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The picture is not clear enough to read the printing on the boards or trace the wiring, but it looks like you have 4 1.5kW chargers ganged together. So i'm thinking that there would be one master and 3 slave units to make up the 6kW unit. And if you want to split them, then one of the slaves must be configured into another master.
They look like the older boards for which we have schematics, http://www.diyelectriccar.com/forums/showthread.php?t=89470,

But our resident expert on these chargers is "Coulomb" from Brisbane, and he has more experience with those big monster chargers. Which marina are you located?

If you wired up the slave outputs backwards, i.e. with reversed polarity, then when the output relays were commanded closed by the master, the slaves would be drawing power from the cells thru the inductors and the final stage rectifier diodes.

The AC wires to the slave getting hot seems to be an overcurrent condition, such as the diode bridge is shorted, but there is a fuse on the mains that should blow.

One thing i noticed is no green ground wire running to the 4th unit to the far right in the photo? For that matter, why are the grounds not connected to the input AC Ground wire and why is that wire so tiny--it should be the same size as the input at least?

Is the photo the "before" picture of how it was rec'd from the vendor, or is it showing wiring changes that you made?

How/where are you getting your 240vac--is it a generator on board, or do you connect a land line to the mains?

Nice looking boat, funny blog: could you not use the B-word for one hour...
 

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i hope you guys can get together and figure out this mystery. i went to see Paul yesterday and we puzzled over this but couldn't resolve what it was doing--why it should load the battery or why it should pull excessive mains current to heat the wires.

We opened a 3kW unit and found that they don't run the mains ground wire to the slaves, so that may not be related to this issue, although it is a poor practice.

Some pictures might help for sure. On the 7-pin header, the red wire is ground pin 2, and the black wire is the Slave Rx line pin 6 in this 3kW charger.


 

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It appears that it's all connected properly.

One odd thing i noticed is that there are no output fuses on the Positive Outputs on any
of the boards--usually there is a fuse soldered onto the boards right next to the B+ terminal...?

Which AC wire was getting hot? None of the Red AC terminal lugs are touching the housing right?

Can you hold back the white plastic on the master upper right hand corner and get a photo to show
where the small red and black serial port wires are connected--is there a separate little circuit board
such as seen on the slaves or is there a header connector?

Do you have a CAN dongle from Elcon thru which it routes the CAN messages to the charger
and does it connect to the 7-pin round DIN connector with the blue cap? i assume that is the
case but wanted to check. The Master sends commands to the slaves over the serial port.

Does the small red serial line from the master route to the green wires (pin 6) going to the slaves?

In the Slave unit one board uses a yellow wire for the ground pin 2, the other looks like it
uses a black wire. In the Master unit it appears that green is the serial line and black is the
ground going to the slave board.

Those serial port grounds are also connected in common with the battery negative terminals,
so polarity is important.
 

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Good onya Mike.

That bare control board without the black coating sure would have made our past efforts easier--but if ever there were boards that needed coating, or should have had the coating, it would surely be on an ocean-going BOAT.

i'm trying to understand how the green/yellow wire could get hot enough to melt insulation or a blob of the yellow gunk on the AC capacitor near the input fuse. Is that what was smelling of heated or burnt plastic? i don't see scorching in any pictures.
 

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How about a cover screw right above the Red +ve welding cable gland nut--maybe screw is cutting
into the cable and shorting to chassis?

Have you narrowed it down to the Slave pair?

Pull the cable and inspect underneath these marked areas--maybe the sharp edges have cut into the cable and short when
the cover presses on it. i would try to re-route it, it's too big anyway considering the size of the jumper wires.

 

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Good catch on the overvoltage, that will damage cells. The damage manifest as swollen cells that won't hold a charge.

That's what initially got me involved in reverse engineering these chargers, Paul had a cell in his Celica pack get damaged by the over charging and wanted to figure out how to change the voltage.

From subsequent research and testing we found that the resting voltage of a full cell is only 3.33 volts. There is no useful meaningful energy above that point as the voltage will drop immediately to that level when loaded. The risk of damage by charging to a higher voltage is not worth it.
 
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