesn't evolve to grow a set of legs during your week's absence.


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## lightseeker2009 (Jun 10, 2013)

Norm said:


> A better and cheaper option may be charging batteries at home to take with you.
> 
> Norm



Yes, but I like to travel as light as possible. The generator is allready there, just too noisy.

The camping spot is actually a fishing spot. It is very safe and not even things left outside gets stolen, touch wood.
I need this amount of light as a light is needed inside, under the roof, and at the spot on the yeti where the fishing is taking place. So 3 permanent lights are needed as a minimum. One is a 20 watt floodlight. The other two are 11 watt energy savers. I do take along at least 5 flashlights per trip. You know, you can never have enough


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## ChrisGarrett (Jun 10, 2013)

lightseeker2009 said:


> Yes, but I like to travel as light as possible. The generator is allready there, just too noisy.
> 
> The camping spot is actually a fishing spot. It is very safe and not even things left outside gets stolen, touch wood.
> I need this amount of light as a light is needed inside, under the roof, and at the spot on the yeti where the fishing is taking place. So 3 permanent lights are needed as a minimum. One is a 20 watt floodlight. The other two are 11 watt energy savers. I do take along at least 5 flashlights per trip. You know, you can never have enough



Go out and buy a mid quality rigid, 30-50w panel (like my Sopray 30w) for $90-$130 delivered, a pair of Y connectors for $15, a $70 Morningstar SS-10L and a couple of PowerSonic 18Ah scooter batteries for $75 shipped, all off of Ebay and see what you see. 

You're under $300 for a 50 watter and you've got a nice semi portable rig that you could bury in the sand when you leave. Throw a few more bucks at some 12vdc charger adapters, 12v fans, a 12v socket and you can charge stuff up and keep you cool as well!

Chris


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## SemiMan (Jun 10, 2013)

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## ChrisGarrett (Jun 10, 2013)

I've been looking at Concorde's Sun Xtender line of solar batteries. Their 690-T is a 69Ah battery that I can get for $219 shipped. Their 840-T (84Ah) is $300 shipped!

This is supposed to be a great brand, from my past research, but for my needs, those two 18Ah Power Sonics for $75 shipped, would be an easier pill to swallow.

Also, I bet rigid panels could be buried in the sand quite easily and survive!

Chris


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## Knight_Light (Jun 10, 2013)

ChrisGarrett said:


> I've been looking at Concorde's Sun Xtender line of solar batteries.


 I have used their batteries and was pleased. They make a good product.


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## SemiMan (Jun 11, 2013)

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## eco007 (Sep 20, 2013)

I also agree that car batteries are not designed to be deep discharged. You will want a deep cycle marine battery for longer use.


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## hopkins (Sep 21, 2013)

Was thinking of 2 ways to do this: the right way as expensive as possible
or the wrong way as cheap as possible. 

The cheapest: Nix wired electric lights and use some Walmart kerosene lanterns for illumination
Quiet, cheap and 100% reliable.

Most expensive: Buy a lot of solar with sun tracking pivots racks and
several deep cycle batteries and an off grid smart home
controller system with cell phone controller capability that ties
the solar and your generator into the battery bank
and fires it up on cloudy days. Also you can cell call your 
off grid camp controller system using the supplied app on your
smart phone before you arrive and get a staus report on the battery
bank and have the generator roar to life if needed to top them
off before the quiet fishing weekend begins.

But seriously any of the panel systems mentioned above will be fine. 
Adding another panel and or battery if you need more juice should be easy.


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## lightseeker2009 (Sep 22, 2013)

We ended up in buying a Honda generator. Very pricey, but very quiet and reliable. 
Thanks for all the great advice. I believe I have made the correct choice, as I need power not for lights only.


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## ChrisGarrett (Sep 23, 2013)

lightseeker2009 said:


> We ended up in buying a Honda generator. Very pricey, but very quiet and reliable.
> Thanks for all the great advice. I believe I have made the correct choice, as I need power not for lights only.



Can't go wrong with the Hondas, Yamahas or Robin-Subarus for smaller portable and quiet generators.

Chris


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## lightseeker2009 (Sep 23, 2013)

And I just wanted to cut out any and all complexity. Just start her up and plug in what you want. It might even work out cheaper than batteries, solar panels and inverters. Granted, it is not as quiet at an inverter would have been, but it is not loud at all.


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## SemiMan (Sep 23, 2013)

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## lightseeker2009 (Sep 24, 2013)

100% agreed.
That is why we paid so much for a Honda. The generator will be run inside a shed, reducing a lot of the noise. My father must sleep with one of those machines CPAP, I believe. They draw a lot of power, hence the choice to rather get a generator. When our neighbor is there, I don't sleep there. His generator is the noisiest piece of junk ever built. He refuses to use the gas option for his fridge. So I will not be bothering him, rather the other way around


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## Norm (Sep 24, 2013)

lightseeker2009 said:


> The generator will be run inside a shed


Carbon Monoxide ????

Norm


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## lightseeker2009 (Sep 28, 2013)

Nobody will be sleeping in there. That shed is just storage space.

But we found that running the generator outside made the noise even less than running it inside. 
My only criticism with this particular generator is the small fuel tank. They should make it large enough to last at least 6 to 7 hours, ie a full night. It is not good enough for what we need it.


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## engineeringnerd (Mar 6, 2015)

This isn't true anymore. New solar panels are very efficient. I have a small 1.5 watt solar panel that I bought from harbor freight that puts out around 17 volts even with heavy overcast. I added a toggle switch to cut it off at night to prevent reverse drain. You could use a diode to prevent reverse drain at night but it's gonna cost you about 3/10ths of a volt. I have a BMW X5 with tons of electronics - Nav, 360 degree radar, front and rear cameras each with dedicated screens, GPS tracker and other goodies. I'm in school most of the day so it gets a good 6 hours or so to charge which is plenty. The alternator picks up where the solar panel leaves off. 






SemiMan said:


> No offense to jasonck08, but with the exception of car batteries not liking to be discharge very much, which is true, most of the rest of the post is not accurate.
> 
> It is a common misnomer that hours of sunlight = hours of solar energy. That would only be true under perfect conditions and with perfect tracking of the solar panel with the sun. Realistically you will not have perfectly clear skies and you are likely going to have a stationary panel. Hopefully you will not have any shade. If you do, that changes everything!
> 
> ...


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## SemiMan (Mar 7, 2015)

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## Keisari (Mar 8, 2015)

engineeringnerd said:


> This isn't true anymore. New solar panels are very efficient. I have a small 1.5 watt solar panel that I bought from harbor freight that puts out around 17 volts even with heavy overcast. I added a toggle switch to cut it off at night to prevent reverse drain. You could use a diode to prevent reverse drain at night but it's gonna cost you about 3/10ths of a volt. I have a BMW X5 with tons of electronics - Nav, 360 degree radar, front and rear cameras each with dedicated screens, GPS tracker and other goodies. I'm in school most of the day so it gets a good 6 hours or so to charge which is plenty. The alternator picks up where the solar panel leaves off.


Good for you, but your 1.5 watts nominal solar panel is probably not doing any good. Those actually produce way less in real life contitions. A 9 watt-hour charge is pretty much equal to zero in practical terms for a car battery when it has just been topped up by alternator power before and will be after the 6 hours. And again, there is no 9 watt-hour charge but much less in reality.

GPS, radars and other stuff that is used while driving does not drain the battery and does not affect the need for standby charging at all. Even the high current draw while driving is mostly not due to fancy electronics.

Additional top-up charging might sometimes be necessary(or at least useful) because of A) self-discharge and B) standby current caused by standby circuits including but not limited to car alarms, remote control etc. Even then it's only useful when the vehicle sits for weeks. 5-10 watts nominal solar panel would be the smallest size where I would start. If that sound like a lot, nothing is needed. Most problems in normal use will be due to faulty battery and or battery contacts, and will not be remedied through gimmicks such as the smallest available trickle charge solar panel. Some people might even install the panel in a way that it only operates while ignition is on(and does nothing as a result). Quoting 17 volt figures actually makes me wonder if this is exactly what you did.

I'm assuming the panel unit is something like this. http://www.biltema.se/sv/Bil---MC/Bil-tillbehor/Bil-el/12-Volt/Solcellspanel-31630/?artId=31630

Pre-heating by auxiliary heater and driving short distances in very cold weather increases the need for trickle or standby charging. At that point solar panels become useless and regularly plugging in will sometimes be necessary.

As SemiMan said, 17 volts is meaningless. You might want to measure the current and see there is virtually zero current even in sunlight.

If the vehicle was something more oldskool and simple than a new(ish) luxury BMW, a master power switch would be much more useful measure for preserving battery during long term parking than a tiny solar panel.


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