Tag Archives: Maximum Power Point Tracking or MPPT Charge Controllers

Solar Panel Charge Controller

31 Jul

Charge controller is used to charge batteries from Solar Panels. Solar panels normal give 15-17 volt, charge controller converts that to 12-14 volt and charges battery. Battery often needs a higher voltage than it already has to charge the battery. Most multistage charge controllers are Pulse Width Modulation (PWM) types. Maximum Power Point Tracking (MPPT) controllers are new and much better; these controllers match the output of the solar panels to the battery voltage to ensure maximum charge (amps).

Benefits of Solar Panel Charge Controller

·         Charge controller prevents batteries from being over charged, it will give longer life for battery.

·         The excessive voltage could damage the batteries. A charge controller is used to maintain the proper charging voltage on the batteries.       

Stages of Charge Cycle

1.    Bulk Phase. 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 Stage. 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 Stage. 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.

Types of Solar Panel Charge Controllers

1.   Maximum Power Point Tracking or MPPT Charge Controllers

MPPT stands for Maximum Power Point Tracking. MPPT is an electronic method of capturing the most power from your PV solar modules. MPPT controllers will convert the module operating voltage to battery voltage and raise the output current (amperage or amps) in the process. Convert a higher voltage DC output from solar panels down to the lower voltage needed to charge batteries. Most modern MPPT’s are around 93-97% efficient in the conversion. When you connect 150 Watt Solar Panel to your battery through a regular charge controller, your battery is at 12 volts. A MPPT takes that 17.6 volts at 8.5 Amps and converts it down, so that what the battery gets is now 12.5 Amps at 12 volts. Now you still have almost 150 watts. Actually the output of the MPPT charge controller might vary continually to adjust for getting the maximum amps into the battery.

2.   Pulse Width Modulation (PWM) Type Charge Controllers

PWM solar chargers use technology similar to other modern high quality battery chargers. When a battery voltage reaches the regulation set point, the PWM algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet the charging continues to return the maximum amount of energy to the battery in the shortest time. The result is a higher charging efficiency, rapid recharging, and a healthy battery at full capacity.

3.   Most suitable Conditions for Using MPPT Charge Controllers

MPPT’s are most effective in winter and cloudy or hazy days, when the extra power is needed the most. The MPPT work most efficiently under these conditions:

·   Cold Weather. Solar panels work better at cold temperatures, but without a MPPT you are losing most of that. Cold weather is most likely in winter – the time when sun hours are low and you need the power to recharge batteries the most.

·   Low Battery Charge. The lower the state of charge in your battery, the more current a MPPT puts into it. You can have both of these conditions at the same time.

·   Long Wire Runs. If you are charging a 12 volt battery, and your panels are 100 feet away, the voltage drop and power loss can be considerable unless you use very large wire.

4.   Selection of Solar Panel Charge Controller

 

Solar charge controllers are rated and sized by the solar panel or array current and system Voltage. Most common are 12, 24, and 48 volt controllers. Amperage ratings normally run from 1 amp to 80 Amps, voltages from 6-60 volts. For example, if one module in your 12-volt system produces 7.45 amps and two modules are utilized, your system will produce 14.9 amps of current at 12 volts. Due to light reflection and the edge of cloud effect, from time to time increased current levels are not unusual. For this reason we increase the controller amperage by a minimum of 25% bringing our minimum controller amperage to 18.6. Looking through the products we find a 20-amp controller, as close a match as possible. There is no problem going with a 30-amp or larger controller, other than the additional cost.

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