Jedi BMS circuit boards ordered
Above an impression of the finished PCB design for the main controller module. About half the board is taken by the ESP32 module with POE Ethernet port; the other half has two relays and an optocoupler to interface with the Remote Battery Switch, another relay to interface with the active balancer and a driver to send the sync pulses to the cell monitor boards.
There is a pin header for connecting a user interface PCB but I am not sure if I will even build that except maybe for initial testing. The ESP32 runs a webserver with a status page as well as a configuration page and also sends all data to a SignalK server like the Victron Cerbo GX.
The ESP32 module is rather high so for the rest of the PCB I could mount resistors vertical to save space. The rather empty area to the right of the ESP32 is to accommodate RJ11 jacks in the housing. The housing may even need to be larger than the PCB to mount all three of them: one for the cable to the cell monitor boards, the second to the active balancer and the third to the remote battery switch which is switched off when needed to protect the lithium cells.
Of course I also redesigned the cell monitor board, allowing a little more room for text at the connectors. The 8-pin J1 is for programming the microcontroller right under it while it is soldered onto the board, which uses the lower 6 pins. The two upper pins connect to the cell positive terminal and for normal operation a small jumper connects cell+ to vcc to power the board from the lithium cell. This jumper must be removed to be able to connect the 6-pin programming connector which then powers the board via the vcc pin.
I ordered the PCB's from JLPCB in China. The minimum order quantity is 5 so I get 5 main controller PCBs for €1.71. I need 8 cell monitor boards so I ordered 10 for €4.31 for a total of €6.02. Unfortunately Fedex shipping costs and duties and tax together costs a whopping €27.60 (4.5 times as much as the merchandise!) so the total is €33.62. I also checked for sending to my address in Florida and that was €11 extra, probably due to tariffs.
Next we will find out if my designs have been accepted for manufacture and then they will produce and ship them only two days from acceptance. Amazing service.
