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Mini solar

charge controller

Fathima jahana

Shrimayi

Santhana lakshmi

ECE-B

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MINI SOLAR CHARGE CONTROLLER

Why a Charge Controller is necessary

Since the brighter the sunlight, the more voltage the solar cells produce, the excessive voltage

could damage the batteries. A charge controller is used to maintain the proper charging

voltage on the batteries. As the input voltage from thesolar arrayrises, the charge controller

regulates the charge to the batteries preventing any over charging.

Modern multi-stage charge controllers

Most quality charge controller units have what is known as a 3 stage charge cyclethat goes like this :

1) BULK: During the Bulk phase of the charge cycle, the voltage gradually

rises to the Bulk level (usually 14.4 to 14.6 volts) while the batteries draw

maximum current. When Bulk level voltage is reached the absorption stage

begins.

2)ABSORPTION: During this phase the voltage is maintained at Bulk

voltage level for a specified time (usually an hour) while the current

gradually tapers off as the batteries charge up.

3)FLOAT: After the absorption time passes the voltage is lowered to float

level (usually 13.4 to 13.7 volts) and the batteries draw a small

maintenance current until the next cycle.

The relationship between the current and the voltage during the 3 phases of the

charge cycle can be shown visually by the graph below.

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MPPT Maximum Power Point Tracking

Most multi-stage charge controllers are Pulse Width Modulation (PWM) types. I

would recommend using one of at least this design. The newer Maximum Power

Point Tracking (MPPT) controllers are even better. They match the output of the

solar panels to the battery voltage to insure maximum charge (amps). For example:

even though your solar panel is rated at 100 watts, you won't get the full 100 watts

unless the battery is at optimum voltage. The Power/Watts is always equal to Volts

times Amps or P=E*I (seeOhm's lawfor more info). With a regular charge

controller, if your batteries are low at say 12.4 volts, then your 100 watt solar panel

rated at 6 amps at 16.5 volts (6 amps times 16.5 volts = 100 watts) will only charge

at 6 amps times 12.4 volts or just 75 watts. You just lost 25% of your capacity! The

MPPT controller compensates for the lower battery voltage by delivering closer to 8

amps into the 12.4 volt battery maintaining the full power of the 100 watt solar

panel! 100 watts = 12.4 volts times 8 amps = 100 (P=E*I).

The Charge Controller is installed between the Solar Panel array and the Batteries

where it automatically maintains the charge on the batteries using the 3 stage charge

cycle just decribed. The Power Inverter can also charge the batteries if it is

connected to the AC utility grid or in the case of a stand alone system, your ownACGenerator.

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If you are using four 75 to 80 Watt solar panels, your charge controller should be

rated up to 40 amps. Even though the solar panels don't normally produce that

much current, there is an 'edge of cloud effect'. Due to this phenomenon I have

seen my four 6 amp panels (4*6=24) pump out over 32 amps. This is well over

their rated 24 amps maximum. A good 3 stage 40 amp Charge Controller will run

about $140 to $225 depending on features like LCD displays. For eight 75 to 80

watt solar panels you would need two 40 amp Charge Controllers to handle the

power or you could increase your system voltage to 24 volts and still use just one

40 amp Charge Controller.

PV :

Photovoltaic (PV) is a technology that converts sunlight directly into electricity. Itwas first observed in 1839 by the French scientist Becquerel who detected that

when light was directed onto one side of a simple battery cell, the current

generated could be increased. In the late 1950s, the space programme provided the

impetus for the development of crystalline silicon solar cells; the first commercial

production of PV modules for terrestrial applications began in 1953 with the

introduction of automated PV production plants.

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Figure 1: A photovoltaic panel being used in rural Nepal for solar lighting. Photo

credit: Practical Action.

Today, PV systems have an important use in areas remote from an electricity grid

where they provide power for water pumping, lighting, vaccine refrigeration,

electrified livestock fencing, telecommunications and many other applications.

However, with the global demand to reduce carbon dioxide emissions, PV

technology is also gaining popularity as a mainstream form of electricitygeneration.

Several million solar PV systems are currently in use worldwide, with an installed

capacity of over 6.6GW globally (2006), yet this number is a tiny proportion of thevast potential that exists for PV as an energy source.

Photovoltaic modules provide an independent, reliable electrical power source at

the point of use, making it particularly suited to remote locations. However, solar

PV is increasingly being used by homes and offices to provide electricity to replace

or supplement grid power, often in the form of solar PV roof tiles. The daylight

needed is free, but the cost of equipment can take many years before receiving any

payback. However, in remote areas where grid connection is expensive, PV can bethe most cost effective power source.

Solar PV systems

While in developed countries there has been a rapid increase in grid connected PV

systems, in developing countries the majority of PV systems are stand-alone off-

grid systems. The off-grid systems can be used to drive a load directly; water

pumping is a good example -water is pumped during the hours of sunlight and

stored for use; or a battery can be used to store power for use for lighting during

the evening. If a battery charging system is used then electronic control apparatus

will be needed to monitor the system. All the components other than the PV

module are referred to as the balance-of-system (BOS) components. The figure

below shows a typical configurations for an off-grid PV system. Such systems can

often be bought as kits and installed by semi-skilled labour.

For correct sizing of PV systems, the user needs to estimate the demand on the

system, as well as acquiring information about the solar insolation in the area

(approximations can be made if no data is readily available). It is normally

assumed that for each Wp of rated power the module should provide 0.85watt

hours of energy for each kWhm-2 per day of insolation (Hulscher 1994). Therefore

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if we consider a module rated at 200 Wp and the insolation for our site is 5 kWhm-

2 per day (typical value for tropical regions), then our system will produce 850Wh

per day (that is 200 x 0.85 x 5 = 850).

Some benefits of photovoltaics: No fuel requirements - In remote areas diesel or kerosene fuel supplies are erratic

and often very expensive. The recurrent costs of operating and maintaining PV

systems are small.

Modular design - A solar array comprises individual PV modules, which can be

connected to meet a particular demand.

Reliability of PV modules - This has been shown to be significantly higher than

that of diesel generators.

Easy to maintain - Operation and routine maintenance requirements are simple.

Long life - With no moving parts and all delicate surfaces protected, modules can

be expected to provide power for 15 years or more.

National economic benefits - Reliance on imported fuels such as coal and oil is

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reduced.

Environmentally benign - There is no pollution through the use of a PV system -

nor is there any heat or noise generated which could cause local discomfort. PV

systems bring great improvements in the domestic environment when they replace

other forms of lighting - kerosene lamps, for example.

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Solar Charge Controller

Features:

voltage regulation PWM shunt Battery charging floating charge automatic reconnection automatic selection of voltage (12V/24V) temperature compensation

Electronic Protections:

overloading protection short circuit protection reverse current protection reverse polarity protection lightning protection overcharge protection overdischarge protection

Technical Data at 25 :

Model CMP12-

6A

CMP12-

12A

Max. load current

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Few circuits

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