OutBack Power RTS Remote Temperature Sensor Application Note

Application Note

Remote Temperature Sensor Communication

with OutBack Devices

Objective of the application note

Overview: This note will summarize the sharing of the Remote Temperature Sensor (RTS) data through

Outback’s communications network.

Scope/Introduction

The RTS provides temperature readings from the batteries to OutBack inverter/chargers and charge

controllers. The devices utilize those readings to adjust charging targets by linearly increasing the

voltage if the batteries are colder or decreasing the charging voltage if the batteries are hotter. In a

system with multiple inverter/chargers and charge controllers, they connect to a proprietary

communications network through a HUB so they can communicate for various reasons. One reason is to

share the RTS data among all the inverter/chargers and charge controllers. This is essential so all

devices can coordinate and properly charge a battery bank.

The RTS essentially is a 10k ohm resistor with a negative temperature coefficient. The internal

resistance changes inversely based on temperature. The inverter/chargers and charge controllers adjust

system charging voltage by –4 mV per cell per degree above 25° or 4 mV per cell per degree below 25°

Celsius based on the measured RTS resistance.

As an example: A 12-volt system has 6 cells in a battery and the room temperature being 8°C (–17°C

from the cross point of 25°C). It can be calculated as follow: 6 × –0.004 x –17 = 0.4 Vdc. The charger

will then compensate +0.4 Vdc above the target.

Inverter Only Systems

Although a HUB and MATE3 (or AXS Port) is required for stacking purposes, the FXR, Radian and “G”

series inverter/chargers have the ability to share the RTS data to all sub-phase masters and slaves on

their own. The “G” series inverter/chargers are pulse-width matched when charging or selling.

Therefore, with FXR, Radian and “G” series inverter/chargers only the master in Port 1 needs to have an

RTS. Classic off-grid FX models are the only inverters/charger series that cannot share the data among

themselves; therefore each FX will need their own RTS connected for proper temperature compensation.

Multiple Device Systems

Whenever devices such as charge controllers and a FLEXnet DC battery monitor are connected into a

HUB communications manager: A system display product such MATE, MATE3, or AXS Port is required

in order for the RTS values to be shared among all devices. Without the system display, the RTS value

is not shared between devices. This also applies to systems in which only charge controllers are present

and connected into a HUB product. The MATE or AXS Port will allow the RTS data to be shared among

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Application Note Remote Temperature Sensor Communication with OutBack Devices Objective of the application note Overview: This note will summarize the sharing of the Remote Temperature Sensor (RTS) data through Outback’s communications network. Scope/Introduction The RTS provides temperature readings from the batteries to OutBack inverter/chargers and charge controllers.
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Application Note all controllers when connected to the controller in Port 1. If no system display is present then each controller will require its own RTS. If a FLEXmax Extreme charge controller is employed in a system and is programmed to a temperature slope other than the default value, the RTS must be connected to it. The MATE or AXS Port will choose that RTS value and communicate it to all the inverters. The exception is the off-grid FX series, where only the master will respond to the external input.
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Application Note About OutBack Power Technologies OutBack Power Technologies is a leader in advanced energy conversion technology. OutBack products include true sine wave inverter/chargers, maximum power point tracking charge controllers, and system communication components, as well as circuit breakers, batteries, accessories, and assembled systems. Contact Information Address: Corporate Headquarters 17825 – 59th Avenue N.E. Suite B Arlington, WA 98223 USA Website: http://www.outbackpower.