MX32FU charger


OK, my new MX32FU super gee whiz cabs are rechargeable, and the batteries are locked inside.

To charge them, you connect them to the Zimo CAN bus jacks, one on front and one on back.

I knew that since the unit is outside in a weatherproof enclosure, I would need a way to charge them not connected to the MX10.

The more I looked at the jacks, the more confused I became.

First the jacks are RJ45 (8 position), but you use the CAN BUS cables supplied, which are 6 position.

On the front, it's the left hand jack



On the back, it is the left hand one again.


Figuring out the wiring


I figured the first place to start was the CAN bus standard:

  1. CAN high
  2. CAN low
  3. CAN ground
  4. reserved
  5. reserved
  6. CAN shield
  7. CAN ground
  8. CAN V+ (optional power)

Zimo's "CAN" bus socket pinouts

But to add to the fun, there are labels on the MX10 front to identify the pinout:

Please note that the jacks have pins numbered from 1 to 8 left to right, when the locking tab is down.

So from the front panel we have:

  • snif +
  • snif -
  • ground
  • CAN H
  • CAN L
  • ground
  • + 30v

Notice that there are only 7 pins listed of the 8!!

Now looking at the back, we have 8 descriptions (better!)

  1. Boo N (booster N)
  2. Boo P (booster P)
  3. ground
  4. CAN H
  5. CAN L
  6. ground
  7. + 30v
  8. Boo UE

OK now this is making a bit of sense..

If you plug a 6 pin into the center of the above units, you get

  1. snif - or Booster P (which the cab probably ignores
  2. ground
  3. CAN H
  4. CAN L
  5. ground
  6. +30v

I measured the voltage and found 31.95 volts between pin 5 (-) and pin 6 (+) of an RJ12 cable plugged into the rj45 socket (note the pins refer to RJ11/12 NOT the RJ45 1-8)

Now, I still wanted to validate the Zimo CAN bus from a document. Axel Tillman sent me this:

zimo can

 This was for the MX1, but you can see the wiring order is right, except the pin numbering is backwards. If you number the pins according to standards:


Then everything matches.



The simple method was to take 2 RJ-11 plugs and only crimp 2 wires into them, positions 5 and 6. Remember the definition above for pin numbering, not the pin numbers in the picture of the Zimo cable.

So with wires in only positions 5 and 6, and I used a red wire in position 6 to remember polarity. It might be good to put a diode in series with one of the wires to protect from reverse polarity. If you add a diode, make sure you subtract 0.7 volts from the supply voltage (this is why I have picked 9 volts for supply).

After a while, both cabs throttled down to about 0.18 amps, so the charging system is working fine. I do detect more heat from the cabs when charging at 30 volts.

I have experimented with lower voltages, and there's no heating, and no appreciable difference in charging speed. I have picked 8-9 volts.

The way I detect full charge is that the voltage in the cab no longer increases:

Cab 1 finished at 4127 millivolts

Cab 2 finished at 4175 millivolts

I would like to see what current draw would be when the cabs are off, but they cannot be off when power is applied.

A tip, if you plug the cab in and it boots but not completely, unplug it and plug it back in.


Weather Underground PWS KCACARLS78