BajaNomad

solar question

BigOly - 3-25-2017 at 11:46 AM

A friend gave me a new 100 Watt solar panel. Can I use this to keep a 12 volt deep cycle battery charged for my generator? Maybe I need a "controller"?

Controllers

bajaguy - 3-25-2017 at 11:57 AM

http://www.harborfreight.com/30-amp-solar-charge-controller-...

https://www.amazon.com/dp/B00FB3OPKM?psc=1

willardguy - 3-25-2017 at 12:09 PM

whats the panel voltage?

Russ - 3-25-2017 at 12:25 PM

Yep it should work if it's a 12v panel and you go thru a cheep charger. I remember paying $12 awhile ago for one like this.
https://www.amazon.com/Schumacher-SPC-7A-Solar-Charge-Contro...
I use it for boat, quad, gen and camper batteries. The ones above appear to be a higher quality though and not much more $

BigOly - 3-25-2017 at 12:30 PM

Panel volt says 17.48. Can you tell me the distance I can have between the controller and the battery? I tried to use a distance calculater but it's above my pay grade.

larryC - 3-25-2017 at 06:55 PM

For a 100 watt panel I would use a 10 amp rated controller. Should work just fine. The longer the wire run the less amps will actually get to the battery so keep the run as short as possible. In the real world that 100 watt panel will only give you about 77 watts so a 10 amp controller is a little bit of over kill but better to go a little big than a little small. Morning star makes some good small controllers. I used a really cheap controller in my garage to maintain some batteries but the cheapy controller failed and ruined a couple of batteries which cost me over a $100 to replace so no more cheapies for me.

Alm - 3-26-2017 at 05:48 PM

Quote: Originally posted by BigOly  
Panel volt says 17.48. Can you tell me the distance I can have between the controller and the battery? I tried to use a distance calculater but it's above my pay grade.

This is a nominal 12V panel. Any PWM controller from 7-10A will do. Leaving 20% margin is recommended, so it makes it 10A. Expect to pay $30 or more. Stay away from cheap cr-ap on Amazon or Chi-bay.

I would get another 2 panels like this, and use Grape PWM controller from Home Depot, $40. 300W array with 2*6V batts would keep you afloat on most days, and you would only use generator for high-current loads like microwave. Batteries would be happier too, with generator alone they are never fully charged.

Max distance depends on the wire gauge.

larryC - 3-26-2017 at 06:38 PM

Alm
He only wants to keep a generator battery charged not his house batteries.

Never heard of a grape charge controller, is it new?

willardguy - 3-26-2017 at 06:39 PM

Quote: Originally posted by Alm  
Quote: Originally posted by BigOly  
Panel volt says 17.48. Can you tell me the distance I can have between the controller and the battery? I tried to use a distance calculater but it's above my pay grade.

This is a nominal 12V panel. Any PWM controller from 7-10A will do. Leaving 20% margin is recommended, so it makes it 10A. Expect to pay $30 or more. Stay away from cheap cr-ap on Amazon or Chi-bay.

I would get another 2 panels like this, and use Grape PWM controller from Home Depot, $40. 300W array with 2*6V batts would keep you afloat on most days, and you would only use generator for high-current loads like microwave. Batteries would be happier too, with generator alone they are never fully charged.

Max distance depends on the wire gauge.


what part of this don't you understand? :rolleyes:

solar question


"A friend gave me a new 100 Watt solar panel. Can I use this to keep a 12 volt deep cycle battery charged for my generator? Maybe I need a "controller"? "



Alm - 3-26-2017 at 07:42 PM

Willardguy, from my experience, when somebody asks whether they need a controller with 100W panel, they need more than a simple "yes". The questions following the initial question confirm that they do.

Larry - yes, it's new. 40A PWM with Bluetooth monitoring, Tcomp and adjustable setpoints. Better bang for the buck than Morningstar.


[Edited on 3-27-2017 by Alm]

willardguy - 3-26-2017 at 08:02 PM

Quote: Originally posted by Alm  
Willardguy, from my experience, when somebody asks whether they need a controller with 100W panel, they need more than a simple "yes". The questions following the initial question confirm that they do.

Larry - yes, it's new. 40A PWM with Bluetooth monitoring, Tcomp and adjustable setpoints. Better bang for the buck than Morningstar.


[Edited on 3-27-2017 by Alm]


all he wants to do is maintain a 12 volt generator battery!

Alm - 3-26-2017 at 08:10 PM

Quote: Originally posted by willardguy  

all he wants to do is maintain a 12 volt generator battery!

He wants to maintain it with solar. And it appears that he doesn't know how. Wouldn't have asked questions here if he did, would he?

[Edited on 3-27-2017 by Alm]

willardguy - 3-26-2017 at 08:14 PM

Quote: Originally posted by Alm  
Quote: Originally posted by willardguy  

all he wants to do is maintain a 12 volt generator battery!

He wants to maintain it with solar. And it appears that he doesn't know how. Wouldn't have asked questions here if he did, would he?

[Edited on 3-27-2017 by Alm]


:wow:

SteveWil - 3-27-2017 at 09:25 AM

Get the cheap controller and you can use 14 gauge wire for 200 feet (400 foot round trip), I would use 12 gauge for longer run. mount the controller close to the battery ( 10 feet or less). This is for just maintaining a battery and not trying to get the most out of the systems.

Alm - 3-27-2017 at 10:57 AM

Get cheap controller and treat your battery as disposable, or get a better controller and keep your battery for years. Your choice.

Do your math. Using 14 gauge wire 200ft one-way distance, a 100W panel will work as 15W - which might be enough, give small battery size. Or it might be not. The objective of maintenance is keeping voltages where they should be. If the weather and self-discharge require min 50W panel, then you need min 50.

IMO, the best place to ask questions about small solar is rv.net. Not here.

[Edited on 3-27-2017 by Alm]

SteveWil - 3-27-2017 at 12:11 PM

I disagree about the cheap controller, in THIS situation it will do the job just as well as a high priced controller.
Your math is good but, all he needs in this situation is a 15W changing system, to maintain the starting battery. We may be thinking of maintaining the battery differently. I am thinking the solar will only be used to keep the battery at a float stage, when the generator is started the generator will replace the power used to start the generator. So very little power will ever be needed from the solar panel.

Alm - 3-27-2017 at 02:30 PM

With cheap controller the chances of failure are too high. Besides, they often have Float fixed at the wrong value and no temperature compensation. By cheap I mean anything unknown and under $30-35 per 10A unit. Batteries cost more than that, plus inconvenience.

Morningstar 10 @$50 is good enough. Grape 40 is nicer and cheaper, though it's new (a year?), short track record. I recall some $30-ish models at Amazon with relatively positive reports but I wouldn't trust those as much as MS or Grape. $50 units can fail too, but the lower you go, the less you'll be getting.

Speaking of maintenance... Generator, when run only occasionally and for a short time (otherwise they do indeed need more solar), will not bring battery back to 99.9% full. This is the job for maintenance charger and it should be powerful enough to bring it up to 14.x once a day, and then keep it at Float. It's better to have more power than not enough.

del mar - 3-27-2017 at 02:54 PM

:lol:...best to just let it go steve.......

SteveWil - 3-27-2017 at 04:39 PM

Quote: Originally posted by del mar  
:lol:...best to just let it go steve.......


Running low on popcorn? :saint:

:tumble:

$50 is cheap

Bajavanadu - 3-28-2017 at 08:02 AM

I have a 50 watt panel charging my deep cycle with a cheapo 10 amp controller, it puts out 2-3 amps per hour in good sun. A 10 amp controller will be just fine for your panel. Amazon.com has them for 15-20 bucks.

Alm - 3-29-2017 at 10:35 AM

One thing you should understand, Steve - people here have nothing else to do. Most threads deteriorate after the first 3-4 posts, this one has been holding up way too long already :)