Will a 50 Watt solar panel have enough power?

lightseeker2009

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If I use a max of 300 watts of power in a single night, once a week, will a 50 watt solar panel be able to fully recharge the deep cycle battery in the rest of the week?
Lets say there is average to good sunlight available per day.

Thanks Guys
 

TinderBox (UK)

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As long as you get reasonably reliable sun and you get solar power 25watt for 14hrs you should have 300watts of power stored, so over a week as long as you get 3hrs of sun a day for 6 days you should be fine, I always estimate solar panels as 50% of these quoted wattage so 50w is 25w if you are wondering, I am not the best at maths so hopefully others will confirm this.

John.
 
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Lynx_Arc

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It depends on the voltage of the panel and your storage voltage too. If you are charging batteries directly with the panel then if you use 300 watts from your battery theoretically it should take 6 hours of full sun to charge the batteries back up if there were no losses. There will be losses but even at half output 12 hours of sun per week shouldn't be a problem unless your climate has you cloudy 6 days a week 2-3 days should easily cover it all.

Now if you are using 300 watts for a WHOLE day with 6 days to recharge it then you need to figure watt-hours and calculate accordingly I would figure on needing 2 times a much charging time per watt-hour to recharge your batteries that would allow you losses and weather issues that could last a day or two.
 
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RobertMM

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Some use a rule of thumb of 2:1, that is 2 watts for every Ah of battery.
I followed that and put up a 200watt panel powering a 100Ah AGM deepcycle battery, with 600watt inverter.

I never get low on power even on cloudy days.
 

lightseeker2009

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Does he not mean 3 hours of 100 watts, or, 6 of 50 watts totalling in 300 watts for the whole night, at least that's what it though the op meant.

John

100% correctly understood:)
300Watt max per night, just once a week.

Just want to ask something relevant.
As solar panels cannot charge during the night, the battery will not be charged in one go, but intermittently over a couple of days.
That is not a problem right? How much life expectancy might be lost by using solar panels to charge a battery over a couple of days, versus a 6 amp charger who does it in one session?
 

TinderBox (UK)

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As long as your solar panel has a reverse charging diode protection, It should already have one.

Slow charging is good for deep cycle battery`s according to the faq below.

Unless you already have one a ac/dc clamp meter would be a great buy it has an good DMM (multimeter built in with test leads) (there is a good cheap dedicated dmm if you need one?), this one has an 1ma dc accuracy on the 2amp scale so you can check charging current and also check for parasitic drain without breaking the circuit (you have to be able to separate the wires to measure or the interfere with each other), and it`s a great price "UNI-T UT210E" check youtube for video reviews.

https://www.youtube.com/watch?v=9azDW7NSCjo

http://marine-electronics.net/techarticle/battery_faq/b_faq.htm

John

100% correctly understood:)
300Watt max per night, just once a week.

Just want to ask something relevant.
As solar panels cannot charge during the night, the battery will not be charged in one go, but intermittently over a couple of days.
That is not a problem right? How much life expectancy might be lost by using solar panels to charge a battery over a couple of days, versus a 6 amp charger who does it in one session?
 
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DarlingSoul

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[FONT=q_serif]Will presuppose, 6 h full sunlight, and a top notch MPPT modulator, no trickle charge, and total 80% efficiency.
50W (STC labeled, not the real world power) usually has Vmp=17V, Imp=2.9A[/FONT]

[FONT=q_serif]Case 1. Li-Ion battery Turnigy Graphene Professional 3000mAh 3S 15C LiPo
This tipe of battery suports max 5C but we have max cca 4A available so will be 1C[/FONT]

[FONT=q_serif]It will take 50–60 min to fully charge one Li-Ion battery Turnigy Graphene Professional 3000mAh and 6 packs / day[/FONT]
[FONT=q_serif]Case 2. 12V 75Ah Lead Acid battery[/FONT]
[FONT=q_serif]With 24Ah from the solar panel per day we can charge in 6 hours from 68% to 99.9% one 75Ah 12V Lead Acid battery.[/FONT]
[FONT=q_serif]Case 3. 5V 10000mAh Power Bank[/FONT]
[FONT=q_serif]This require usually 10–16W for charging depending on the brand and takes cca 3 hours. So in 6 hours you can charge roughly 2x3 pcs Power banks.[/FONT]
[FONT=q_serif]We would like to hear what were your results if you decide based on these options.
https://www.quora.com/With-50-watt-...ty-battery-can-be-full-charged-on-a-sunny-day
Best solar shed light[/FONT]
 
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iamlucky13

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100% correctly understood:)
300Watt max per night, just once a week.

Just want to ask something relevant.
As solar panels cannot charge during the night, the battery will not be charged in one go, but intermittently over a couple of days.
That is not a problem right? How much life expectancy might be lost by using solar panels to charge a battery over a couple of days, versus a 6 amp charger who does it in one session?

Watts are a unit of power, not energy. If you use 300 Watts for one hour (or 60 Watts for 5 hours, etc), you've used 300 Watt-hours of energy.

If Watt-hours is what you're actually talking about, 50 Watts is fine for once a week, and in really good conditions might even just barely suffice for daily. For a 300 Watt-hour per cycle use level, I'd recommend at least a 50 Amp-hour battery.

Definitely use a charge controller to avoid overcharging the battery. You shouldn't need to spend the extra on a MPPT type for a weekly use of 300 Watt-hours on a 50W panel.

Charging over multiple days is not a major problem. Just don't leave the battery at a low state of charge for weeks at a time and the life reduction should be pretty small.

Tinderbox mentioned a reverse discharge protection diode. Most panels that I've seen actually don't have one, but the charge controller should.
 

Arizona_Mike

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If I use a max of 300 watts of power in a single night, once a week, will a 50 watt solar panel be able to fully recharge the deep cycle battery in the rest of the week?
Lets say there is average to good sunlight available per day.

Thanks Guys

I assume you mean you use 300 watt hours. I'm going to take it for granted that you have a battery that can provide this within it's optimum operation condition (stay above 40% charge for a lead-acid for example).

If the panel has an honest rating it will tell you what you can expect mid-day. A stationary panel at the right angle will give you a multiple of it's rating in watt hours per day on an average day. That multiplier can be found on insolation maps
world_solar_insolation_data.gif


Some maps are annual averages and some are seasonal averages. Assume 2-4x per day and 85% charge efficiency.
50x0.85x(2--4)= 85-170 WHr. You should recharge in 2-2.5 days under those conditions.'

Mike
 

StorminMatt

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world_solar_insolation_data.gif


Some maps are annual averages and some are seasonal averages.

And this distinction between annual and seasonal averages is VERY significant. For instance, if you take a look at Northern California on this annual average map, insolation is nothing too special compared to other parts of the world. However, if we look at summer insolation ONLY, Northern California would be one of the top spots (if not THE top spot) in the world. However, our gloomy, rainy winters tend make our annual averages seem rather mediocre. But knowing the difference can make a HUGE difference when it comes to the feasibility of solar power for various uses. For instance, our constant summer sun makes solar power GREAT for powering air conditioners or summer cabins. But solar power in winter? Not so much.
 

TinderBox (UK)

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Beware of fake wattage claims on fold-up portable solar panels, I have an 24watt version, But the convertor only puts out a maximum of 3amp at 5volts using ohms law that is only 15watts.

Though the extra 9watts will help with low light situation giving the convertor a little extra help.

John.
 
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IonicBond

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Lets see - 50w / 18v (nominal panel voltage) = 2.77A maximum capable under the best of conditions. Your charge controller will limit the CV voltage of course, but this is what the panel is capable of.

That would be similar to putting a "maintenance" charger on your 100ah agm. It is not recommended to use maintanance chargers for moderate to deep discharges - only top up's.

EFFICIENCY is the rule here. For an agm, strive for a minimum of .05C (100ah * .05C = 5A minimum for *efficiency*) regardless of how many days of solar you have to charge it. Standard agm's can accept up to .25C maximum charge without buckling /warping plates in the process. So, about 25A charge current maximum.

With solar, mere visible dusk-to-dawn daylight doesn't count. Typically the most efficient hours center around noon. Depending on where you are, that could only be a few hours. Consult what is known as "solar insolation charts" for your area to see what hours are truly considered useful, aside from early morning and late afternoon weak exposure. Those primary noon-centered hours, along with the amperage / wattage of your charge setup, compared to your discharge level, will let you determine how many day(s) it will take to fully charge.
 
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Str8stroke

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I didn't have time to read all the above posts, but if nobody mentioned Solar Controllers, make sure you get the most efficient you can find.

Check out the MPPT type controller. I also suggest solid copper connections, heavy awg high quality wire/cable. Seal all outdoor connections from the elements, I also use lots of dielectric grease (aka basically Nyogel). Keep your panels clean. Just a small amount of dust can make a difference. I clean mine weekly with Rain X window cleaner. Then make sure you have them placed in the proper location, angled properly for max sun.

Good luck.
 
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