Samlexpower samlexpower SCC-30AB User manual

30 Amp
Solar Charge
Controller
SCC-30AB
Please read this
manual before
operating your
charge controller.
Owner's
Manual

2 | SAMLEX AMERICA INC.
OWNER'S MANUAL | Index
SECTION 1
Safety Instructions................................................................. 3
SECTION 2
General Description of Solar System ................................... 5
SECTION 3
General Information - Batteries ............................................ 8
SECTION 4
Principle of Operation & Features ....................................... 17
SECTION 5
Contruction, Layout and Controls ...................................... 29
SECTION 6
Installation & Operation ..................................................... 34
SECTION 7
Troubleshooting Guide ....................................................... 42
SECTION 8
Specications ..................................................................... 44
SECTION 9
Warranty ........................................................................ 45
Disclaimer of Liability
UNLESS SPECIFICALLY AGREED TO IN WRITING, SAMLEX AMERICA INC.:
1. MAKES NO WARRANTY AS TO THE ACCURACY, SUFFICIENCY OR SUITABILITY OF ANY TECHNICAL OR OTHER INFORMATION
PROVIDED IN ITS MANUALS OR OTHER DOCUMENTATION.
2. ASSUMES NO RESPONSIBILITY OR LIABILITY FOR LOSSES, DAMAGES, COSTS OR EXPENSES, WHETHER SPECIAL, DIRECT,
INDIRECT, CONSEQUENTIAL OR INCIDENTAL, WHICH MIGHT ARISE OUT OF THE USE OF SUCH INFORMATION. THE USE OF
ANY SUCH INFORMATION WILL BE ENTIRELY AT THE USERS RISK.
Samlex America reserves the right to revise this document and to periodically make changes to the content
hereof without obligation or organization of such revisions or changes.
Copyright Notice/Notice of Copyright
Copyright © 2021 by Samlex America Inc. All rights reserved. Permission to copy, distribute and/or modify this
document is prohibited without express written permission by Samlex America Inc.

2 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 3
SECTION 1 | Safety Instructions
Please read these instructions before installing or operating the Charge Controller to
prevent personal injury or damage to the Charge Controller.
Installation and wiring compliance
• Installation and wiring must comply with the local and National Electrical Codes
and must be done by a certied electrician.
Preventing electrical shock
• The negative system conductor should be properly grounded. Grounding should
comply with local codes.
• Disassembly / repair should be carried out by qualied personnel only.
• Disconnect all input and output side connections before working on any circuits
associated with the Charge Controller. Turning the on/off control on the Charge
Controller to off position may not entirely remove dangerous Voltages.
• Be careful when touching bare terminals of capacitors. The capacitors may retain
high lethal Voltages even after the power has been removed. Discharge the
capacitors before working on the circuits.
Installation environment
• The Charge Controller should be installed indoor only in a well ventilated, cool, dry
environment.
• Do not expose to moisture, rain, snow or liquids of any type.
Preventing re and explosion hazards
• Working with the Charge Controller may produce arcs or sparks. Thus, the Charge
Controller should not be used in areas where there are inammable materials or
gases requiring ignition protected equipment. These areas may include spaces con-
taining gasoline powered machinery, fuel tanks, battery compartments.
Precautions when working with batteries
• Batteries contain very corrosive, diluted sulphuric acid as electrolyte. Precautions
should be taken to prevent contact with skin, eyes or clothing.
• Batteries generate hydrogen and oxygen during charging, resulting in evolution of
explosive gas mixture. Care should be taken to ventilate the battery area and fol-
low the battery manufacturer’s recommendations.
• Never smoke or allow a spark or ame near the batteries.
• Use caution to reduce the risk of dropping a metal tool on the battery. It could spark
or short circuit the battery or other electrical parts and could cause an explosion.
• Remove metal items like rings, bracelets and watches when working with batteries.
The batteries can produce a short circuit current high enough to weld a ring or the
like to metal and cause a severe burn.
• If you need to remove a battery, always remove the ground terminal from the bat-
tery rst. Make sure that all the accessories are off so that you do not cause a spark.

4 | SAMLEX AMERICA INC.
SECTION 1 | Safety Instructions
Charge Controller related
• Please ensure the input Voltage fed to the Charge Controller does not exceed
50 VDC to prevent permanent damage to the Charge Controller. Ensure that the
maximum Open Circuit Voltage Voc of the 12V nominal Solar Panel / Solar Array is
less than 50V. If two 12V nominal Solar Panels are being used in series to make a
24V nominal Solar Array, make sure that the maximum Open Circuit Voltage Voc of
each of the 12 V Panels is less than 25V.
• Do not exceed the maximum current rating of 30 A.
• Do not exceed a Battery Voltage of 24V (nominal) . Do not use a battery less than 12V.
• Charge only 12 or 24V (nominal) Lead Acid batteries or Lithium batteries designed
for lead acid drop-in replacement. Charge settings (Dip Switch) must be set in ac-
cordance with battery manufacturer’s recommendations.
• The controller should be protected from direct sunlight. Ensure adequate space for
air ow around the controller’s face plate.
• Do not install in a sealed compartment with batteries.
• Never allow the solar array to be connected to the controller with the battery dis-
connected. This can be a dangerous condition with high open-circuit solar voltage
present at the terminals.
• Use only copper wire with minimum 75°C insulation rating, and between 10 AWG
(5.2 mm2) and 14 AWG (2.1 mm2) gauge.
• The Negative system conductor should be properly grounded. Grounding should
comply with local codes.

4 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 5
SECTION 2 | General Description of Solar System
Current (I),Voltage (V) and Power (P) Curves of a Solar Panel
and how the Solar Panel is rated - Voc , Vmp , Isc , Imp , Pmax
Fig. 2.1. Current (I),Voltage (V) and Power (P) Curves
A Current (I) versus Voltage (V) Curve of a Solar Panel (“I-V” Curve) shows the possible
combinations of its current and Voltage outputs. A typical I-V curve for a 12V Panel is
shown in Fig. 2.1.
The power in a DC electrical circuit is the product of the Voltage and the current.
Mathematically,
• Power (P) in Watts (W) = The Current (I) in Amperes (A) X the Voltage (V) in
Volts (V) i.e. W = V x A
A Solar Panel produces its maximum current when there is no resistance in the circuit,
i.e. when there is a short circuit between its Positive and Negative terminals. This
maximum current is known as the Short Circuit Current and is abbreviated as Isc. When
the Panel is shorted, the Voltage in the circuit is zero.
Conversely, the maximum Voltage occurs when there is a break in the circuit. This is
called the Open Circuit Voltage (Voc). Under this condition, the resistance is innitely
high and there is no current, since the circuit is incomplete. Typical value of the open-
circuit Voltage is located about 0.5 – 0.6V per cell for Crystalline Cells and 0.6 – 0.9V
for Amorphous Cells. Normally, 12V nominal panel consists of 36 cells in series and a
24V nominal panel consists of 72 cells in series. Hence, the Open Circuit Voltage (Voc)
of panels with crystalline cells will be as follows:
- 12V panel: 36 cells x (0.5 to 0.6V per cell) = 18V to 21.6V
- 24V panel: 72 cells x (0.5 to 0.6V per cell) = 36V to 43.2V
These two extremes in load resistance, and the whole range of conditions in between
them, are depicted on the I-V Curve. Current, expressed in Amps, is on the vertical
Y-axis. Voltage, inV, is on the horizontal X-axis.

6 | SAMLEX AMERICA INC.
The power available from a photovoltaic device at any point along the curve is just the
product of Current (I) in Amps (A) and voltages (V) at that point and is expressed in
Watts. At the short circuit current point, the power output is zero, since the voltage is
zero. At the open Circuit Voltage point, the power output is also zero, but this time it
is because the current is zero.
Maximum Power Point and Rated Power of Solar Panel
There is a point on the knee of the I-V Curve where the maximum power output is
located and this point is called the Maximum Power Point (MPP). The voltage and
current at this Maximum Power Point are designated as Vmp and Imp.
The values of Vmp and Imp can be estimated from Voc and Isc as follows:
Vmp ≈(0.75 – 0.9) Voc
Imp ≈ (0.85 – 0.95) Isc
The rated power of the Solar Panel in Watts (Pmax) is derived from the above values
of voltage Vmp and current Imp at this Maximum Power Point (MPP):
• Rated power in Watts, Pmax = Vmp X Imp
Example of I-V Curve and Ratings of a 12V Solar Panel
= 2.5A
= 17A
=
=
= 2.7A
= 21V
Fig. 2.2. Example of I-V Curve and Ratings of a 12V PV / Solar Panel
I-V Curve for a typical 12V Solar Panel is shown in Fig. 2.2. The Open Circuit Voltage Voc
is 21V and the Short Circuit Current Isc = 2.7V.
Maximum Power Point in the example curve given above is where Vmp is 17V, and the
current Imp is 2.5A. Therefore, the rated or the maximum power Pmax in watts is 17V
times 2.5A, or 42.5 Watts.
SECTION 2 | General Description of Solar System

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Standard Test Conditions (STC) for Specifying Solar Panels
The I-V curve is also used to compare the performance of Solar Panel. The curve is,
therefore, generated based on the performance under Standard Test Conditions (STC)
of sunlight and device temperature of 25°C. It assumes there is no shading on the
device. Standard sunlight conditions on a clear day are assumed to be 1,000 Watts of
solar energy per square meter (1000 W/m2or 1 kW/m2). This is sometimes called one
sun, or a peak sun. Less than one sun will reduce the current output of the PV device
by a proportional amount. For example, if only one-half sun: (500 W/m2) is available,
the amount of output current is roughly cut in half.
Factors Affecting Voltage and Current Output of Solar Cell
The amount of electric current generated by photon excitation in a Solar Cell at a
given temperature is affected by the incident light in two ways:
• By the intensity of the incident light.
• By the wavelength of the incident rays.
The materials used in Solar Cells have different spectral responses to incident light,
and exhibit a varying sensitivity with respect to the absorption of photons at given
wavelengths.Each semiconductor material will have an incident radiation threshold
frequency, below which no electrons will be subjected to the photovoltaic effect.
Above the threshold frequency, the kinetic energy of the emitted photoelectron varies
according to the wavelength of the incident radiation, but has no relation to the light
intensity. Increasing light intensity will proportionally increase the rate of photoelectron
emission in the photovoltaic material. In actual applications, the light absorbed by
a solar cell will be a combination of direct solar radiation, as well as diffused light
bounced off of surrounding surfaces. Solar Cells are usually coated with anti-reective
material so that they absorb the maximum amount of radiation possible.
The output current of the Solar Panel can increase due to what is known as the “Edge
of the Cloud Effect”. As the sun moves into a hole between the clouds, your solar
panels will see full direct sunlight combined with reected light from the clouds! They
will absorb more energy than they could on a cloudless day! Thus, a factor of 1.25
times the Short Circuit Current Isc is recommended when sizing the current capacity
of the Charge Controller.
The output current of the Solar Cell has a Positive Temperature Coefcient – the
output current increases with the rise of temperature. However, it is negligible – less
than 0.1 % / °C of the Short Circuit Current Isc.
The output Voltage of the Solar Cell has a Negative Temperature Coefcient – The
output Voltage increases with decrease in temperature. For example, a Silicon Cell
has a Temperature Coefcient of – 2.3 mV / °C / Cell. Hence, during cold winter days,
the voltage will rise. As a Rule of Thumb, the voltage rating of the Charge Controller
should be sized as 1.25 times the Open Circuit Voltage rating Voc of the Solar
Panel to ensure that the Charge Controller is not damaged due to over voltage.
SECTION 2 | General Description of Solar System

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Battery Types
This charge controller is suitable to support the following battery technologies.
Sealed Lead Acid (SLA) or Valve regulated Lead Acid (VRLA) Batteries
Sealed Lead Acid (SLA) batteries or Valve Regulated Lead Acid (VRLA) batteries can
either be Gel Cell or AGM (Absorbed Glass Mat). In a Gel Cell battery, the electrolyte
is in the form of a gel. In AGM (Absorbed Glass Mat) battery, the electrolyte is soaked
in Glass Mat. In both these types, the electrolyte is immobile. There are no rell caps
and the battery is totally sealed. Hydrogen and Oxygen released during the charging
process are not allowed to escape and are recombined inside the battery. Hence, there
is no water loss and the batteries are maintenance free. These batteries have safety
valves on each cell to release excessive pressure that may be built up inside the cell.
The Gel Cell is the least affected by temperature extremes, storage at low state of
charge and has a low rate of self discharge. An AGM battery will handle overcharging
slightly better than the Gel Cell.
Non Sealed (Vented / Flooded / Wet Cell) Lead Acid Batteries
In a non-sealed / vented / ooded / wet cell battery, each individual cell compartment
has a rell cap that is used to top up the cell with distilled water and to measure
the specic gravity of the electrolyte using a hydrometer. When fully charged, each
individual cell has a voltage of approximately 2.105V and electrolyte specic gravity
of 1.265. As the cell discharges, its voltage and specic gravity drop. Thus, a healthy,
fully charged, 12V nominal battery with each of the 6 cells fully charged to 2.105V
will measure a Standing Voltage of 12.63V at 25ºC / 77ºF. Also, in a healthy battery,
all the individual cells will have the same voltage and same specic gravity. If there is
a substantial difference in the voltages (0.2V or higher) and specic gravities of the
individual cells, the cells will require equalization.
SLI (Starting, Lighting, Ignition) Batteries
SLI batteries that are used for automotive starting, lighting, ignition and powering
vehicular accessories. SLI batteries are designed to produce high power in short bursts
for cranking. SLI batteries use lots of thin plates to maximize the surface area of the
battery for providing very large bursts of current (also specied as Cranking Amps).
This allows very high starting current but causes the plates to warp when the battery is
cycled. Vehicle starting typically discharges 1%-3% of a healthy SLI battery’s capacity. The
automotive SLI battery is not designed for repeated deep discharge where up to 80% of
the battery capacity is discharged and then recharged. If an SLI battery is used for this
type of deep discharge application, its useful service life will be drastically reduced.
This type of battery is not recommended for the storage of energy for DC powered
devices like lighting, radios, inverters, etc. However, they are recommended as
starting battery for the back-up generator.
Deep Cycle Lead Acid Batteries
Deep cycle batteries are designed with thick-plate electrodes to serve as primary
power sources, to have a constant discharge rate, to have the capability to be deeply
SECTION 3 | General Information: Batteries

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SECTION 3 | General Information: Batteries
discharged up to 80% capacity and to repeatedly accept recharging. They are
marketed for use in recreation vehicles (RV), boats and electric golf carts – so they may
be referred to as RV batteries, marine batteries or golf cart batteries.
Lithium Battery
Lithium batteries designed for lead acid drop-in replacement are supported by this
charge controller in a 12V nominal or 24V nominal conguration. Ensure that the
manufacturers recommended charge voltages are congured accordingly on the
Charge Controller Dip Switch. Temperature compensation and Equalization should
not be used with Lithium batteries.
Units of Battery Capacity – Ampere Hours (Ah) and Reserve Minutes (RC)
Battery capacity is the measure of electrical energy the battery can store and deliver
to a load. It is determined by the amount of current any given battery can deliver
over a stipulated period of time. The energy rating is expressed in Ampere Hours (Ah).
Normally, Ah capacity is rated at 20 Hour discharge rate i.e., the number of Amperes of
current the battery can deliver for 20 Hours at 80ºF (26.7ºC) till the voltage drops to 10.5V
for 12V battery and 21V for 24V battery. For example, a 100 Ah battery will deliver 5
Amperes for 20 Hours
Battery capacity is also expressed as Reserve Capacity (RC) in minutes. Reserve
capacity is the time in minutes for which the battery can deliver 25 Amperes
at 80ºF (26.7ºC) till the voltage drops to 10.5V for 12V battery and 21V for 24V
battery. Approximate relationship between the two units is as follows:
Capacity in Ah = Reserve Capacity in RC minutes x 0.6
Typical Battery Sizes
The Table below shows details of some popular battery sizes:
BCI* GROUP BATTERY VOLTAGE, V BATTERY CAPACITY, Ah
27 / 31 12 105
4 D 12 160
8D 12 225
GC2** 6 220
* Battery Council International ** Golf Cart
Table 3.1. Popular Battery Sizes

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SECTION 3 | Description & Principle of Operation
Reduction in Usable Capacity at Higher Discharge Rates
As stated above, the rated capacity of the battery in Ah is normally applicable at a
discharge rate of 20 Hours. As the discharge rate is increased, the usable capacity
reduces due to “Peukert Effect”. This relationship is not linear but is more or less
according to the Table below:
HOURS OF
DISCHARGE
DISCHARGE
RATE
DISCHARGE RATE
FOR 100Ah BATTERY
USABLE
CAPACITY
20 HRS. C/20 A 5A 100 %
10 HRS. C/10 A 10A 87 %
8 HRS. C/8 A 12.5A 83 %
6 HRS. C/6 A 16.7A 75 %
5 HRS. C/5 A 20A 70 %
3 HRS. C/3 A 33.3A 60 %
2 HRS. C/2 A 50A 50 %
1 HRS. C A 100A 40 %
Table 3.2. Battery Capacity versus Rate of Discharge
Using the above Table will show that a 100 Ah capacity battery will deliver 100% (i.e.
full 100 Ah) capacity if it is slowly discharged over 20 hours at the rate of C/20 A or 5A.
However, if it is discharged at a rate of 2 Hrs. (C/2A or 50A) then theoretically, it should
provide 100 Ah ÷ 50A = 2 Hours. However, the Table above shows that for 2 Hours
discharge rate (C/2A or 50A), the capacity is reduced to 50% (i.e. 50 Ah). Therefore, at 50
Ampere discharge rate the battery will actually last for 50 Ah ÷ 50A = 1 Hour.
State of Charge (SOC) of a Battery
The “Standing Voltage” of a battery can approximately indicate the State of Charge
(SOC) of the battery. The “Standing Voltage” is measured after disconnecting any
charging device(s) and the battery load(s) and letting the battery “stand” idle for 3 to
8 hours before the voltage measurement is taken. Table 3.3 shows the State of Charge
versus Standing Voltage for a 12V lead acid battery system (6 cells in series) at around
80ºF (26.7ºC). For 24-volt systems, multiply by 2 (12 cells in series); for 48-volt systems,
multiply by 4 (24 cells in series).

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SECTION 3 | Description & Principle of Operation
PERCENTAGE OF
FULL CHARGE
STANDING VOLTAGE OF
12V NOMINAL BATTERY
Cell Voltage (12V BATTERY
HAS 6 CELLS IN SERIES)
100% 12.63V 2.105V
90% 12.6V 2.10V
80% 12.5V 2.08V
70% 12.3V 2.05V
60% 12.2V 2.03V
50% 12.1V 2.02V
40% 12.0V 2.00V
30% 11.8V 1.97V
20% 11.7V 1.95V
10% 11.6V 1.93V
0% = / < 11.6V = / < 1.93V
Table 3.3. State of Charge versus Standing Voltage – 12V Battery
Check the individual cell Voltages. If the inter cell Voltage difference is more than a
0.2V, the battery will have to be equalized. Please note that only the non-sealed /
vented / ooded / wet cell batteries are equalized. Do not equalize sealed / VRLA type
of AGM or Gel Cell Batteries (unless allowed by the manufacturer).
Battery Efciency
A lead-acid battery has an efciency of only 75% - 85%. The energy lost appears as
heat and warms the battery. This means that the Ampere Hour (Ah) energy required
to charge a battery to its full rated capacity will be approximately 120% to 130%
higher than the Ah capacity rating of the battery.
Depth of Discharge and Battery Life
The deeper a battery is discharged on each cycle, the shorter the battery life. Using
more batteries than the minimum required will result in longer life for the battery
bank. A typical life cycle chart is given in the Table below:
DEPTH OF DISCHARGE
% OF AhCAPACITY
CYCLE LIFE OF
GROUP 27 / 31
CYCLE LIFE OF
GROUP 8D
CYCLE LIFE OF
GROUP GC2
10 1000 1500 3800
50 320 480 1100
80 200 300 675
100 150 225 550
It is recommended that the depth of discharge should be limited to 50%.
Table 3.4. Typical Cycle Life Chart
Effect of Temperature on Lead Acid Batteries
The charging characteristics of the battery will vary with temperature. This is nearly
linear and the Voltage Coefcient of Temperature Change is normally taken as -3
mV to -5 mV / ºC / Cell. The charging voltage is required to be reduced and as the
temperature is decreased, the charging voltage has to be increased.

12 | SAMLEX AMERICA INC.
All charging voltage set points are normally specied at 25ºC / 77ºF. In solar systems,
battery temperatures often vary up to 15ºC from the 25ºC reference. The Absorption,
Float and Equalization Voltages must then be adjusted or a controller with Temperature
Sensor should be used. Table below shows example of adjustments for Absorption
Voltage of say 14.4V for 12V battery, (based on Voltage Coefcient of Temperature
Change as -5 mV / ºC / Cell or -30mV (.03V) for a 6 cell, 12V battery).
BATTERY TEMPERATURE ABSORPTION VOLTAGE (12V BATTERY)
40ºC 13.95V
25ºC (Reference) 14.4V (Reference)
10ºC 14.85V
Table 3.5. Absorption Voltage vs Temperature (example)
In case temperature compensation is not provided, the warmer battery at 40ºC will
begin to heat and outgas at 13.95V and will continue to overcharge until the non-
compensated Absorption Voltage set point is reached (14.4V). In cooler temperatures,
the 10ºC battery will experience severe undercharging, resulting in sulfation.
It is recommended that a battery charger / charge controller with a provision for
temperature sensing and compensation should be used if the battery electrolyte
temperature varies more than 5ºC to 10ºC (9ºF to 18ºF).
Loss of Battery Capacity at Low Temperatures
Batteries lose capacity in low temperatures. At 32ºF (0ºC), a battery will deliver about 70 to
80% of its rated capacity at 80ºF (26.7ºC). If the electrolyte temperature of the battery bank
is lower than 80ºF (26.7ºC), additional batteries will be needed to provide the same usable
capacity. For very cold climates, an insulated / heated battery compartment is recommended.
Freezing of Electrolyte
For applications with low ambient temperature, the lead-acid battery must also be
protected against freezing of the electrolyte. The risk of freezing depends on the
state of charge. The chart given below illustrates the freezing limit as a function of
the state of charge.
-80°
-60°
-40°
-20°
0°
020 40 60 80 100
State of charge [%]
Temperature [°C]
slushy until hard
-80°
-60°
-40°
-20°
0°
020 40 60 80 100
State of charge [%]
Temperature [°C]
slushy until hard
STATE OF CHARGE (%)
TEMPERATURE (ºC)
Fig 3.1. Temperature vs State of Charge
SECTION 3 | Description & Principle of Operation

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SECTION 3 | Description & Principle of Operation
Series and Parallel Connection of Batteries
Series Connection
Solar Charge Controller
SCC30-AB (rear view)
PV +
PV -
BAT+
BAT - 6V Battery 6V Battery
Battery 4 Battery 3
6V Battery
Battery 2
6V Battery
Battery 1
6V Battery
Cable “A”
Cable “B”
Fig. 3.2. Series Connection
When two or more batteries are connected in series, their voltages add up, but their Ah
capacity remains the same. Fig. 3.2 above shows 4 pieces of 6V, 200 Ah batteries connected
in series to form a battery bank of 24V with a capacity of 200 Ah. The Positive terminal of
Battery 4 becomes the Positive terminal of the 24V bank. The Negative terminal of Battery
4 is connected to the Positive terminal of Battery 3. The Negative terminal of Battery
3 is connected to the Positive terminal of Battery 2. The Negative terminal of Battery
2 is connected to the Positive terminal of Battery 1. The Negative terminal of Battery 1
becomes the Negative terminal of the 24V battery bank.
Parallel Connection
Solar Charge Controller
SCC30-AB (rear view)
PV +
PV -
BAT+
BAT - 12V Battery 12V Battery 12V Battery 12V Battery
Battery 1 Battery 3Battery 2 Battery 4
Cable “A”
Cable “B”
Fig. 3.3. Parallel Connection
When two or more batteries are connected in parallel, their voltage remains the same
but their Ah capacities add up. Fig. 3.3 above shows 4 pieces of 12V, 100 Ah batteries
connected in parallel to form a battery bank of 12V with a capacity of 400 Ah. The
four Positive terminals of Batteries 1 to 4 are paralleled (connected together) and this
common Positive connection becomes the Positive terminal of the 12V bank. Similarly,
the four Negative terminals of Batteries 1 to 4 are paralleled (connected together)
and this common Negative connection becomes the Negative terminal of the 12V
battery bank.

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Series – Parallel Connection
Solar Charge Controller
SCC30-AB (rear view)
PV +
PV -
BAT+
BAT - 6V Battery 6V Battery 6V Battery 6V Battery
String 1 String 2
Battery 1 Battery 3Battery 2 Battery 4
Cable “A”
Cable “B”
Fig. 3.4. Series-Parallel Connection
Figure 3.4 above shows a series – parallel connection consisting of four 6V, 200 Ah
batteries to form a 12V, 400 Ah battery bank. Two 6V, 200 Ah batteries, Batteries 1
and 2 are connected in series to form a 12V, 200 Ah battery (String 1). Similarly, two
6V, 200 Ah batteries, Batteries 3 and 4 are connected in series to form a 12V, 200 Ah
battery (String 2). These two 12V, 200 Ah Strings 1 and 2 are connected in parallel to
form a 12V, 400 Ah bank.
!
CAUTION!
When 2 or more batteries / battery strings are connected in parallel and are
then connected to a charger (See Fig. 3.3 and 3.4), attention should be paid
to the manner in which the charger is connected to the battery bank. Please
ensure that if the Positive output cable of the battery charger (Cable “A”) is
connected to the Positive battery post of the rst battery (Battery 1 in Fig. 3.3)
or to the Positive battery post of the rst battery string (Battery 1 of String 1
in Fig. 3.4), then the Negative output cable of the battery charger (Cable “B”)
should be connected to the Negative battery post of the last battery (Battery
4 as in Fig. 3.3) or to the Negative Post of the last battery string (Battery 4 of
Battery String 2 as in Fig. 3.4). This connection ensures the following:
• The resistances of the interconnecting cables will be balanced.
• All the individual batteries / battery strings will see the same series resistance.
• All the individual batteries will charge at the same charging current and
thus, will be charged to the same state at the same time.
• None of the batteries will see an overcharge condition.
If the Positive output cable of the battery charger (Cable “A”) is connected
to the Positive battery post of the rst battery (Battery 1 in Fig. 3.3) or to
the Positive battery post of the rst battery string (Battery 1 of String 1 in
Fig. 3.4), and the Negative output cable of the battery charger (Cable “B”)
is connected to the Negative battery post of the rst battery (Battery 1 as
in Fig. 3.3) or to the Negative Post of the rst battery string (Battery 1 of
Battery String 1 as in Fig. 3.4), the following abnormal conditions will result:
SECTION 3 | Description & Principle of Operation

14 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 15
• The resistances of the connecting cables will not be balanced.
• The individual batteries will see different series resistances.
• All the individual batteries will be charged at different charging current
and thus, will reach fully charged state at different times.
• The battery with lower series resistance will take shorter time to charge
as compared to the battery which sees higher series resistance and
hence, will experience over charging and its life will be reduced.
Sizing the Battery Bank
The capacity of the battery bank in Ampere Hours (Ah) is determined based on the
amount of energy that is required to be provided for operating the desired DC and AC
loads for desired span of time in hours.
For example, backup energy may be required for say 4 hours or 1 day (24 Hours) or 3
days (72 Hours). In this connection, the following formulae will be applicable:
FORMULA 1 DC Power in Watts (W) DC Volts (V) x DC Current (A)
FORMULA 2 AC Power in watts (W) AC Volts (V) x AC current (A) x Power
Factor (0.8 Typical)
FORMULA 3 DC Power drawn from the Battery by DC load fed directly
from the battery
Power of DC load in Watts (W)
FORMULA 4 DC power drawn from the battery by AC load fed from
DC-AC inverter
1.2 x Power of AC load in Watts (W)
(Assuming typical efciency of
inverter = 84%)
FORMULA 5 Energy consumption from the
battery in Watt Hour (Wh) Power in Watts (W) x time in Hours (h)
FORMULA 6 Energy consumption from the
battery in Ampere Hour (Ah)
12v
Battery
Energy consumption in
Watt-Hour (Wh) ÷ 12
24v
Battery
Energy consumption in
Watt-Hour (Wh) ÷ 24
Table 3.6. Battery Sizing Formulas
Determining Total Battery Energy Consumption – First step is to determine the total
battery energy consumption in Ampere Hours for running the desired AC and DC
loads during the desired span of backup time:
a) Find out the power rating of each AC and DC device in Watts (W). If Watt
rating is not available, calculate the Watt rating using Formulae 1 or 2.
b) Determine / calculate the power drawn from the battery in Watts (W) by
each of the AC and DC devices. For DC devices, this will be the same as its DC
Power rating (Formula 3). For AC devices powered from DC to AC inverter,
use Formula 4 to calculate the power drawn in Watts (W) from the battery.
SECTION 3 | Description & Principle of Operation

16 | SAMLEX AMERICA INC.
c) Calculate the energy consumption in Watt-Hours (Wh) for each load using
Formula 5 based on the number of hours each load is expected to run during
the desired span of backup time. Add all to get the total energy in Watt
Hours (Wh).
d) Calculate the total battery energy consumption in Ampere Hours (Ah) for
the combined DC and AC loads using Formula 6.
Determining Actual Ah Capacity of Battery Bank – Actual Ah capacity of the battery
bank is determined based on the following considerations:
e) As pointed out under heading “Reduction in Usable Capacity at Higher
Discharge Rates” on page 10, the Ah capacity of a battery is normally
specied at slower C/20 A i.e. 20 Hour discharge rate. However, in backup
applications, batteries get discharged at much higher discharge rates.
Normally, 3 Hour i.e. C/3 A Discharge Rate is considered for this application.
As per Table 3.2, the usable capacity at this higher discharge rate will be
reduced to 60%. The actual capacity of the battery will have to be increased
by 1.66 times.
f) Further, for longer battery life, the battery should not be discharged deeply
(Please refer to heading “Depth of Discharge and Battery Life” on page 11).
Normally, depth of discharge should be limited to 80%. Hence, the actual
battery capacity will have to be increased to 1.25 times the backup energy
consumption to compensate for this limitation.
g) The actual battery capacity will, therefore, be equal to 1.66 x 1.25 = 2.07
times or say 2 times.
h) For example, if the total battery energy consumption as per the above
calculation at (d) is say 200 Ah, the capacity of the battery bank will be 2 x
200Ah = 400Ah.
Requirements of Battery Charging in Solar Systems
Batteries in Solar Systems are commonly subject to abusive conditions that are
generally due to:
• Under charging due to low sun peak hours
• Excessive charging in high sun peak hours
• Inappropriate or ineffective charge control for the battery technology
The individual or combined effects of sun peak hour changes, poor charge control and
the daily load changes can be potentially damaging to the battery. Cheaper charge
control strategies such as simple ON/OFF PV array shedding (Non PWM control) will
generally provide the battery with sufcient charging current to complete the Bulk
Charge Phase which will return the battery to 80% State of Charge. After the Bulk
Charge Phase, the Taper or Absorption Charge Phase is very important in preventing
stratication, hard sulfation and pre-mature capacity loss.
SECTION 3 | Description & Principle of Operation

16 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 17
SCC-30AB is a Series Type of PWM (Pulse Width Modulation) Solar Charge Controller.
It is based on an advanced design using a micro-controller for digital accuracy and
fully automatic operation. It can be used for 12V or 24V battery systems. PWM battery
charging has been optimized for longer battery life. The unit is designed for user-
friendly operation.
Features
• Microcontroller based, high performance design for digital accuracy and fully
automatic and intelligent operation
• Dual Voltage capability – can be used with 12V / 24V Solar Systems
• 30A charging capacity
• Series Mode PWM (Pulse Width Modulation) charging design at optimum PWM
frequency of 300 Hz for low loss, higher efciency charging and longer battery life
• 4 Stages of charging for 100% return of capacity and long battery life – Bulk,
Absorption, Float and Equalization Stages
• Choice of 8 sets of Absorption / Float / Equalization Voltage settings to enable
complete and safe charging of a wide range of Lead Acid and Lithium Batteries
• Convenient 2 x 16 character LCD Display with backlight for display of operating
information and data. Additional LED indication for displaying the charging stages
• Remote Battery Temperature Sensor (BTS) Model 30AB-TS for temperature
compensation to ensure improved charging of batteries that experience wider
temperature variations during the year
• Specially designed for RVs, boats and trucks – allows convenient and aesthetic
ush mounting on walls / panels
Principle of Operation of Solar Charging with Series Type
Pulse Width Modulation (Pwm) Control
The design and operation of SCC-30AB is based on Series Type PWM (Pulse Width Modu-
lation) control at PWM frequency of 300 Hz.
PWM Explanation
In order to understand the working of the controller, it is necessary to understand the
concept of PWM and Duty Cycle, which are explained with the help of Fig. 4.1. The
explanation is based on Series Type of PWM control
The output of the solar panel is connected to the battery in series with a Switch.
Controlled ON / OFF operation of the Switch is used to control the current and the
voltage to charge the battery.
SECTION 4 | Principle of Operation & Features

18 | SAMLEX AMERICA INC.
SECTION 4 | Principle of Operation & Features
Fig. 4.1. Series Type PWM Control - PWM Frequency = 300 Hz
2.7A
A
0PULSE PERIOD = 3.33 ms
OFF = 2.5 msON = 0.83 ms
AVERAGE = 0.675A
Pulse Width = ON Time
FREQUENCY = % DUTY CYCLE =
1
PULSE
PERIOD
1
3.33 ms = 300 Hz PULSE WIDTH PULSE PERIOD
0.83 ms
3.33 ms = 25%=
=
SOLAR
PANEL
BATTERY
SERIES
MOSFET
SWITCH
A solar panel is a current source that outputs almost constant current equal to its
Short Circuit Current (ISC) over a wide voltage range (provided incident light, cell
temperature and air mass remain constant). For example, please refer to Fig 2.2 at
page 6 which shows Current versus Voltage Curve of a 12V nominal, 42.5W solar panel
at Standard Test Conditions (Incident sunlight of 1000 W/m², cell temperature of 25°C
and Air Mass of 1.5). It will be seen that Short Circuit Current (ISC) of 2.7A is almost
constant over voltage range from 0V to around 15V.
In the example shown in Fig. 4.1 above, the switch is fed with constant Short Circuit
Current (ISC) of 2.7A of the 42.5W panel. 2 PWM output current pulses of the Switch at
frequency of 300 Hz and Duty Cycle of 25% are shown.
PWM consists of repetitive cycles of controlled duration of ON and OFF states of the
Switch. The Pulse Period of one cycle of 300 Hz PWM is the total combined duration
of ON and OFF states of the Switch which is 3.33 ms. Number of cycles of switching per
second is called the PWM Frequency. Mathematically, Frequency = (1 ÷ Pulse Period
“T”) and is 300 Hz in this case (1÷ 33.3 ms = 300 Hz). The duration of ON state is also
called the “Pulse Width”. In PWM control, the duration of the Pulse Width is varied
(modulated) and is dened by “Duty Cycle” which is the ratio of the “ON Time” to
the “Pulse Period ”. Duty Cycle is normally specied in %. Thus, 0% Duty Cycle will
mean that the switch is constantly OFF (will output 0A) and 100% Duty Cycle will
mean that the switch is constantly ON (will output the full Short Circuit Current (ISC)
i.e. 2.7A in the above example). For Duty Cycles > 0% and < 100%, the switch will
alternate between ON and OFF states in a controlled manner in every cycle and will
output variable current within a range of slightly higher than 0A to slightly less than
the full Short Circuit Current (ISC) i.e. 2.7A in the above example.

18 | SAMLEX AMERICA INC. SAMLEX AMERICA INC. | 19
SECTION 4 | Principle of Operation & Features
Through PWM control, the Switch converts constant Short Circuit Current (ISC) at
its input to controlled average current at its output by varying the Duty Cycle. The
average value of output current of the Switch is equal to the constant input value of
Short Circuit Current (ISC) multiplied by the Duty Cycle. Fig 4.1 above shows an example
where 2.7A constant input Short Circuit Current (ISC) is reduced to average of 25% or
to 0.675A by switching the 2.7A constant Short Circuit Current (ISC) ON and OFF at 25%
Duty Cycle.
PWM Charging in SCC-30AB
Battery charging is a current based process. Current fed to the battery results in
re-charging of the cells and consequent rise in battery voltage. Controlling the
current will control battery voltage. For 100% return of capacity, and for prevention
of excessive gassing and sulfation, the battery charging voltage is required to be
controlled at the specied Voltage Regulation Set Points for Absorption, Float and
Equalization Charging Stages for different battery types. Battery can, thus, be charged
at the specied Voltage Regulation Set Points by PWM of the charging current
through control of Duty Cycle as explained above. The controller checks the battery
voltage and updates the Duty Cycle regularly at a very fast rate. The Duty Cycle is
proportional to the difference between the sensed battery voltage and the Voltage
Regulation Set Point. Once the specied Voltage Regulation Set Point is reached, it
is kept steady - rise in voltage is compensated by reducing the average current by
reducing the Duty Cycle and fall in voltage is compensated by raising the average
current by raising the Duty Cycle. These fast updates on battery voltage measurements
and Duty Cycle corrections ensure charging of the battery at the specied Voltage
Regulation Set Point with minimum deviation of +/- 50mV.
Optimum PWM Frequency: The PWM frequency can range from tens of Hz to around
1000 Hz. At higher frequencies, the time period between the cycles is lesser and is not
sufcient to complete the electro-chemical reactions. At lower frequencies, the rise
times of the charging pulses are lower which results in higher gas bubble formation
resulting in lowering of active surface area and increase of internal impedance.
In SCC-30AB, frequency of 300 Hz is used for optimum charging performance.
Charging Algorithms
Notes:
1. For proper understanding of the charging algorithm, please read Section 3 –
General Information: Batteries.
2. For purposes of explanation given in Fig. 4.2A / 4.2B, it is assumed that there is no
load on the battery during the day when charging is taking place. There is small
lighting load at night, which is switched OFF during the day.

20 | SAMLEX AMERICA INC.
A
NIGHT
STAGE 1
BULK
STAGE 2
ABSORPTION
(1 HOUR)
STAGE 3
FLOAT
DAY
NIGHT
Va Vf
TIME
B
C D
EF
Fig. 4.1A - Normal Charging Algorithm Fig. 4.1B - Equalization Algorithm
BATTERY VOLTAGE
BATTERY VOLTAGE
NIGHT NIGHT
EQUALIZATION
(1/2/3 HOURS)
100% DUTY
CYCLE FLOAT
A1 B1
C1 D1
E1
F1
Ve
Vf
DAY
TIME
Fig. 4.1C LiFePO4 Charging Algorithm
NIGHT NIGHT
EQUALIZATION
(1/2/3 HOURS)
100% DUTY
CYCLE FLOAT
A1 B1
C1 D1
E1 F1
Ve
Vf
DAY
TIME
Fig. 4.2A. Normal Charging Algorithm Fig 4.2B. Equalization Algorithm
Following three types charging algorithms are used to ensure return of 100% capacity
and also to prevent excessive gassing:
•Lead Acid - Normal Charging (Fig 4.2A): This algorithm is used for normal day-
to-day charging. Charging is sequential: Stage 1: Bulk Stage (100% Duty Cycle
which is equivalent to Constant Current) Stage 2: Absorption Stage - constant
voltage charging for 1 hour Stage 3: Float Stage (Very low Duty Cycle of 0%
to < 10% which is equivalent to Constant Voltage).
•Lead Acid - Equalization Charging (Fig 4.2B): This is carried out automatically
after every 28 days or manually. Stage 1: Bulk Stage (100% Duty Cycle which
is equivalent to Constant Current) Stage 2: Equalization Stage - constant
voltage charging at the equalization voltage Stage 3: Float Stage (Very low
Duty Cycle of 0% to < 10% which is equivalent to Constant Voltage).
•Lithium Battery Charging (Fig 4.2A): This algorithm is used for normal day-
to-day charging of Lithium LiFePO4 batteries designed for lead acid drop in
replacements. Charging is sequential: Stage 1: Bulk Stage - Constant Current
output until voltage reaches Absorption voltage set point. Stage 2: Absorption
Stage - Constant voltage charging for 30 minutes. Stage 3: Float Stage -
Constant voltage charging.
Transition from one stage to the other will be controlled by the selected Voltage
Regulation Set Points as follows:
• Absorption Voltage Regulation Set Point “Va”
• Equalization Voltage Regulation Set Point “Ve”
• Float Regulation Voltage Set Point “Vf”
SECTION 4 | Principle of Operation & Features