Info

Temperature difference between STC & record low = 25°C - (-29°C) = 54°C

Use the module's temperature coefficient specification to find the Voc increase at record low temperature = 54°C x 0.12 V/°C = 6.48 V

Voc/module at record low temperature = 33.2 V + 6.48 V = 39.68 V

2. Find the maximum number of modules that can be used in series based on the example controller's 150 V maximum Voc.

Two series modules: Voc = 39.68 V x 2 = 79.36 V = OK Three series modules: Voc = 39.68 V x 3 = 119.04 V = OK Four series modules: Voc = 39.68 V x 4 = 158.72 V = Too high! Three modules in series is the maximum.

3. Find the number of controllers required and the number of module series strings per controller.

4,920 W (array peak size) + 46 V (min. battery voltage anticipated) = 107 A

107 A (total max. output current required from MPPT controllers) + 60 A (output per controller) = 1.8 controllers. Two 60 A controllers are needed.

For our total of eight series strings (24 modules at 3 modules per series string = 8 strings), put four strings on each of two 60 A charge controllers. Each charge controller will be wired to 12 modules (4 strings x 3 modules per string).

The Specs—Using This Guide

Nominal Battery Voltages—The nominal, or "name plate" voltage of a battery bank depends on the nominal voltage of the individual batteries and how they are wired together. Most residential-scale battery banks are 12, 24, or 48 volts, with 24 and 48 V most common. Some less common battery banks are 36, 60, or, rarely, 120 V nominal. Many newer charge controllers can be field-adjusted to accommodate any of several different battery bank voltages.

Rated Output Current—This is the maximum amperage the charge controller is designed to put out continuously at the rated operating temperature. Above these temperatures, the output will decrease and energy will be wasted. These temperatures may seem high for most climates, but the charge controllers and other associated equipment also produce heat during operation.

Xantrex's C60 charge controller.

Xantrex's C60 charge controller.

Charge Controllers & Specifications

Array-to- Built-In

Maximum Battery Step- Battery Terminals'

Nominal Rated Output PV Open- Down Option State-of- Wire Size

Battery Current Circuit (Max Voc to Charge Range

Manufacturer Model Voltages (V) (Amps @ °C) Voltage (V) MPPT Nominal V) Meter (AWG)

Array-to- Built-In

Maximum Battery Step- Battery Terminals'

Nominal Rated Output PV Open- Down Option State-of- Wire Size

Battery Current Circuit (Max Voc to Charge Range

Manufacturer Model Voltages (V) (Amps @ °C) Voltage (V) MPPT Nominal V) Meter (AWG)

Apollo Solar

www.apollo-solar.net

T80 TurboCharger

12, 24, 36, 48

80 A @ 45°C

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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