Research

Over the last 15 years, a remote unheated off-grid cabin has been monitored using a variety of hardware and software solutions. The problems of limited sun and cold temperatures at the Alaska location have been solved using both custom and commercially available equipment.

A custom solution using a low power linux computer with a cellular module was developed by Serenity Lake Communications. This custom solution had the advantage of very low data consumption and very low power usage. For hourly monitoring of 50 data points, data consumption averaged 1/2 megabyte per month. A special mode using a sleep mode of the low power linux computer used 6 watts for a few seconds, 2.4 watts for 2 minutes each hour with near 0 watts for 58 minutes for an average consumption of 1/10th watt.

For extended industrial temperature ratings (-40°C to +85°C), the line of equipment from Morningstar Corporation is an excellent solution. Morningstar Corporation provides guidance for cellular or satellite connected monitoring of their equipment. The actual implementation of monitoring is left to the end user. Serenity Lake Communications has developed solutions for monitoring the Morningstar Corporation equipment as well as weather stations, cameras, heating systems and limited security systems.

Since our test location is in South Central Alaska, the extended industrial temperature ratings are sufficient. The following list describes various ratings:

• Full Military: −55 °C to 125 °C
• Automotive: −25 °C to 125 °C
• AEC-Q100 Level 2: −40 °C to 105 °C
• Extended Industrial: −40 °C to 85 °C
• Industrial: −20 °C to 85 °C

In Alaska, the low temperature range required for some locations go below the industrial ratings and some type of heat is required for power source. The test location is in an off-grid neighborhood. The full-time residents all use solar supplemented with lithium batteries and generators in a heated building. Testing in more extreme low temperature environments was not conducted.

Rechargeable Lithium batteries are not suitable for use in unheated locations. Lead-Acid batteries have limited power available at low temperatures; however, with proper management, they can be used down to temperatures below -40°C. In multiple year testing at temperatures down to -40°C, extended periods of low sunlight and low temperatures required reduction of loads to near zero. Each December with the exception of the very warm 2024-2025 winter, near the winter solstice, the system went into a low power shutdown mode until enough solar power to recharge batteries was available.

Ongoing research is focused on extremely low power and low data usage applications. Testing was conducted using several cellular modules using many protocols and services. The UDP transmission protocol was selected for minimum data usage. Data usage cost is in the $1.00 per year range using a specialized IoT data provider (1NCE.COM).

Our test location is in the Matanuska-Susitna Valley of Alaska where temperatures go slightly below -40°degrees C most winters. Commercial products from Victron Energy were also tested and functioned without failure.

Components Required To Monitor Morningstar Devices using Cellular Communications (reference Morningstar Corporation Product Connectivity Manual)

• Cellular Connection
  1. embedded module (NimbeLink, Quectel, Sierra Wireless, Telit), or
  2. USB modem (Huawei) and router (GL.iNet), or
  3. cellular modem-router (Sierra Wireless)
• Computer
  1. local with Modbus program and direct connection to cellular, or
  2. EMC-1 and VPN connection to cellular, or
  3. remote computer using MSView or other Modbus software and VPN connection to cellular
  4. Most Cellular and satellite internet connections require VPN to connect
  5. The MorningStar Ready Edge requires connection to internet for the SolarConnect web site (VPN not required for cellular or satellite connection)
• Connection to Morningstar device using
  1. USB (UMC-1), or
  2. RS-232 Serial (MSC), or
  3. EIA-485 Serial to RS-232 Serial (multiple devices) (RSC-1 and MSC), or
  4. Ethernet (TriStar MPPT charge controller), or
  5. EMC-1
  6. Ready Edge

Alternatives other than Morningstar devices tested:

The GlobalLink 520 monitoring device coupled with a Victron charge controller and Victron Smart Shunt battery monitor was a good solution for an unheated, low power installation in locations where temperatures seldom go below the rated temperature of -20°C (-4°F). In our test, the internal unit temperatures were high enough to continue working down to the extreme low of -40°C (-40°F) outside temperature. In addition to the solar power and battery monitoring, the unit was used to provide temperature from a RuuviTag and the single relay was used to supply power to a LTE Solar PTZ security camera with Lithium Polymer batteries. This arrangement allowed the security camera to function at temperatures below 0° C(+32°F) and prolonged darkness.

EXTENDED RESEARCH: Communications using cellular modules for monitoring of any data. The available cellular modules support many communication protocols including http, https, ssl, ftp, mqtt, sms, udp, coap, lwm2m and smtp (email). Actual availability of protocols varies with particular module. Power consumption can be extremely small when not actually transmitting data down to the picoAmp level. Cellular standards such as LTE-M, NB-IoT and LTE Cat 1 bis allow lower power consumption and lower hardware cost and are appropriate for low data usage applications.

Research has transitioned into sending monitoring data using many different protocols, devices and transmission standards to evaluate effectiveness. Hardware solutions have included small microprocessors and newer cellular modules that do not require a separate microprocessor.

SPECIAL CONSIDERATIONS: The most robust lower cost solutions are provided by companies located in China. The leading company, Quectel, is on the United States DOD 1260H restricted device list. As such, research is limited to applications that do not involve areas sensitive to United States national security.

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