Hello Doc,
I am a newbie about EV and I am trying to learn about charging. I have some questions.
If there is a BMS, isn't it opening and closing the contactor to modulate the charging current of the bulk charger
to effectively make it a smart charger? I was reading about BMS and couple of ways to control the balancing of the cells and
one way is to turn on/off the charger. The other way is to instruct the charger to go low current with CAM control or even analog signaling.
For sure there are more ways and I might got it wrong also .
Thanks for your help,
Giacomo
Hi
That's a good question and it deserve a good response!
Cheap Ebike ( electric bicycle ) chargers work that way, they trigger ON and OFF the charger to not overcharge and keep cell voltage below their limit, until all cells have reached their max voltage.. then current slow down to ideally C/20 with the CC-CV feature of the charger.
Some charger also have small current that will remain ON but that is under what the bleeding resistors current draw to help accelerating balancing state.
The BMS on electric car and the Zero are more complex and way smarter. They have very special algorithm that take account of the temperature, SOC, age and cycles of the battery to adjust current and enable or not. They even datalog all events in the processor memory.
The Contactor of the Zero drivetrain is not made to trigger ON and OFF at the rate a BMS would require to balance cells. Instead, The OEM Zero chager current is electronically controlled vis CANbus.
But if you BULK charge a Zero thru the controller DC connections or any other DC input the Zero have, it will remain protected against abnormal value and even if one or more limit( voltage, temp, current etc) is reached the contactor will open to cut the DC charging current input and keep the battery protected.
I suggest reading on the Zero unnofficial manual page to get more info.
Doc