Charging a car battery via a solar panel

[ChrisGarrett]

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

 

[Sub_Umbra]

...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.

 

[ChrisGarrett]

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

 

[SemiMan]

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[Rexlion]

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!

 

[lightseeker2009]

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?

 

[Norm]

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

 

[Knight_Light]

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.

 

[SemiMan]

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[Poppy]

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.

 

[lightseeker2009]

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

 

[ChrisGarrett]

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

 

[SemiMan]

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[ChrisGarrett]

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

 

[Knight_Light]

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.

 

[SemiMan]

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[eco007]

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]

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.

 

[lightseeker2009]

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.

 

[ChrisGarrett]

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