How to calculate a Single Light System
1. Add up the hours that the light will be on for to get the Total of Energy Consumed.
2. From that you can Calculate everything you need IE: Solar Panel / Battery / Regulator
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My Calculations
1 Zone
1 x LED FLOOD @ 15W
on for (SEE CHART) hours per night
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-Watt/Hour Winter Chart- - Only ever use 12 volt LED light -
1 Zone - 15W on when required daily average use -- 4pm until 10pm - 6 hours x 15 Watts = 90wh
Total usage per night in Winter = 90wh/d
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-Load and Battery -
House Lights Consumption = 90Wh
90 watt-hours divided by 12 volts = 7.5 amphours taken from system in 1 night
Because we can only use half the energy in a lead acid battery without harming the battery,
the minimum battery size is 7.5 amps x 2 = 15 amp hours.
I want my system to be reliable if we have four consecutive days of cloudy weather,
4 days of autonomy x 15 Amps = 60 amp hours for the battery. = 60 + amp hour battery
(Required Battery Bank = 1 x 60 Ah minimum - True Deep Cycle
cost so far = $15 for LED light + $50 Battery = $65
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-Charging Battery from Panel-
This installation is in a location that gets 4 hours of full sun per day.
Check the charts for this depending on the month in the Season.
To recharge the battery for one day of use we need 15 amps in 5 hours = 15 / 5 = 3 Amps every hour from a 12 volt solar panel array.
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-Solar Panel -
Most load calculations include a discount factor for the inefficiency of recharging the battery.
20% is typical. 3 A / 0.8 = 3.75 Amps.
A single 70W solar array that has an Impp (amps maximum power point) of 3.9A would be suitable
Based on (Model - CS6D - 70P / Manufacturer - Canadian Solar Inc.)
cost of PV Array = $80
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-Charge Controller Rating in AMPS-
The 70W solar array has a short circuit amp rating (Isc) of 4.21A 4.21A x 1.25 = 5.3A
use a 5.3A or larger charge controller with this array to charge the battery.
Cheap example - 10A Unit
For best efficiency to charge use an MPPT Type = $30
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- estimated Cost of mentioned Materials - 20 years / $450. = $500./240 months = £2.08 month = .52 per week ....wow
Have seen 100w poly panel on Net for $100 inc delivery
Have seen 60Ah Varta Leisure Battery 12V 60Ah for around $50 inc delivery
20A Charge controller $10 - $30 - mppt prefered of course
1 QUALITY External (For in or out & VERY BRIGHT) LED Light 1 x 15w = $15
100m of .75mm twin and earth from wholesalers = $30
Mounting Bracket for Panel = $20
Estimated Total = $200ish
Also required - Fuse box / switches / bits ..
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-Solar Panel specification-
CS6D - 70P..... manufactured by Canadian Solar
Related power
70W
Open circuit voltage Voc(V)
22.1V
Short-circuit current Isc(A)
4.21A
Optimum operation voltage Vmp(V)
17.8V
Optimum operation current Imp(A)
3.93A
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Hope the above can inspire you.
Not mentioned above are Switches, Inverters, Distribution, Heating, Health & Safety,
etc ... Caution -12V Batteries can Cause Fire if not Fused or Stored Correctly-