JK BMS GPS/UART Port GND Connected Directly To Battery Negative?

[bestconcreteblock]

It appears that the signal GND pin located at the GPS/UART port on JK BMS is not isolated from battery negative. This means a possible current path even with the mosfets turned off?

I am working on a controller that will communicate with the JK. It looks like I will need to isolate these signal grounds or I could run into issues with my controller drawing battery down even if mosfets are off.

These UART signals are 3.3V logic levels. The VCC available at this port is full battery voltage. It looks as though I will need a DC-DC to bring this down to 3.3V to be used with an isolator IC to bring signals to 3.3V level.

Any experience with this?

 

[SeaGal]

What power does your controller draw, what capacity are your batteries and how long will it be in a disconnected state?

 

[bestconcreteblock]

What power does your controller draw, what capacity are your batteries and how long will it be in a disconnected state?

Hmmm. Good point, maybe I am overthinking this... The controller and all the rest of the components(contactor, fan, etc) are powered from an Isolated 50W dc-dc converter. With this isolated, I shouldn't have issues I believe.

 

[SeaGal]

I have an ESP32 controller attached to my 14.3kWh pack - when I did the calcs it would be ages to discharge, so I just added a little toggle switch to disconnect it if, in the unlikely event, I needed to not use the pack for a few months.

 

[bestconcreteblock]

Almost talked myself out of it, but I am no longer isolated if this ground is connected... Battery could be disconnected from charger for medium long periods. Battery is only 60 Ah.

 

[SeaGal]

I have a long-term plan to take out my ground loop, but for different reasons - as detailed in this thread...

isolation of battery to inverter comms

I'm trying to get my head around how I've managed to blow a CANBus adapter (and fuse). Does anyone have experience of surge voltages may present on a battery to inverter CANBus link, when a battery is re-connected? In my case, I have a Solis hybrid (AIO) inverter, connected to my 14.3kWh...

diysolarforum.com

 

[bestconcreteblock]

I am planning on using a isolator like this:
https://www.digikey.com/en/products/detail/nve-corp-isolation-products/IL-712-2E/964106

I would need to power up the jk side of the isolator with 3.3V. For that I am thinking this:
https://www.digikey.com/en/products/detail/mornsun-america-llc/K78U03-500R3/16571471

Any thoughts on the VCC from the jk uart port being able to handle capacitor inrush from the dc-dc?

 

[SeaGal]

Sorry I have a JBD, no idea about the JK.