Ford Nugget LINBUS – part 7: Votronic MPPT 440 CI solar charger

The main purpose of examining the LIN bus in the Nugget is to develop a DIY monitoring device and website or app to be keep track of produced solar energy and the state of the batteries. The Votronic MPPT 440 CI has been selected as it supported the so-called CI-bus, which is more or less the same as a LIN bus, at least technically. And although being part 7, it is also the first device that got studied and decoded. A typical graph of Power, Current and Voltage looks like this:

On November 7th, it charged with around 100W. At this day the Nugget was parked in a sunnier location.

The Votronic answers to ID=0x20 on the LIN-bus. The first trace, Power is provided by the Votronics respons. The second and third trace, Current and Voltage are taken form the Hella IBS for reference purposes. The fourth trace is a status byte that I could partially decode. In the dark days and given de bad condition of the batteries, it will not get into the “float” condition so further decoding of the status has to wait until april or may. In those months charge currents above 15A are expected.

The “Power” value takes even 4 bytes of information. The calibration (x/47500) is provisional as charge currents are very low in the winter months. More importantly, it is unclear whether the bytes in the message represent a Power or a Current. Only with higher charge currents and more diverse battery charge states (read voltages during charging) this open question can be answered.

The same applies to the status bytes. In below protocol description some status bits in the byte are identified and the observed correlation or semantics is mentioned. However at least proper “float” conditions need to be observed before more certainty can be gained.

Votronic solar MPP regulator
ID  : 0x20
data: 6B 01 00 00 40
       |  |  |  |  |      
      PL PM PH PX  |           = Power (x / 47500) W - TBD Power or Current?
                  ST           = Charger status 0x40 = offline 
                   |             0x44 = bulk 0x5D = absorb 0x4D = bulk+absorb
                   |           = b0: 1 = high voltage when car engine running (14.7V)
                   |           = b2: 1 = online / or bulk, 0 = offline/sleep
                   |           = b3: 1 = absorb(1)
                   |           = b4: 1 = absorb(2) when car engine on, high voltage 
                   |           = b6: 1 (always)


Finally, I hoped to find also information on the MPPT tracking on the LIN bus. Or Voltage and Current at the solar panel side. This is not contained in the 0x20 message. It may be that the Votronic responds to more ID’s than the one requested by the touch screen. In view of the used ID’s in the Nugget, I don’t expect it. But it remains to be investigated.

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