How to Calculate Solar Panel & Battery
How to Calculate Solar Panel & Battery
(OP)
Hi Gurus,
I plan to power Three 30W LED Lights with Solar Panel for 10 hrs at most per night. Least average sunlight hours at location is 3 hrs (in Dec). This is my first Solar project and I would like to confirm if my Solar Panel and Battery selection calculations are fine:
Total Load : 3 x 30W = 90W
Watt Hour : 90W x 10hrs = 900 WHr
Required Solar Power output (in Dec) = 900 WHr/ 3Hr = 300W
Hence, I would need a 300W 24V solar Panel to power THREE 30W LED lights during low sunlight periods.
12V Battery Bank:
90W/12v = 7.5A x 10Hrs = 75AHr
I shall choose 100AHr c/20 Deep cycle Battery.
I would appreciate your feedback. Thanks
I plan to power Three 30W LED Lights with Solar Panel for 10 hrs at most per night. Least average sunlight hours at location is 3 hrs (in Dec). This is my first Solar project and I would like to confirm if my Solar Panel and Battery selection calculations are fine:
Total Load : 3 x 30W = 90W
Watt Hour : 90W x 10hrs = 900 WHr
Required Solar Power output (in Dec) = 900 WHr/ 3Hr = 300W
Hence, I would need a 300W 24V solar Panel to power THREE 30W LED lights during low sunlight periods.
12V Battery Bank:
90W/12v = 7.5A x 10Hrs = 75AHr
I shall choose 100AHr c/20 Deep cycle Battery.
I would appreciate your feedback. Thanks
RE: How to Calculate Solar Panel & Battery
RE: How to Calculate Solar Panel & Battery
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RE: How to Calculate Solar Panel & Battery
RE: How to Calculate Solar Panel & Battery
RE: How to Calculate Solar Panel & Battery
Keith Cress
kcress - http://www.flaminsystems.com
RE: How to Calculate Solar Panel & Battery
Its to light up a large bill board. 10Hrs is a worst case scenario (during dark winter months). It may not run for 10 Hrs, as I intend to incorporate a controller to turn-off the lights possibly after 3AM.
RE: How to Calculate Solar Panel & Battery
As mentioned above you need to greatly over provision to make this work acceptably. There are many points to hit to prevent expensive failure, immediate or eventual.
To make this work you need to:
1) Size the batteries to run the lights without much solar input for a week.
2) Size the solar to fully charge the batteries in cloudy weather to be 80% more than the solar required in sunny weather.
3) Include a solar charger that will not over-charge the batteries.
4) Include a battery manager that will accurately prevent over-discharging.
5) Use an ambient sensor to turn the lights on ONLY when needed at night.
6) Manage the battery temperatures to temps as required by the chosen battery chemistry.
It would also help if you can prune off any unneeded running time. For instance, do you really need the billboard lit between 3AM and 5AM? Is the billboard in a location that cars of interest could actually trigger it to turn ON lighting as they pass which would additionally make the sign more effective?
Keith Cress
kcress - http://www.flaminsystems.com
RE: How to Calculate Solar Panel & Battery
So with only 3 hours sunlight you're looking at maybe 1 kwh/kw. Which is about what you need.
but then add on the impact of latitude and you're probably down to about 5-600Whr/kW of panel.
So for worst case you probably need about 2kW nominal power rating to power your lights in winter. Your issue then is how do you control and not damage the panels or lights in the summer when you probably have 4-5 times the electrical power you need or maybe even more given the nights are so short.
some covers for the panels you don't need might be a good idea....
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: How to Calculate Solar Panel & Battery
I have done solar and inverter design and installation for more than 10years.
Your design calculation are fairly much in order. You provided a 25% oversize battery during the worst sunlight weather condition.
Corrections you need to make:
1. Choose the same voltage rating for your battery and solar panels. You cannot have a 24W solar panel charging a 12V battery. It will damage the battery. You can of course use two batteries of 12V in series for a 24V solar panel.
2. Your LED lights have to be the same voltage rating as your solar panel and battery(unless you have some converters in between)
3. Be sure you have a very good charge controller to regulate power input from your solar panel, to deliver optimal power output to run those LED lamps and charge the batteries. A bad charge controller will keep supplying unregulated power to the batteries and over charge them, during periods of greater light intensity.
So with 24V battery, load current=90/24=3.75A. Required AH=3.75*10=37.5AH. So you need one 24V Deep cycle Battery of about 50AH, or two deep cycle batteries of 12V each of 50AH.
Good Luck.
Kind Regards
RE: How to Calculate Solar Panel & Battery
In the Winter the sum may be less than 20 degrees above the horizon.
California calculations and estimates for standby reserves may not be valid.
Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
RE: How to Calculate Solar Panel & Battery
Dan - Owner
http://www.Hi-TecDesigns.com
RE: How to Calculate Solar Panel & Battery
Yes, you can practically use a 24V MPPT solar panel to charge a 12V deep cycle battery, but why do that ?
The inherent operating problem is that the solar panel voltage of 24V is pulled down to match the battery voltage of 12V.
This in turn pulls the panel voltage away from its optimum operating voltage , reducing the panel power output and operating efficiency.
Doing this is not best-practice. For cost reasons, I agree with you, especially if you cannot easily get a 12V solar panel of same power rating.
RE: How to Calculate Solar Panel & Battery
Dan - Owner
http://www.Hi-TecDesigns.com
RE: How to Calculate Solar Panel & Battery
I totally agree with you. Was thinking through my tropics lens. For regions with varying sunlight intensity, this indeed is a valid and required consideration. Thanks very much !
RE: How to Calculate Solar Panel & Battery
The OP seems to have left the room anyway, since he doesn't seem engaged in any way.
Keith Cress
kcress - http://www.flaminsystems.com
RE: How to Calculate Solar Panel & Battery