Guide on How to Select a Solar Controller

The solar charge controller has a key role in the solar power system. The selection of a solar charge controller will affect the battery life. The main task of the solar controller is to properly charge the battery such that it lasts long. The controller will stop charging when the batteries are full. The controller avoids over and undercharging the batteries. Before answering the question “How to select a solar controller?”

Features of Charge controller:

A charge controller is a protection for the battery from over and under-changing. A solar charge controller must have the following features.

  • Disconnect the battery when fully charged.
  • Preventing undercharging of the batteries
  • Lighting load switching based on sunrise and fall
  • Status information of system users
  • Worked at wiring center
  • Direct Solar power to load in case of fully charged batteries.
guide on How to Select a Solar Controller

Types of Solar Charge Controller:

There are two types of charge controllers.

  1. Pulse Width Modulation (PWM)
  2. Maximum Power Point Tracking (MPPT)

MPPT or PWM Charge Controller:

The MPPT charge controller is more efficient than the PWM controller. The MPPT can deliver up to 30% more power than the PWM controller. MPPT allows low current and high voltage by connecting solar panels in series. The low current requires a lower wire size. Comparatively, the PWM charge controller is cheap.  A PWM controller is recommended if the solar panel output voltage is slightly higher than that of batteries.

Steps for how to Select a Solar Controller:

Voltage Selection

  • For making the calculation you need to know your load required.
  • After that, you may select the number of solar panels in the solar panel array.
  • Now know the voltage of your battery bank. It should be either 12V, 24V, or 48V because the controllers are offered according to these voltages.

Current Capacity

  • Now find the load current of a controller using ohm law like I=P/V.
  • Based on the amperage, select a slightly higher amperage controller.

Controller Selection Example:

For example, if you have a solar panel array with 3000watt power and 93.3 voltage DC. Where your battery bank is 48 volts DC then what controller should you use for the system?

Power = Voltages x Amperes

Amperes = Power / Voltages = 3000/48

Amperes = 62.5A

An extra 25% is left for future additions or extra bright conditions like sunny days or reflections from objects.

New amperage = 62.5 x 1.25 = 78.13 A

Now we must select a charge controller based on the 78.13A. The nearest controller is an 80-ampere charge controller.

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