SIZING OF PV STANDALONE SYSTEMS2-1

1. SIZING OF PV STANDALONE SYSTEMS:
Daily energy balance approach
Engineer T. Hove
tawandahv2@gmail.com

2. WHAT IS A STANDALONE PV SYSTEM?
• A Stand Alone PV System is made up of a number of individual
photovoltaic modules (or panels).
• These PV modules are then combined into a single array to give the desired
power output.
• A simple stand alone PV system is an autonomous solar system that
produces electrical power to charge banks of batteries during the day for
use at night when the suns energy is unavailable.
• A stand alone small scale PV system employs rechargeable batteries to
store the electrical energy supplied by a PV panels or array.
• Stand alone PV systems are ideal for remote rural areas and applications
where other power sources are either impractical or are unavailable to
provide power for lighting, appliances and other uses.
• In these cases, it is more cost effective to install a single stand alone PV
system than pay the costs of having the local electricity company extend
their power lines and cables directly to the home.

3. TYPICAL PV STANDALONE SYSTEM CONFIGURATION

4. SYSTEM COMPONENTS AND FUNCTIONS
• PV Array: Photovoltaic (PV) solar panels are normally silicon crystal layers that convert sunlight to DC
electricity.
• Batteries – Batteries are an important element in any stand alone PV system but can be optional
depending upon the design. Batteries are used to store the solar-produced electricity for night time or
emergency use during the day. Depending upon the solar array configuration, battery banks can be of
12V, 24V or 48V and many hundreds of amperes in total.
• DC/DC converter: DC/DC conversion allows keeping the voltage on the PV and voltage on the load
separately controlled. There two main types of DC/DC converters depending on the direction of
voltage change: (1) boost converters transform smaller voltage to higher voltage and (2) buck
converters transform higher voltage to lower voltage.
• Charge Controller: A charge controller or charge regulator is basically a voltage and/or current
regulator to keep batteries from overcharging. It regulates the voltage and current coming from the
solar panels going to the battery. Most "12 volt" panels put out about 16 to 20 volts, so if there is no
regulation the batteries will be damaged from overcharging. Most batteries need around 14 to 14.5
volts to get fully charged. The charge controller also prevents the battery from over-discharging. It
monitors the battery voltage and when it is minimum, cuts off the supply to the load switch to remove
the load connection.
• DC/AC Inverter: This is the device that takes the DC power from the PV array or battery and converts it
into standard AC power used by the house appliances.
• Wiring – The final component required in and PV solar system is the electrical wiring. The cables need
to be correctly rated for the voltage and power requirements. The longer the transmission distance,
the thicker are the wires required to limit the power losses to a specified threshold

5. PV STANDALONE SYSTEM SIZING
• The PV standalone system operates off grid, and should
therefore supply the total load autonomously (100 %
reliability)
• The sizing objective of any type of standalone PV system is a
critical balance between daily energy supply and demand
• The PV array must be large enough to supply enough energy
to meet the load demand plus any system losses under the
worst case conditions
• Consequently the efficiency of system components and
electrical loads is of critical importance

6. BASIC STEPS OF SIZING THE PV STANDALONE SYSTEM
• Standalone PV systems are sized to meet specific load
requirements, and involve the following key steps:
Determine the average daily load requirements for each month
Conduct a critical design analysis to determine the month with
lowest solar insolation to load ratio
Size battery bank for voltage and required energy storage
capacity
Size PV array to meet average load requirements during month
with lowest insolation to load ratio
Size balance of system: inverter, charge controller and wiring

8. SYSTEM LOADS
• Properly calculating load consumption is a critical step in properly sizing an
off-grid power system.
• As most off-grid systems are dependent on batteries to store energy, and
these battery capacities are sized based on amp hours, the load needs to
be calculated in amp hours in order to properly size the system
• All loads can be defined as the following:
continuous or non-continuous
at system voltage or at non-system voltage.
• Continuous is defined as 24 hours a day, 7 days a week. Non-continuous,
also referred to as intermittent, defines a load that operates for a portion
of a day, or has different consumption at different times of the day.
• Typical non-continuous loads are lighting, radios on transmit, valves or
actuators, pumps or motors, gate openers, etc.

9. LOAD CALCULATION GUIDELINES
• If the load cannot operate within the voltage tolerance of the system, then power conditioning equipment
will be required.
• Typical power conditioning equipment would be a DC to AC inverter for AC loads, or a DC to DC converter
for DC loads.
• Power conditioning equipment contains losses that need to be included in the load calculation. Typical
efficiencies are 85-95% for inverters and 80-90% for converters.
• Loads can be expressed in any of the formats listed below:
current (amps[A])
power (watts[W], kilowatts[kW])
energy (amp hours[Ah], watthours[Wh], or kilowatthours[kWh]).
• Notice, most utility bills are based on kWh, so this is a common unit for AC loads. Regardless of how the
load is expressed, it will need to be converted to Ah for system sizing calculations.
• Recall from the power equations [Power(W) = Current(A)*Voltage(V)] we can convert from Watts to Amps
by dividing power by nominal voltage [Power(W)/Voltage(V) = Current(A)].
• Some load calculations will be simpler than others depending on the type of load and application.
• Ultimately, all answers will be expressed in the total amount of Amp-Hours consumed over a full day (24-
hour period), for a given nominal voltage (Ah at 12V vs Ah at 24V are different things).

10. LOAD CALCULATION EXAMPLES
• Let’s begin with the simplest example:
• The simplest load is one that is:
expressed in amps and
is continuous and
will operate within system voltage.
• To calculate the load in this example you simply multiply the amps by 24 hours (the number of
hours in a day) to get the daily load in Amp-Hours, often abbreviated “Ah”.
• Example 1:
• 0.5A, 12VDC nominal, continuous load
• 0.5A x 24h/day = 12Ah/day @ 12VDC
• If that same load were expressed in watts instead of amps, we would just convert it to amps by
dividing power(W) by nominal voltage (V) and follow the same procedure.
• Example 2:
• 6W, 12VDC nominal continuous load
• 6W/12VDC = 0.5A x 24h/day = 12Ah/day @ 12VDC

11. LOAD CALCULATION EXAMPLES..continued
• If the load is non-continuous, we simply multiply it by the number of hours per
day it is active rather than by 24.
• Example 3:
• 8W, 12VDC LED light that operates only at night.
• Let’s assume worse case the light will operate for 16 hours in the winter.
• 8W/12VDC = 0.67A x 16h/day = 10.67Ah/day @12VDC
Example 4:
A 12VDC radio that is 1A in standby and 10A in transmit. The radio transmits for 1
hour per day.
10A x 1h/day + 1A x 23h/day = 10Ah/day + 23Ah/day = 33Ah/day @12VDC

12. LOAD CALCULATION EXAMPLES..continued
• Example 5:
A 10A, 24VDC valve that operates for 15 minutes a day and a 20W, 24VDC continuous
controller.
10A x 0.25h/day + 20W/24VDC x 24h/day = 2.5Ah/day + 20Ah/day = 22.5Ah/day @ 24VDC
• If the load is at voltage other than the system voltage then the losses of the conversion
equipment need to be included in the calculations.
• Example 6:
8W, 120VAC LED light that operates only at night.
• Let’s assume worse case the light will operate for 16 hours in the winter.
• Let’s also assume a system voltage of 12VDC and a power conversion efficiency of 90%.
• 8W/90%/12VDC = 0.74A x 16h/day = 11.85Ah/day @ 12VDC

13. LOAD CALCULATION EXAMPLES..continued
Example 7:
5W, 24VDC continuous sensors with a voltage tolerance of +/-10%.
As the load has a small voltage tolerance, a DC/DC converter will be required. 24V +/-2.4V range is much narrower than the battery
range (21.6V to 28.8V) of a nominal 24V battery.
Let’s assume the converter efficiency is 80% and the system voltage will be 24VDC.
5W/80%/24VDC = 0.26A x 24h/day = 6.25Ah/day @ 24VDC
If there are multiple loads, they can be calculated separately and then summed together to get the total load.
Example 8:
Telecommunications tower with a 500W, 48VDC continuous communication load and 50W 24VDC nighttime obstruction lighting load.
Again, let’s assume the worst case for the lighting load is 16 hours in the winter. We’ll also assume a DC:DC Converter will be required
for the 24VDC load, with an efficiency of 85%.
Load1
500W/48VDC x 24h/day = 250Ah/day
Load2
50W/85%/24 VDC x 16h/day = 19.6Ah/day
Total Load = 250Ah/day + 19.6Ah/day = 269.6Ah/day @ 48VDC

14. LOAD SIZING
List all of the electrical appliances to be powered by the PV system.
• Separate AC & DC devices and enter them in the appropriate table.
• Record the operating wattage* of each item.
• Specify the number of hours per day each item will be used.
• Multiply the first 3 columns to determine watt-hour usage per day.
• Enter the number of days per week you will be using each item to
determine the total watt-hours per week each appliance will require.
* Most appliances have a label on the back that lists the wattage.
Local appliance dealers and the product manufacturers are other
sources of this information.

15. TYPICAL APPLIANCE POWER CONSUMPTION
Appliance Watts
Coffee Pot 200
Coffee Maker 800
Toaster 800-1500
Blender 300
Microwave 600-1500
Hot Plate 1200
Washing Machine Automatic 500
Washing Machine Manual 300
Vacuum Cleaner Upright 200-700
Vacuum Cleaner Hand 100
Sewing Machine 100
Iron 1000
Cloths Dryer Electric 400
Cloths Dryer Gas heated 300-400
Water Pump 250-500
Ceiling Fan 10-50
Table Fan 10-25
Electric Blanket 200
Blow Dryer 1000
Shaver 15
Computer Laptop 20-50
Computer PC 80-150
Computer Printer 100
Typewriter 80-200
TV 25" Color 150
TV 19" Color 70
1TV 2" B&W 20
VCR 40
CD Player 35
Stereo 10-30
Clock Radio 1
Satellite Dish 30
CB Radio 5

16. TYPICAL APPLIANCE POWER CONSUMPTION
Appliance Watts
Lights: 100W Incandescent 100
Lights: 25W Compact Fluorescent 28
Lights: 50W DC Incandescent 50
Lights: 40W DC Halogen 40
Lights: 20W Compact Fluorescent 22
Compact Fluorescent Incandescent: 40 watt equivalent 11
Compact Fluorescent Incandescent: 60 watt equivalent 16
Compact Fluorescent Incandescent: 75 watt equivalent 20
Compact Fluorescent Incandescent: 100 watt equivalent 30
1/4" Drill 250
1/2" Drill 750
1" Drill 1000
9" Disc Sander 1200
3" Belt Sander 1000
12" Chain Saw 1100
14" Band Saw 1100
7-1/4" Circular Saw 900
8-1/4" Circular Saw 1400
Refrig/Freezer 20cf 1.8Kwh per day (15 hours) 540
Refrig/Freezer 16cf 1.6Kwh per day (13 hours) 475
Sunfrost 16cf DC (7 hours) 112
Sunfrost 12cf DC (7 hours) 70
Freezer 14cf (15 hours) 440
Freezer 14cf (14 hours) 350

17. LOAD SIZING WORKSHEET
DC Appliance
Watts x Qty x
Hrs/Day
= Wh/Day x
Days/Wk
= Wh/Wk
A___________
_______________
__
_____________
___
______
B___________
_______________
__
_____________
___
______
C___________
_______________
__
_____________
___
______
D___________
_______________
__
_____________
___
______
E___________
_______________
__
_____________
___
______
Total the numbers in the last column. This is your DC power requirement. TOTAL ______
Multiply the total by 1.3 (I estimate) to compensate for system losses during battery
charge/discharge cycle and other system losses (round trip efficiency).
DC WH/WK
______
1. Add AC WH/WK and DC WH/WK together. This is your total power requirement per week. TOTAL ______
2. Enter the voltage of your battery bank (usually 12 or 24 volts). VOLTS ______
3. Divide line 1 by line 2. This is your amp-hour requirement per week. AH/WK ______
4. Divide line 3 by 7 days. This is your average amp-hour requirement per day that will be used
to size your battery bank and your PV module array. AH/DAY ______

18. OPTIMIZE LOAD CONSUMPTION
• At this point, it is important to examine your power consumption and reduce your power needs
as much as possible. (This is true for any system, but it is especially important for home and
cabin systems, because the cost savings can be substantial.)
• First identify large and/or variable loads (such as water pumps, outdoor lights, electric ranges, AC
refrigerators, clothes washers, etc.) and try to eliminate them or examine alternatives such as
propane or DC models. The initial cost of DC appliances tends to be higher than AC, but you
avoid losing energy in the DC to AC conversion process, and typically DC appliances are more
efficient and last longer.
• Replace incandescent fixtures with fluorescent lights wherever possible. Fluorescent lamps
provide the same level of illumination at lower wattage levels.
• If there is a large load that you cannot eliminate, consider using it only during peak sun hours or
only during the summer. (In other words, be creative!)
• Revise your Load Sizing Worksheet now with your optimized results.

19. SIZING THE BATTERY BANK
• Read an article on "Characteristics of Batteries" and then choose the appropriate battery for your needs. Fill out the
Battery Sizing Worksheet.
• Sizing Your Battery Bank
The first decision you need to make is how much storage you would like your battery bank to provide. Often this is
expressed as “days of autonomy,” because it is based on the number of days you expect your system to provide power
without receiving an input charge from the solar array.
• Temperature Effects
Batteries are sensitive to temperature extremes, and you cannot take as much energy out of a cold battery as a warm
one. Use the chart on the Battery-Sizing Worksheet to correct for temperature effects. Although you can get more than
rated capacity from a hot battery, operation at hot temperatures will shorten battery life. Try to keep your batteries
near room temperature. Charge controllers can be purchased with a temperature compensation option to optimize the
charging cycle at various temperatures and lengthen your battery life.
• Depth of Discharge
Depth of Discharge is the percentage of the rated battery capacity that is withdrawn from the battery. The capability of
a battery to withstand discharge depends on its construction. Two terms, shallow-cycle and deep-cycle, are commonly
used to describe batteries. Shallow-cycle batteries are lighter, less expensive and have a short lifetime. Deep-cycle
batteries should always be used for stand-alone PV systems. These units have thicker plates and most will withstand
daily discharges up to 80% of their rated capacity. The maximum depth of discharge value used for sizing should be the
worst case discharge that the battery will experience. The system control should be set to prevent discharge below this
level.

20. SIZING THE BATTERY BANK…continued
• Rated Battery Capacity
The ampere-hour capacity of a battery is usually specified together with some
standard hour reference such as ten or twenty hours. For example, suppose the
battery is rated at 100 ampere-hours and a 20-hour reference is specified. This
means the battery is fully charged and will deliver a current of 5 amperes for 20
hours. If the discharge current is lower, for example 4.5 amperes, then the capacity
will go to 110 ampere-hours. The relationship between the capacity of a battery and
the load current can be found in the manufacturer’s literature.
• Battery Life
The lifetime of any battery is difficult to predict, because it is dependent on a
number of factors such as charge and discharge rate, depth of discharge, number of
cycles and operating temperature extremes. It would be unusual for a lead-acid
battery to last longer than fifteen years in a PV system but many last for five to eight
years.

21. BATTERY SIZING WORKSHEET
Enter your daily amp-hour requirement. (From the Load Sizing Worksheet, line 4) AH/Day ____
2. Enter the maximum number of consecutive cloudy weather days expected in your area, or the number of days of autonomy you
would like your system to support. Days ___________
3. Multiply the amp-hour requirement by the number of days. This is the amount of amp-hours your system will need to store.
AH ________
4. Enter the depth of discharge for the battery you have chosen. This provides a safety factor so that you can avoid over-draining your
battery bank. (Example: If the discharge limit is 20%, use 0.2.) This number should not exceed 0.8. _______________
Divide line 3 by line 4. AH _________
6. Select the multiplier below that corresponds to the average wintertime ambient temperature your battery bank will experience.
Ambient Temperature Multiplier
80ºF 26.7ºC 1.00
70ºF 21.2ºC 1.04
60ºF 15.6ºC 1.11
50ºF 10.0ºC 1.19
40ºF 4.4ºC 1.30
30ºF -1.1ºC 1.40
20ºF -6.7ºC 1.59

22. BATTERY SIZING WORKSHEET
7. Multiply line 5 by line 6. This calculation ensures that your battery bank will have enough capacity to
overcome cold weather effects. This number represents the total battery capacity you will need.
AH _________
8. Enter the amp-hour rating for the battery you have chosen (use the 20 or 24 hour rate from the battery
manufacturer).
AH____________
9. Divide the total battery capacity by the battery amp-hour rating and round off to the next highest number.
This is the number of batteries wired in parallel required.
____________
10. Divide the nominal system voltage (12V, 24V or 48V) by the battery voltage and round off to the next
highest number. This is the number of batteries wired in series.
____________
11. Multiply line 9 by line 10. This is the total number of batteries required.
____________
• 𝑩𝒂𝒕𝒕𝒆𝒓𝒚 𝑩𝒂𝒏𝒌 𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒚 𝑨𝑯 =
𝑳𝒐𝒂𝒅 𝑾𝑯 ×𝑫𝒂𝒚𝒔 𝒐𝒇 𝑨𝒖𝒕𝒐𝒏𝒐𝒎𝒚×𝑻𝒆𝒎𝒑𝒆𝒓𝒂𝒕𝒖𝒓𝒆 𝑪𝒐𝒓𝒓𝒆𝒄𝒕𝒊𝒐𝒏
𝑫𝒆𝒑𝒕𝒉 𝒐𝒇 𝑫𝒊𝒔𝒄𝒉𝒂𝒓𝒈𝒆 ×𝑺𝒚𝒔𝒕𝒆𝒎 𝑽𝒐𝒍𝒕𝒂𝒈𝒆

23. SIZING THE PV ARRAY
1. Enter your daily amp-hour requirement (From the Load Sizing Worksheet, line 4) AH/Day____
2. Enter the sun-hours per day for your area. Refer to chart.* H/Day_____
3. Multiply Line 2 by 0.85 (for Lesotho climate) to compensate for temperature losses H/DAY_______
4. Divide line 1 by line 3. This is the total amperage required from your solar array. A ____
5. Enter the peak amperage of the solar module you have selected.** Peak A____
6. Divide line 4 by line 5. This is the number of solar modules needed in parallel. _______
7. Select the required modules in series from the following chart. __________
Battery Bank Voltage Number of Modules in Series
12V 1
24V 2
48V 4

24. SIZING THE PV ARRAY…..continued
8. Multiply line 6 by line 7 to find the total number of modules needed
in your array.
Total Number of modules in array _______
9. Enter the nominal power rating (in watts) of the module you have
chosen. W_________
10. Multiply line 8 by line 9. This is the expected power output of your
system. W_________
𝑷𝑽 𝒂𝒓𝒓𝒂𝒚 𝒑𝒐𝒘𝒆𝒓 𝑾 =
𝑳𝒐𝒂𝒅 𝑾𝑯
𝑷𝑺𝑯 × 𝑻𝒆𝒎𝒑𝒆𝒓𝒂𝒕𝒖𝒓𝒆 𝒄𝒐𝒓𝒓𝒆𝒄𝒕𝒊𝒐𝒏

25. *TYPICAL SUNSHINE HOURS FOR MASERU
• The peak sunshine hours (PSH) per day at Maseru are calculated and
shown in detail below.
• The month with the least PSH per day (Design Month) is June
Solar Radiation and PV production characteristics of Maseru
Month Ho [kWh/m2/d] GHI [kWh/m2/d] DHI [kWh/m2/d] K
Average Cell
Temperature
Tc [oC] Tilt Factor
Tilted Plane
Irradiation
(kWh/m2)
Temp.
Correction
Peak
Sunshine
Hours
January 11.91 7.3 2.79 0.613 37 0.89 6.5 0.86 5.59
February 10.93 6.7 2.59 0.613 36 0.96 6.43 0.86 5.53
March 9.48 5.76 1.93 0.607 33 1.06 6.11 0.87 5.34
April 7.61 4.93 1.45 0.648 29 1.24 6.11 0.89 5.44
May 6.06 4.13 0.81 0.692 25 1.44 5.95 0.90 5.35
June 5.29 3.69 0.57 0.697 21 1.58 5.83 0.91 5.31
July 5.55 4.04 0.59 0.727 22 1.56 6.3 0.91 5.74
August 6.8 4.93 0.73 0.725 24 1.35 6.66 0.90 5.99
September 8.59 5.9 1.38 0.686 31 1.14 6.73 0.88 5.92
October 10.29 6.69 2.15 0.650 34 0.99 6.62 0.87 5.76
November 11.57 7.35 2.35 0.636 35 0.9 6.62 0.86 5.69
December 12.13 7.83 2.44 0.646 37 0.86 6.73 0.86 5.79

26. Monthly variation of ambient and cell temperature
0
5
10
15
20
25
30
35
40
Temperature
[oC]
Month
Average daytime cell temperature average ambient temperature

27. **TYPICAL MODULE DATASHEET

28. SIZING THE INVERTER
• An inverter is used in the system where AC power output is needed.
• The input rating of the inverter should never be lower than the total watt of
appliances.
• The inverter must have the same nominal voltage as your battery.
• For stand-alone systems, the inverter must be large enough to handle the total
amount of Watts you will be using at one time.
• The inverter size should be 25-30% bigger than total Watts of appliances.
• In case of appliance type is motor or compressor then inverter size should be
minimum 3 times the capacity of those appliances and must be added to the
inverter capacity to handle surge current during starting.
• For grid tie systems or grid connected systems, the input rating of the inverter
should be same as PV array rating to allow for safe and efficient operation.

29. SIZING THE SOLAR CHARGE CONTROLLER
• A solar charge controller plays a vital role in any solar power system
•Essentially, the charge controller is the regulator that limits the rate of
current that flows to and from the system’s battery bank
• . By controlling the flow of energy from your solar panel array, the solar
charge controller can prevent overcharging issues, thus preventing damage
of the expensive battery
• They also prevent power from flowing backwards to the solar panels at
night, which reduces the impact of phantom battery drain
• They also prevent the battery from over discharging by cutting off the
load when the battery state of charge is below a preset low value
• Despite the fact that the solar charge controller plays such an important
role, very few people know how to accurately determine the correct charge
controller for their solar power kit.

30. What are the Two Types of Solar Charge
Controllers?
•Solar charge controllers are available in two separate
configurations –
Pulse Width Modulation (PWM) charge controller and
 Maximum Power Point Tracking (MPPT) charge controller
•Understanding the differences between the two will help
you determine the best option for the particular needs of
your solar power system.

31. Pulse Width Modulation Charge Controller
(PWM)
• PWM solar charge controllers tend to be less expensive, as they feature
less advanced technology.
• Essentially, a PWM acts as a simple switch, which turns on and off at set
parameters to prevent overcharging issues.
• Using a PWM, the solar panel, or panels, need to be at the same voltage
as the battery, as you connect them (more solar panel connectors types)
directly to the battery with just a switch separating them.
• Since the type of battery bank you are using will determine the output
the solar panels can generate, there is a considerable loss factor, usually
in the range of 30%.

32. Maximum Power Point Tracking Charge
Controller (MPPT)
• MPPT charge controllers are considered ‘smart’ units, as they feature a
built-in computer, which makes them programmable and much more
adaptable than PWM controllers.
• They function by measuring the voltage of the panels and down-convert it
to match the voltage of the battery.
• Since the power flowing into the battery from the charge controller is
dropped to match the battery bank, the current can be raised, which
means more of the available power is flowing from the panels to the
battery.
• Basically, you can use a higher voltage solar array than the voltage of the
battery, which opens up a wide range of options and allows you to make
your solar power system far more effective and even scale it up.

33. The Key Features of a Solar Charge Controller
•Overload Protection – Prevent excessive current that exceeds the amount the circuit can
handle from flowing into your battery. This prevents overheating issues and the premature
deterioration of your battery.
•Low Voltage Disconnection – Automatically disconnects non-critical loads from the battery
when the voltage falls below the necessary amount. This prevents over-discharge issues.
•Prevention of Reverse Current Issues – When the solar panels are no longer generating
power (usually at night), current can flow in the reverse direction, which means electricity will
flow from the battery to the solar array. A charge controller prevents this from happening and
prevents the unnecessary loss of power.
•Advanced Features – More advanced MPPT solar charge controllers often feature display
screens, which allow users to monitor voltage and charge information. They can also permit
multi-stage charging of the battery, meaning they will charge the amount of power sent to the
battery based on its charge level, which helps protect the health of the battery.

34. SUMMARY OF COMPARISONS

35. Solar Charge Controller Sizing
• The first step in sizing your charge controller is determining whether you will be
using a PWM or a MPPT controller, as they are sized differently.
• Charge controllers are sized based on the current and voltage of your solar array
and battery. You will want to choose one that is capable of handling the full
current potential of your solar array, which will maximize your system’s efficiency
and power potential.
• Charge controllers are typically available in 12, 24, and 48 volt varieties.
Amperage ratings will range from 1 to 60 amps.
• Basically, you just need a charge controller that can handle more than your solar
panels can generate. For example, if you use 12v solar panel at 14 amps, you
would need a charge controller that could handle at least 14 amps.
• However, it is a good practice to exceed this minimum (multiply by 1,25), as
environmental factors can cause surges and spikes.

36. Sizing a PWM Charge Controller
• Since they cannot limit their current output, you need to match and preferably exceed the current
of your solar panels.
• When searching for a PWM controller, look for the amperage and voltage rating and make sure
these numbers exceed your solar array’s rating and that of your battery.
• After you have identified the voltage of your system and found a charge controller that matches or
exceeds that value, you need to look at your battery’s rated current.
• This is where we recommend choosing a charge controller that can exceed the amp rating of your
solar array, as it can spike.
• A good practice is to exceed the amp rating by 25%, which means multiplying the amp rating of
your solar panels by 1.25 and finding a charge controller with an amp rating that exceeds that
number.
• If finding a charge controller that matches and exceeds the nominal voltage of your system, the
rated current of your battery, and the maximum solar input seems like a complicated task, do not
worry, it is actually fairly straightforward once you have your numbers.
• However, it is worth noting that the entire process is easier if you opt for an MPPT charge
controller.

37. Sizing a MPPT Charge Controller
• As explained above, MPPT charge controllers regulate output, so they do not need
to be matched to the maximum output of the solar array.
• However, you will still want your MPPT charge controller to exceed the current
potential of your solar array, so it can maximize the efficiency of your system.
• Since MPPT controllers can lower voltage to match the battery bank’s voltage and
increase current to make up for the loss of power, they are far more adaptable.
• You will still want to make sure that your charge controller can allow your system to
run as efficiently as possible, so divide the total wattage of the system by the lower
voltage value between the solar array and battery.
• Follow Watts/Volts to determine the amps.
• So, if you were running a 900W solar array with 48V and your battery’s voltage was
24V, you would divide 900W/24V to get a value of 37.5A. Adding an additional 25%
for potential current spikes would give you a total of 46.9A.
• This would mean choosing a MPPT charge controller that could handle at least 24V
and 50A.

38. Recommended charge controllers, 2021 reviews
SOLAR CHARGE
CONTROLLERS
MAXIMUM CURRENT VOLTAGE RATING WARRANTY
Renogy Wanderer Solar
Charge Controller
10 amps 12 volt, 24 volt -
Victron Energy Solar
Charge Controller
30 amps 12 volt, 24 volt 3 year long
Allpowers Solar Charger
Controller
20 amps 12 volt, 24 volt 1.5 year long
Solarepic Solar Charge
Controller
40 amps 12 volt, 24 volt 2 year long
Powmr Solar Charge
Controller
20 amps 12 volt, 24 volt 1 year long
Mohoo Solar Charge
Controller
30 amps 12 volt, 24 volt -
Binwn Solar Charge
Controller
30 amps 12 volt, 24 volt -
Rich Solar Charge
Controller
40 amps 12 volt, 24 volt 2 year long

39. CLASS EXERCISE
• a) Discuss how a stand alone photovoltaic system works and explain the function of each
component.
• b) Design the required sizes of the PV array, Charge Controller, Storage battery and the
DC/AC inverter for the configuration to power the household AC loads shown on Table 1.
Assume that the DC/DC converter and the charge controller have both an efficiency of 100% (so
they have no effect in influencing the amount of load encountered by the PV array). First
complete Table 1 to get the design load.
• Table 1: PV sizing information
• Peak sunshine hours 5 hours
• System voltage 24 V
• System round trip factor 1.30
• Days of autonomy 2.50
• Maximum Depth of discharge 0.70

40. CLASS EXERCISE .. continued
Available PV module power 250.00 W
• Vmp 35.00 V
• PV temperature correction 0.85
• Available battery size 12 V; 210 AH
• Battery temperature correction 1.20
Appliance
Numb
er
Power
(W)
Total power
(W)
Working
hours
Round trip efficiency
correction
Load
(Wh)
Load
(AH)
Lights 6 20 120 6 1.3 936 39
Refrigerator 1 240 240 10 1.3
TV 1 100 100 5 1.3
Total

41. PV MODULE SPECIFICATIONS

42. HOPPECKE VALVE REGULATED BATTERY
SPECIFICATIONS

43. SUNGROW INVERTER/CHARGER SPECIFICATIONS

44. Solarepic Solar Charge Controller Details
EPEVER MPPT Solar Charge Controller 40A 150V PV Solar Panel Controller Negative Ground W/
MT50 Remote Meter + Temperature Sensor PC Monitoring Cable[Tracer4215BN]
• Negative Grounding MPPT Solar Charge Controller Tracer4215BN, The Advanced MPPT
Control Algorithm makes this 40 Amp MPPT Controller Tracking Efficiency higher than 99.5%
• 150V Max PV Input Allow this Charge Controller Handles More Solar Panels Wiring in Series
to minimize PV current, 5 x 12V Solar Panel Connecting in Series will be applicable
• Work with all Lead Acid Batteries, Sealed AGM GEL and Flooded Battery, User mode allows
buyer setting their own charging parameters.
• RS-485 communication bus interface and Standard MODBUS interface available to meet
various communication requirements, Temperature Sensor and PC monitoring Cable
Attached
• This 40 amp MPPT Solar Panel Charger works with 600W Solar Panel on 12V Battery System
and 1200W on 24V Battery. Max Solar Panel 1560W, multiple load mode allow you set the
load on/off in different situation. A Solid State Relay is recommended if you are using a
Power Inverter