How much solar power required?

Discussions about solar power and solar energy projects.
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just4havinfun
Posts: 10
Joined: Tue Dec 03, 2013 8:28 am
Location: Bay City, MI

How much solar power required?

Post by just4havinfun » Thu Dec 05, 2013 11:34 am

I am looking for an enclosed trailer to convert into a camper of sorts. My plan is to add a deep cycle battery for lights, radio, and other accessories. How much solar power would be required to adequately charge a 12 volt deep cycle(marine) battery during the daylight hours? I know it would depend on how much the battery is drained each day, so say I used 50% of the battery charge each day.

techman
Site Admin
Posts: 1329
Joined: Thu Dec 22, 2011 11:49 am

Re: How much solar power required?

Post by techman » Thu Dec 05, 2013 8:07 pm

There are other variables involved such as how much power you want to use each day. Use that as your calculation and build your system based on those numbers.

For example, say you want to use about 1000 watts per day total. Lets say 100 watts for 10 hours. Then depending on where you live, consider there is about 5 peak sunlight hours per day.

You need about 200 watts of solar panels to give you 1000 watts in 5 hours. Add more for safety and to cover cloudy days.

The batteries for such a system would be about 83 amp hours, but a battery bank is considered drained at 50% so you need about 160 amp hours of batteries.

Hope this helps some

mr bugsier5
Posts: 63
Joined: Sat Jun 15, 2013 12:36 pm
Location: Brielle , west coast of holland(europe)

Re: How much solar power required?

Post by mr bugsier5 » Thu May 29, 2014 7:16 am

even more battery standby power would be better, the bigger the bank, the lesser the strain you put on it, the longer they live, and the lesser yoy load them the better it is for a lead acid battery, i always say , you cant have a to big battery bank.

and also inportant is that the bigger the instalation connected to it , the more advisable it is tu use bigger battery bank voltages .

not only smaller wires , but also mutch less strain on the bank. ;)
dont be afraid to ask!, a stupid question does not exist!
forgive me my bad English!, as long as you know what i mean it,s fine for me!
(you thry dutch, wont be easy to! HA HA!)

mr bugsier5
Posts: 63
Joined: Sat Jun 15, 2013 12:36 pm
Location: Brielle , west coast of holland(europe)

Re: How much solar power required?

Post by mr bugsier5 » Thu May 29, 2014 7:27 am

the instalation i use on my offgrid tugboat here in the netherlands is 24 volts at 460 amps,
only have a smal solar system on the roof off the wheelhouse with two panels of 140 wats in series, delivering 45 volts at 8 amps to my mppt controller , max charge amps y have seen is around 15 amps at 24 volts.(my controller is max 15 amps, i'm experementing with differend makes and types of chargers)
i power a compressor fridge via a inverter at 230 volts ac , a tv, gsm charger and other misilainius (i can also use a washing machine on it, but when y use that i will mostly start my 7kva 230v diesel generator, letting it charge my battery bank the same time via the inverter /charger (50 amps), to top up the battery bank.
also when y use bigger loads i often start that generator, not to stress my bank to mutch, used yhis system for over 18 years, average battery bank life is 10 to 12 years, using quality semy traction batterys, connected serie/parralel.

works fine for me! :mrgreen:
dont be afraid to ask!, a stupid question does not exist!
forgive me my bad English!, as long as you know what i mean it,s fine for me!
(you thry dutch, wont be easy to! HA HA!)

techman
Site Admin
Posts: 1329
Joined: Thu Dec 22, 2011 11:49 am

Re: How much solar power required?

Post by techman » Wed Jun 04, 2014 8:53 am

Mr bugsier, your system sounds pretty good. The mppt controller makes a huge difference. One day I would love to make it out there and see your boat. Its a dream I always had to live on a boat.

techman1219
Posts: 3
Joined: Fri Jul 04, 2014 3:20 pm
Location: Nashville, TN

Re: How much solar power required?

Post by techman1219 » Fri Jul 04, 2014 3:44 pm

Hello all. This is HBW from Youtube. This is really all mathematical. Let me insert the equations below:

Angle of the panels:
Angle = latitude*0.76+3.1

Array sizing:

Use http://www.sunrisesunset.com" onclick="window.open(this.href);return false; to determine the worse of the worse.
Worse day in Jan/Feb and compute total hours of sun / 2 = Worse case sun hours
Worse case sun hours 4.875

(Total Power Requirements in kW * 1000 / Worse case sun hours) * 2 = Array size

(4kwh * 1000 / 4.875) * 2 = 1641w

Reserve Power Battery Calculation:

((Total Power Requirements * 1000 x reserve days) / battery voltage) * 2 (because we never want to go lower than 50% discharge)

((4kwh * 1000 * 5) / 24V) * 2 = 1666.7
((4kwh * 1000 * 5) / 48V) * 2 = 833.3

To compute the number of batteries:

(Reserve Power Battery / Battery reserve cap) * the number of batteries to make the voltage

(1666.7 / 210rc) * 2 (24v using 2 12v) = 16
(833.3 / 210rc) * 4 (48v using 4 12v) = 16

It's going to be 16 either way and heavier copper cable is expensive and the component cost is the same; so 48v configuration.

If there is any questions I'll be around.

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