Choosing a Location
The GP-MPPT-85/20 is designed to be mounted vertically. Allow at least 2in (5cm) of space around GP-MPPT-85/20 for cooling. Install on non-flammable surface. Do not install in direct sunlight.
The GP-MPPT-85/20 should be:
• Mounted as close to the battery as possible
• Mounted on a vertical surface to optimize cooling of the unit
• In an area with ventilation to dissipate hydrogen gas from batteries as well as heat from the controller
Choosing an Array
The panel voltage should not exceed 85V, or the controller will not charge the batteries. Panel voltage increases in cold weather compared to nameplate standard test condition (STC) ratings, so the highest panel array voltage must be calculated for the worst-case cold weather.
1. Determine the worst-case cold temperature of the panel installation.
2. Select the NEC temperature correction factor matching the worst-case cold temperature of the panel installation. Refer to table 690.7(A) of NEC 2017 or the latest version. When in doubt, select 1.25.
3. Sum the open circuit voltages (Voc) of panels wired in series to obtain the array open circuit voltage at standard test conditions (STC).
4. Multiply the array open circuit voltage by your selected NEC temperature correction factor, or multiply by 1.25 if you don’t know which factor to choose.
5. The calculated value must be less than 85V. If not, select a different wiring configuration for the solar panels with fewer in series.
For example, the FLEX-100 has a Voc of 20.8V at STC. If four FLEX-100 solar panels were wired in series, then the array Voc would be 83.2V at STC. If the array were to be used in temperatures down to -40°C, then the NEC temperature correction factor would be 1.25. Multiplying the array Voc by 1.25 is 104V. This is greater than the allowed 85V, and the panels must be wired in a different configuration.
NEC 690.8 defines maximum solar current as the sum of parallel connected PV module short circuit currents (Isc) at STC multiplied by 1.25. This should not exceed 25A. Equivalently, the sum of the short circuit currents before the NEC factor is applied should not exceed the controller nominal current of 20A.
Tools and Materials Needed
Philips Screwdriver (for mounting screws)
NOTE: If the GP-MPPT-85/20 Controller was purchased with a Go Power! RV Solar Power Kit then UV resistant wire is included. For instructions regarding the Go Power! RV Solar Power Kit installation, please refer to the Installation Guide provided with the Kit.
1. Complete the installation of the solar modules. If this GP-MPPT85/20 was purchased as part of a Go Power! Solar Power Kit, follow the Installation Guide provided. Otherwise, follow manufacturer’s instructions for solar module mounting and wiring. Keep the solar array covered with an opaque material until all wiring is complete.
2. Attach temperature sensor ring terminal to battery. Attach ring terminal to battery lug or use neoprene tape to attach ring terminal to battery case.
3. Mount the GP-MPPT-85/20. Mount GP-MPPT-85/20 to a nonflammable surface. Mount vertically for proper heat dissipation.
4. Select wire type and gauge. If this GP-MPPT-85/20 was purchased as part of a Go Power! Solar Power Kit, appropriate wire type, gauge and length is provided.
Wire type is recommended to be a stranded copper UV resistant wire. Wire fatigue and the likelihood of a loose connection are greatly reduced in stranded wire compared to solid wire. Wire gauge should be able to sustain rated current and minimize voltage drop.
IMPORTANT: All wiring must be in accordance to National Electrical Code, ANSI/NFPA 70.
IMPORTANT: Identify the polarity (positive and negative) on the cable used for the battery and solar module. Use colored wires or mark the wire ends with tags. Although the GP-MPPT-85/20 is protected, reverse polarity contact may damage the unit.
5. Complete battery wiring. Wire an appropriate fuse or breaker to the battery bank positive terminal. Wire the GP-MPPT-85/20 to the battery bank according to the wiring schematic in Section 6.0. Connect negative battery wire directly to the controller, not via the vehicle chassis. With battery power attached, the controller should power up and display LEDs.
Use of a positive or negative distribution bus is allowed between the controller and battery as long as it is properly sized, electrically safe and an adequate wire size is maintained.
IMPORTANT: Always use appropriate circuit protection on any conductor attached to a battery.
6. Complete solar wiring. Connect the solar wiring to the controller. Then remove the opaque material from the solar array. Connect negative solar array wire directly to the charge controller, not via the vehicle chassis.
Congratulations, your GP-MPPT-85/20 should now be operational. If the battery power is low and the solar array is producing power, your battery should begin to charge.
WARNING: This unit is not provided with a GFDI device. This charge controller must be used with an external GFDI device as required by Article 690 of the National Electric Code for the installation location.
WARNING: When the photovoltaic (solar) array is exposed to light, it supplies a dc voltage to this equipment
Products covered in this article: GP-MPPT-20, GP-MPPT-85