# CAN bus connections BMS charger and motor controller questions ?



## jacksdad (Apr 13, 2015)

Hi all 

for background please see my build thread in summary i am building an EV kit car with HPEVS ACx2 motor Calb batteries and Emus BMS and Elcon charger 

https://www.diyelectriccar.com/forums/showthread.php/electric-mev-rocket-kit-car-156145.html

I have just wired up the CAN bus connectors for the Emus control module and the 2 battery packs as per Emus directions. The charger from Elcon has a can module and as i think Emus supports Elcon chargers it makes sense to connect these together it is going to be an off board charger as at the moment my plan is to charge the car at home and drive it around then go back home and not charge off site. so i have a DSUB port for the can and will make up a wire to connect to the charger.

My question is - is there any good reason to connect the CAN bus for the BMS to the curtis controller CAN network that connects the two controllers together for my twin motor. I can't see that the BMS does anything very sophisticated with the motor controller apart from switch it off or put into limp mode if the voltage is low or other pack protection function. I guess it could be useful to controll the regen currents a bit like it controls the charger but i cant see any facility in the emus intructions for this - has anyone connected these together and how etc.

If the answer is that i should connect these together - there is a problem with this in that the CANbus for the controllers seems to have 2 terminating resistors - I assume these are at either controller - i can tell this because the resistance of the CAN bus when i connect the BMS CAN to the controller CAN is 40 ohms - i have one terminal resistor at the moment and so with 3 120 ohm terminal resistors this would give me the 40 ohms I think this will be too low when i add my final terminating resistor (30 ohm) and will affect the CAN signal and draw too much current from the devices i think. If i do connect then should i make the controllers a node and remove the terminal resistors or do i need to restructure the network somehow - any advice gratefully received.


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## jacksdad (Apr 13, 2015)

I have an answer to this from Emus for anyone else looking for this answer - their response was that as neither curtis or emus support each other they will not directly communicate over the CAN and therefore not worth connecting - they suggest that anaolog control is used to turn off the motor load in the specific protection situations eg over current over temperature low voltage etc so I will do this via a relay from the output pins on the interloc line on the controller to shut off if really bad and use the econo mode input on the curtis for low voltage or high temp control.

What they were not sure about is regen current - the limit for charging may batteries is stated at 1C so for my 2 in parallel this would 144 amps i have no idea if the motor could generate this kind of current or how to work this out and if there is a way to limit this - if anyone has done this please let me know ?


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## jacksdad (Apr 13, 2015)

Just got the elcon charger with CAN connector not a large amount of documentation and the CAN connector had none does anyone know which is CAN H and which is CAN-L for the can module:



I've asked evwest anyway but would be good to get idea


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## kennybobby (Aug 10, 2012)

Are the pins numbered--can't see them in your photo?

This factory-installed interface, allows ElCon PFC series chargers to communicate via CANbus. A suitable BMS can control the charger's output ramping charging current and voltage smoothly, avoiding inrush currents. This affords better care and more longevity to battery arrays.

If your ElCon charger was programmed as a standalone unit, it can be sent to the factory for re-programming with a CAN algorithm. 

Connects to the CANbus as follows:

Pin 1 to CAN-Lo

Pin 2 to CAN-Hi

If your BMS does not already have a 120 ohm termination resistor across CAN-Lo and CAN-Hi, you will need to add one

The charger expects to receive every second a message from the BMS with CAN ID 1806E5F4 and 8-byte data with the voltage and current requested. If the charger doesn't receive a valid CAN message in 5 seconds, it stops charging until it receives a valid CAN message. The charger sends out every second a CAN status message with voltage, current and status information. Up to 4 chargers with different CAN IDs 1806E5F4, 1806E7F4, 1806E8F4 and 1806E9F4 can be connected to the same CAN bus and be controlled by one BMS.

Compatible BMS controllers:

Emus

Orion

Elithion

EPS


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## jacksdad (Apr 13, 2015)

Hi Kennybobby

That is amazingly helpful thank you they are numbered 1 and 2 so thanks.

The elcon unit came from EVwest with CAN module and so i assume programmed to work with this. I have a CAN bus running through the car with nodes for both battery boxes can Modules, the BMS main unit and now the charger and 2 terminating resistors. 

Emus declare compatability with Elcon so I'm hoping i can choose my charger from the list in the Emus setup and all will work ! we will see.


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