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Author Topic: Charge expectations from a 30w Solar panel  (Read 11162 times)

TacoEvolution

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Charge expectations from a 30w Solar panel
« on: April 27, 2009, 09:40:25 AM »
Hey Everyone

I've just bought my first trailer and I'm trying to decide whether to upgrade to 2 6 volt battery's or get a Solar panel.

I'm looking  at a Sunforce 30w Solar Panel

What can I expect for charging per day?

thanks for the help

Mark

Ned

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Re: Charge expectations from a 30w Solar panel
« Reply #1 on: April 27, 2009, 10:09:23 AM »
A 30W solar panel will give you perhaps 2A at best.  That's about enough to keep the battery charged in storage without any loads.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Luca1369

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Re: Charge expectations from a 30w Solar panel
« Reply #2 on: April 27, 2009, 11:27:59 AM »
Ned's call is right.  If you divide 30 watts by 12 volts (the charging voltage) your panel should ideally put out 2.5 amps, but you'll likely never see that.  Position of the panel to the sun counts for quite a bit. 

FWIW, I've used solar panels for 20 years on my sailboat and had them mounted so that I could pivot them daily to keep them aligned with the sun for maximum output.  I've seen setups where people had their panels mounted with a mechanism that would track the sun to keep the panels aligned, but those were usually huge panel setups where the owners wanted 20+ amps per hour. 

The dimensions of the panels you mention are similar to panels that put out much more amperage, although the price for your panels is quite a bit lower of course.  For the size, I'd upgrade to a more powerful panel and use two 6-volt golf cart batteries (depending of course on your power consumption needs and your budget).

Steve
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TacoEvolution

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Re: Charge expectations from a 30w Solar panel
« Reply #3 on: April 27, 2009, 03:45:23 PM »
After a bunch of humming a hawing I've decided to get the 6 volt upgrade by my calculations it should give me 4 days of power while dry camping.

thanks for the help.

Mark

Ned

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Re: Charge expectations from a 30w Solar panel
« Reply #4 on: April 27, 2009, 04:23:36 PM »
2 6V batteries will give you 220AH total capacity, or about 110AH of usable power.  That's just 27AH per day, a very light load.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Ron

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Re: Charge expectations from a 30w Solar panel
« Reply #5 on: April 27, 2009, 05:12:40 PM »
I would recommend a larger capacity solar panel.
Ron & Sam-home is where we park it. Currently located   HERE

Ned

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Re: Charge expectations from a 30w Solar panel
« Reply #6 on: April 27, 2009, 05:51:22 PM »
If you don't mind, would you post your usage calculations and we can tell better what battery and solar capacity you would need.
-- Ned -- Fulltimer 1997-2013
1997 Holiday Rambler Endeavor LE
2007 GMC Canyon

Greggk

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Re: Charge expectations from a 30w Solar panel
« Reply #7 on: November 08, 2009, 07:14:24 PM »
what is the calculations to figure out what is needed for daily use? then from there how do i figure out what kit i would need?

Gary RV_Wizard

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Re: Charge expectations from a 30w Solar panel
« Reply #8 on: November 09, 2009, 11:18:05 AM »
You need to estimate the DC amp-hours you will drain from the batteries every day. That's interior lights, circuit boards for fridge and water heater, water pump demand, furnace fan if that will be in use, and any inverter usage you may have (tvs, satellite, microwave, etc). Get the amp draw for each item and estimate how many hours per day it is typically used and multiply each to get amp-hours.  Some of it is going to be a SWAG, of course, but you need to come up with some idea of the amount of battery load, then figure the solar capacity that will replace it. Or perhaps just partially replace it and plan on using a generator for an hour or so a day.  This effort also tells you how much battery capacity you need - you need to have about 2x as many amp hours in the battery rating as the amount you will use every day. That's because you should only draw a battery down to about 50% capacity. Any more will shorten its life.

Solar panels are measured in watts, so the basic formula is watts = amps x volts. The panel charges at around 15v,  so divide the wattage rating by 15 to get the amps it can load into the battery. That's only in full sum, so estimate less for off-peak hours when the sun is at a lower angle.
Gary
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geodrake

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Re: Charge expectations from a 30w Solar panel
« Reply #9 on: November 09, 2009, 12:05:06 PM »
Gary; That is about the best explaination of these cals that I have seen, but one question remains for me regarding charging.  If there is a 2 amp charge for one hour, then is that 2 amp hours that is returned?     
George Drake

Greggk

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Re: Charge expectations from a 30w Solar panel
« Reply #10 on: November 09, 2009, 07:59:02 PM »
ok so i don't have a camper yet, more specifically we are looking at a pop-up. say i buy a p-up that sleeps 7. i want to be able to power a tv/dvd player for a few hours, a little dorm room fridge and a furnace over night, and then lights for a few hours each day. what would you recommend? i want to run a generator periodically through the day for the necessities, but stored up solar power for night use, and the rest of the day when generator isn't running...

DonTom

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Re: Charge expectations from a 30w Solar panel
« Reply #11 on: November 09, 2009, 09:24:35 PM »

I'm looking  at a Sunforce 30w Solar Panel

These solar panels which come with a solar controller and other goodies are sometimes on sale for less than $170.00. That's what's on top of my RV, (along with a couple of other small solar panels for a total of 65 watts.)
-Don- SF, CA
-Don-   AA6GA

2000 Fleetwood Tioga 24D, 7.4L

Auburn, CA or Cold Springs Valley, NV or  Reno, NV

jhonebhrestom

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Re: Charge expectations from a 30w Solar panel
« Reply #12 on: April 27, 2010, 07:23:45 AM »
A much smaller system, say capable of giving 360 Watts during peak sunlight only would be a lot cheaper to buy, but the operational expenditure of the entire system would be much greater as a diesel generator is not cheap to run, or you rely on mains back up.

garyhouser

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Re: Charge expectations from a 30w Solar panel
« Reply #13 on: June 11, 2010, 10:51:37 AM »
Get a portable dvd/tv player that is a stand alone, forget the refrigerator and use an ice chest and use a small catalytic heater with much caution and cracked windows. Don't expect to be able to run anything much without several batteries and more solar cells than you are willing to carry around. If you are in an area with lots of wind such as the coast then a wind generator could do more good than solar. I lived on a 48' catamaran with 2 large batteries solar cells and a wind gen and could run interior lights fans and radios without draining the system, but not much more. Look here http://homepower.com/home/  for some good alt energy information.

tvman44

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Re: Charge expectations from a 30w Solar panel
« Reply #14 on: June 11, 2010, 05:02:42 PM »
Make the battery change to 2 6 volt batteries and get a much larger solar panel.  I would not waste my time or money with anything less that 150 watts.

 

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