Sep
23
2014

EP Solar MPPT Tracer charge controller serial interface

I’m currently involved in a project to set up a solar powered wireless station and wanted to remotely monitor the battery charge process. I looked into a number of charge controllers to see if any of them could be connected to a computer. Many of the controllers have ethernet and built in web servers, but these come at a cost.

The (relatively) cheap chinese made EP Solar Tracer MPPT Solar charge controllers have an RJ45 interface for an MT5 remote display which means that there must be some way to get data out of the charge controller.

The MT5 remote display

The MT5 remote display



A couple of google searches for things like:

Brought up all sorts of documentation, much of the protocol information conflicted, but it all seemed to infer that the interface was serial of some sort.

I purchased the 40 Amp Tracer and borrowed a MT5 remote display and started snooping on the interface with a multimeter, oscilloscope and logic analyzer.

The EP Solar Tracer 40 Amp MPPT solar charge controller

The EP Solar Tracer 40 Amp MPPT solar charge controller

I was able to quickly verify the physical interface pin out.

Here’s the pin out of the RJ45 interface.

Pin1 +12V
Pin2 N.C
Pin3 +12V
Pin4 GND
Pin5 TXD
Pin6 RXD
Pin7 GND
Pin8 GND

WARNING: Pins 1 and 3 of the interface supply 12 volts DC. I’m unsure if these are fused, so be very careful not to short them to ground. Note that pin 4 is a ground, so it would be relatively easy to short pins 3 and 4 together.

Note: The wire gauge I'm testing with is far too thin for 40 Amp use!

Note: The wire gauge I’m testing with is far too thin for 40 Amp use!

The pin order is defined as: plug-oriented touch-sided view of the direction of the cable down, from left to right order of 1 to 8…. Or at least that’s how one of the translated Chinese documents describes the pin order.

Here’s a picture (courtesy of wikipedia) for clarication.

RG45 pin numbering (Wire colors are the TIA/EIA-568B standard)

RG45 pin numbering (Wire colors are the TIA/EIA-568B standard)

The serial interface runs at 9600/8-N-1 (9600 baud, 8 data bits, No parity bit and 1 stop bit) on 3.3 Volt TTL Logic.

A FTDI TTL-232R-3V3 USB to TTL serial adapter works well for testing purposes.

Connected upConnected up to a FTDI TTL-232R-3V3 USB to TTL serial adapter.  Wires on the left are from a TIA/EIA-568B cable plugged into the solar controller.  Inset box is the FTDI USB to serial pin out.

Connected up to a FTDI TTL-232R-3V3 USB to TTL serial adapter. Wires on the left are from a TIA/EIA-568B cable plugged into the solar controller. Inset box is the FTDI USB to serial pin out.

I want to interface the charge controller to a Raspberry Pi which is convenient as the RPi UART also works on 3.3Volt TTL logic levels.

I haven’t fully worked out the protocol yet.

The MT5 continually sends the packet

0xAA 0x55 0xAA 0x55 0xAA 0x55 0xEB 0x90 0xEB 0x90 0xEB 0x90 0x16 0xA0 0x00 0xB1 0xA7 0x7F

which loosely matches some of the documentation I’ve found online.

It looks like the response is a number of 16 bit integers (Least significant byte first) and 8 bit bool values. I’m still working on this and hope to have a result soon.

6 Comments »

  • Jiri

    Any news on reverse engineering the protocol? I have one next to raspberry also, although cannot access it in next 6 months (abandoned in island for winter).

    Comment | 7 November 2014
  • bart vanzetti

    HI,
    congratulations for your posted findings concernig this project!
    I’m pretty new with the RPi but I’m also trying to connect the rj.45 cable from the controller to a a RPi, not only to log it but also o access it remotely.
    have you made any progress?

    Comment | 7 November 2014
  • […] on from my previous post working out the EP Solar Tracer serial protocol, I’ve got code working on a Raspberry Pi. It’s even validating the CRC […]

    Pingback | 12 November 2014
  • Greg L

    Hi
    Working on a similar project with an Arduino as the remote monitor for the EPSolar MPPT. I used the site below as a reference. i’m also interested in a Pi solution.

    https://github.com/xxv/tracer
    https://github.com/xxv/tracer/blob/master/docs/Protocol-Tracer-MT-5.pdf

    Comment | 22 November 2014
  • murks

    Here is web page with much more information, including the protocol:
    http://blog.lekermeur.net/?p=2052

    Best
    murks

    Comment | 24 November 2014
  • phil

    great work guys!! I’ve just had one fitted to the boat and was told the remote wasn’t available but really wanted the rPi interface. Is there any info you can publish or is the above thread enough?

    Comment | 7 December 2015

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