How many watts is your Solar setup?

[Trekking]

Looking around at panels and wondering if 240 watts or 480 watts wound be better for a van setup.

 

[Reducto]

I have 235 watts and it is able to run my small dometic fridge and laptop all day, most days. I do need to run my generator about once a week in winter or when it's cloudy.

240 is good for most people but it really depends on what you want to run with it, how often you have many cloudy days in a row, and how tolerant you are to running out of power every now and then. More is always better if you can afford the cost and roof space.

 

[GotSmart]

How much are you willing to spend, and how much room do you have for battery storage?

Batteries weigh about 65 lbs each. For a 240V set up you would need 4. $40 each for reconditioned, and $120 each for new. You need a place for them that is outside your breathing space.

Kits get expensive. Perhaps $800 for a nice 240V.

Another $100 for wires and various parts.

http://www.solar-electric.com/rvandsmbasoc.html

These people will give you great advice. They are the place Bob recommends, and where I am going for my set up. Solar is their life! Their quality is the best, and they will work with your budget.

 

[Lucky mike]

I run 3 240's but Im in an RV.... with 6 batteries at the moment...

 

[crazybill]

I have 120 watts and it's enough for my very basic needs. 2 6 volt golf cart type batteries.
No fridge, but I run a ham radio at times. Also a laptop, but not a lot.
I got the panels for free from a friend who was upgrading his setup, which is how I settled on the wattage.
-Bill-

 

[Willy]

I lent out my 68W panel to a buddy, for the summer, and am getting by with 120W. With 3 storage batteries, 1 dedicated to the cooler (which is set at around -2 deg/C). It provides PLENTY of power, in the summer, and somewhat more than I need.

For the winter, 190W is sufficient, since I have my cooler in the cab and let nature work for me. Still keep it in the cab during the summer (windows open and radiant barrier on the windshield when parked), since power isn't an issue. ..Willy.

 

[SternWake]

198 watts. More than enough in Summer, not quite enough in winter.

This wattage does not meet the battery manufacturer recommended bulk charging currents though. My flooded battery wants 10% of the 20 hour A/H rate. 13 amps. I can just make that in summertime, but the fridge and fans are still drawing a portion of that 13 amps

Too little solar might be able to replenish the amount used, but not meeting the minimum bulk currents will shorten battery life too.

Those with a lot of battery capacity and Not that much solar, should somewhat regularly, have a method to give the batteries a fast charging rate at 20% or higher of the total battery capacity.

So with Solar, more is better, and if you can afford 460 watts, and fit it on your roof, well, your batteries will simply last longer, even if a good portion of that wattage is wasted later in the day.

A temperature compensated hydrometer will tell you how well your solar is treating your batteries. I bet my charging amps vs battery capacity ratio is higher than most, yet after a week, My SG readings are only in the fair(1.250 range), and I have to crank up my charging voltages upto 16v for 90 minutes minimum to get the SG upto the maximum 1.280 baseline.

Without doing this the battery voltage sags more and more each night under the same loading, capacity used, and at the 3 week mark the battery will read 1.220 and perform badly overnight.

This is when the solar is doing 14.8v absorption and then holding 15v float for several hours afterward, each day.

Granted this is a peculiar battery, but it proves the blinking green light, means little.

A solar controller that allows one to change charging voltages is wise.

A total solar wattage which meets a minumum 5% of the 20 hour rate, is wise.

And A wattage able to bring the flooded battery to 16v is wise.

Do not leave devices/ appliances hooked to a battery being charged at 16v

For reference, After my Solar holds my group 31 USbattery Deep cycle battery at 14.8v for 2 hours, then 15v for 3 hours, to get it to 16V, takes 6 amps, and at least 90 minutes to get the SG back to 1.280, and that is weekly.

If I do not treat the battery to a weekly 16V equalization it performs abysmally.
Not all batteries will do this of course, but it appears the bigger the 12v battery, the higher voltages it needs to get the Sg back to baseline.

6v GC batteries require much less baby sitting to get the SG back upto baseline, and getting the SG back upto baseline is the goal, for ultimate battery performance and longevity, if one cares about such a thing.

After all batteries are only rented.

 

[freenez2]

Am in a Ford van:
One roof mounted 245 watt Kyocera panel.
Two 224ah six volt Sun Extender AGM batteries.
Morningstar TriStar 45 Amp MPPT Solar Charge Controller.
Breakers, wire, etc.

I more or less matched the max output of the panel with the ah rating of the batteries. I run a Whynter refrigerator, T.V., lights, laptop, Ipad, cell phone, radio, etc from the batteries. Works great and improved my quality of life a lot.

 

[Trekking]

I can get a great deal from a buddy that owns and installs large solar systems and he has a few skids of 240 watt new panel for $150 each pannel and they have the box and wires mounted may look at just buying 1KW worth of them.

 

[Lucky mike]

thats a good deal!.......pick up a good controller and your set to go!

 

[Mac J]

There is really no point in buying more solar power than one needs even if it is at a good price.
This site can steer anyone in the right direction as to how much solar one needs.

http://gpelectric.com/go-power-calculator

there is a short video to be used as a guide.
this site is provided by the distributer of Go Power. They do not sell retail. The end result will be suitable for ANY brand of solar service. I found the site informative and useful.

 

[Lucky mike]

I think your absolutely right.......some people think that if you have 800 watts on the roof that you have 800 watts coming inside.....more like 80 if you follow the 10% rule ......I personally like the 240 watt panel with 2 batteries with about a 750 watt(peak 1k) inverter.(panels can be added later)...if you cant last a few days on that you have issues......

 

[freenez2]

Experience with the solar setup in my aforementioned post was that power output from the 245 watt panel only reached max output one time. As the batteries have never dropped below 80% the MPPT controller rarely allows much more than a 100 watts max to the batteries. On sunny days the system is floating after a few hours of morning light. The only advantage to having more solar power output is when there are many consecutive cloudy days or if electrical demand is beyond what the batteries are meant to supply. Understanding ones electrical needs in the present and future and building the system accordingly is the way to go.

 

[Mac J]

freenez2

I would imagine that your fridge and your laptop use the bulk of your amp hours. It would be interesting to see if the
Go Power calculator I list is "on the money" as far as your solar needs are.

 

[SternWake]

The only advantage to having more solar power output is when there are many consecutive cloudy days or if electrical demand is beyond what the batteries are meant to supply. Understanding ones electrical needs in the present and future and building the system accordingly is the way to go.

Meeting the minimum bulk charging currents of the battery manufacturer is a big advantage, in terms of battery life and performance.

Often this minimum bulk current, which the batteries only accept when under 80% charged, if very difficult to fulfill via solar.

If one's system never discharges below 80% then perhaps one has too much battery capacity.

If one wants extra capacity, just to have for those cloudy days, then one should have enough solar to properly feed that extra capacity too.

This is if the main recharging system is Solar, if other charging sources are regularly applied until 95% SOC is reached, then the Solar to battery capacity ratio can vary more widely, but if one is primarily recharging by solar, then one needs to better match the solar wattage for the battery capacity.

Otherwise the solar needs to be looked at as negating the electricity used, but not as a charging source that will properly keep the batteries the healthiest.

Having enough solar so that the controller goes into float before noon, even well before noon is not a waste. Having that wattage buffer in the second half of the day is a big advantage, and one can do things like cranking up the fridge, charging all laptops and accessories to better use the excess.

Then when it gets cloudy the system might still have enough gusto to get the batteries up near 100%

 

[freenez2]

Mac J

I looked at the chart and started doing the arithmetic, but found computing actual consumption by the refrigerator difficult. Knowing the actual runtime when considering variations of temperature in the van is guess work. I'd have to log it over a period of days to put in accurate numbers. As the system is already built I don't see the point...
Something else people may want to consider is cost per watt for the modules and whether getting a larger one that doesn't cost much more would be a good way to go. There's a chart in the link below that shows price per watt in the lower in the page.

http://www.solar-electric.com/hiposopa.html

I suppose the same consideration could be given to batteries though I've not done that research.

 

[akrvbob]

I'm not a fan of the usage calculators. They are assuming your batteries and panels are working like new, and they rarely are. They are also using a mythical "average" amount of light.

You get a few days of rain in December or one or two weeks in the summer your marginal system is done, you're out of power. But you keep using it and you abuse your batteries, shortening their life. But if you can afford it, and you get too much solar, what bad thing happens? Your batteries never run down and last a very long time! Sign me up!
Bob

 

[Mac J]

akrvbob, what you're saying may be true but calculators are a good start. Like all measuring devises there is room for error and variables. If it rains, and there's no sun, go for a drive and charge off the tow vehicle.
It's that affording thing that seems more of a draw back to many. Lets face it, if the solar panels and batteries were free we would all dance in the lights. When that happens, sign me up!

 

[TucsonAZ]

I have 1,380 with a 6,000 watt battery bank. You really can't have too many panels, even a slight amount of shade impacts the output greatly, shade in the winter, even worse, cloudy day, two of them in a row, you get my point. I see it like collecting water, I don't want to hope I have enough and end up dying dirty and thirsty, I want to put out a huge tarp so even in the lightest of drizzles I still have enough to get by. I sized for the worst case with a smaller battery bank that I know will get refilled each day.

 

[TucsonAZ]

Batteries are made differently for different things, CCA doesn't tell you much, normally it's an automotive type battery, more plates inside but thinner so they have more surface area, thus they're lighter, they're designed to give a lot of power for a short time.

Marine are only slightly better but far from ideal and I would also avoid those for a solar setup.

The reason I said 6,000w is it's a more universal number, my bank is 24v @ 250 amp hours so 24*250=6,000 but I could have achieved the same thing with the same four 125ah batteries with a 48v/125ah bank or a 12v/500ah battery bank.