Controlling the Cotek inverter in my power management system.

I am building Power management system with a GSMCommander controller for my house.
1) I need to Control my Cotek SK1500 inverter remotely so that I could disable the unit when the batteries go below a 11V level.
Although the internal configuration of the inverter will disable the the output of the Inverter it is at a to low level plus minus 10V.
If I disable it at 11V I could get about double the life cycle out of the Batteries. The remote interface on to the Cotek inverter also allow me to monitor how much power I do have left for the Day and I can then switch things off in the house as required.

2) Communication with Cotek is via RS232 interface 4800 Board.
3) Need to install Isolation relay to switch to City power automatically when Inverter is switched off with remote control.
I Will show you a picture of the Isolator rely next time I open the enclosure.
4) Cotek 6 Pin Phone Jack

4.1) Pin 1 N/C
4.2) Pin 2 GND
4.3) Pin 3 RXD
4.4) Pin 4 TXD
4.5) Pin 5 Vcc
4.6) Pin 6 N/C

5) Protocol.
5.1) 12 Bytes long
5.2) String Termination (CR )(HEX 0DH) and (LF) (HEX 0AH)
5.3.1) Respons String =>CRLF (OK)
5.3.2) Respons String ?>CRLF (Error)
5.3.3) Respons String !>CRLF (Comand OK Value out of Range)

6) Commands.
6.1) Power saving Commands.
6.1.1) PWRS[]<0,1,2>CRLF <> = value of 0 ,1 or 2
[] = space (HEX 20h) <"0" or "1" or "2"> 0=Disable 1=Enable 2=Inquire

6.2) Power ON / OFF Commands.
6.2.1) POWER[]<0,1,2 or 3>CRLF
[] = space (HEX 20h) <"0" or "1" or "2"> 0=OFF 1=ON no wake up 2=ON 3= Inquire

6.3) Status Commands.
6.3.1)STUS? ?= ASCII code between 00 to FF
"B0" UVP
"B1" OVP
"B2" OLP > 110%
"B3" FLP > 100%
"B4" OTP
"B5" Batt Low
"B6" Batt High
"B7" Load High

6.4) Battery Voltage Commands
6.4.1)BATT?CRLF
Read Battery Voltage
Hex DEC 12V 24V 48V
"00" 0 <10.6 V <21.2V <42.4 V
"01" 1 >10.6 V >21.2V >42.4 V
"02" 2 >11.0 V >22.0 V > 44.0 V
"03" 3 >11.4 V >22.8 V > 45.6 V
"04" 4 >12.0 V >24.0 V > 48.0 V
"05" 5 >12.4 V >24.8 V > 49.6 V
"06" 6 >12.8 V >25.6 V > 51.2 V
"07" 7 >13.2 V >26.4 V > 52.8 V
"08" 8 >13.9 V >27.8 V > 55.6 V
"09" 9 >14.3 V >28.6 V > 57.2 V
"0A" 10 >14.6 V >29.2 V > 58.4 V
"0B" 11 >14.9 V >29.8 V > 59.6 V

6.5) Power Load Commands.
6.5.1) LOADCRLF
Read Load Level
HEX DEC Load status
"00" 0 < 5%
"01" 1 < 15%
"02" 2 < 25%
"03" 3 < 35%
"04" 4 < 45%
"05" 5 < 55%
"06" 6 < 65%
"07" 7 < 75%
"08" 8 < 85%
"09" 9 < 95%
"0A" 10 < 105%
"0B" 11 > 105%

I planning to use the GsmCommander to control the Cotek inverter.

Here is my details and will list program when complete.

Note: I found it difficult to get Communication details for the Cotek on the web but eventually got the details from Cotek support.

ref http://www.canadianpowerconversion.com/files//sd%20series%20manual%20(2013).pdf