Hello all...this is not technically an "EV" problem since it's for a boat battery bank...but here we go.
I'm in the middle of upgrading the AGM batteries on my boat to LiFePO4. The bank is 32 x 180Ah CALB cells in a 24V arrangement (4P8S)...but that's less important. I'm using an Emus BMS, and ordered the Elcon to support CAN charging.
Through some miscommunication with Elcon (that I'll take the blame for initially, though communication there has not always been 100%), what I wanted was two 3000W chargers in parallel. What I got was one massive 6000W charger 220V in, 24V out, with CAN. Other mistakes were made (like Elcon omitting the CAN dongle and any manuals from the original shipment, leading to confusion on where to connect the CAN bus), but the big delay is splitting the charger.
Several reasons for the split. The primary is that the double charger doesn't fit anywhere in the boat; it could not be installed safely in that configuration. Secondarily, I don't have any 220V circuits on the boat that can handle a 6000W load, so the source power needed to be split up.
From discussions with Elcon, I concluded the best thing to do was split the Master and Slave sides, get back plates made to mount these where I'd originally planned, and rewire them. Them being in the US and me being near Brisbane and already paying for marina space with my boat disabled in the middle of this project was a factor in not shipping it back to them, which could have taken a couple of weeks (waiting in a marina at rates for a 53-foot boat...).
As configured, the two chargers had one massive welding cable each for the positive and negative outputs. The cables were split at the base, with one half of each bundle being sent to a contact on each side of the charger, paralleling them together. (see picture)
There also was an AC input on the master that was wired to the slave.
My thinking is that taking each point where the output bundles go and making them outputs for each half would be the best way. So the + out and the - out from Master and slave are disconnected from the original cables, and new output cables are run from each source. Then, I could connect them in parallel outside the two boxes and have the same effect.
The slave also required a new A/C input (and to have the leads from the Master removed) and the CAN wire needed to be cut, extended, and reconnected.
Heres's the problem. I did all that. But when I turn the chargers on, charging kicks off...then the chargers start drawing massive load OUT of the batteries and the AC power connection to the Slave gets so hot it almost melts the wires.
Also of interest, when we completely disconnected the Slave, the Master would only put out about 1/3 of the current the BMS was requesting while making an odd high pitched whine.
Elcon suggested I might "have the slave wired backward" without telling me exactly what that might mean or providing any guidance on how to have these wired properly in the first place. That, and some finger wagging about how I should have shipped the 50Kg charger back to the US so they could rewire it... With instructions could do this in an hour or two instead of spending $$$ and weeks shipping it around the world and back, but I clearly screwed something up.
Anyone have any insights on how I screwed this up?
And how I can fix it?
By way of background on me, I've done a lot of 12V & 24V electrical work, but my electronics
experience is pretty weak in terms of practical applications. It's quite likely I've misjudged which end of this thing the power is coming into since the function of many of the lumps of mystery on the PCB alludes me.
Thanks in advance...