ON/OFF Switch to the controller

[Bikemad]

The key switches used on the GM battery contain very basic high current rotary switch contacts, with no form of electronic switching or precharge function.
Current limitation in this instance is only governed by the BMS's maximum current output, which is not low enough to prevent arcing at the switch contacts when the controller is first powered up.

A precharge resistor (or some form of solid state high current switching through suitable MOSFETs) is an easy way of preventing degradation of the switch contacts due to burning.

Fitting a precharge resistor (with battery voltage supplied via a momentary push switch) is a simply way of eliminating arcing at the switch.

Alan
 

[Sam.Vanratt]

Hi Alan
maybe I be of help here. The traditional way (apart from getting the function into the circuit design) is to bridge the contacts with capacitors in 100nF to 470nF which took over the function of taking the first current rush (inrush current) with no additional components needed. Old Relais were treated that way. More modern optical DC relays (called SolidStateRelais (bricks) could (due to their FET internal structure) implement a softstart, but are highly paid (one fitting for 50V/80A is the KS33/D-50D80-L which is compatible with Regeneration braking due to it's AC/DC capability). Would it be done in the Controller itself about 2EUR more would be sufficent instead of 20EUR as external part.
In high current switching typ. you (as designer) implement a softstart which limits the current and rise it over time (a few hundred ms are enough). That could be done (automatically) with one RCT (resistor-capacitor-transistor) with a "dead-man-switch" combination so it only consumes current when you triggered it.

Cheers
Sam

P.S.: Remember that with Regen enabled every switch must be reverse enabled with a fitting (schottky) diode so energy is not burned in the controller instead.

[Sam.Vanratt]

This would be a simple and quite easy to assemble SoftOn circuit with minimal losses:


P.S.: For Regen-Braking a schottky diode should be placed parallel to the FET internal free-wheeling diode to offload the high currents of Regen Braking. Double Bin Voltage as well (like NTST30100CTG =100V/30A).