Switch ON OFF ESC relay capacitor precharge


#1

I want to show a new approach to switch on/off an (V)ESC with a simple manual switch, a relay and a resistor.
For Efoils we developed some circuits to (de)power.
I for myself tried different circuits, misusing BMS e.g.
I now use an Albright, which has a single throw, normally off. http://www.albrightinternational.com/wpcms/wp-content/uploads/2017/04/SW60P-Catalogue-Data-Sheet.pdf
I used to use a DMS which is closed, when you apply the key. I used the Lanyard once and never again. It only poses risk, the restrictment in movement is too much and the binding between the transceivers is always lost. After some time, the DMS died, because it is not really watertight, but only in the advertisement.
Now i built in a simple waterproof switch, http://www.itwswitches.com/S76-97.shtml
I use the NO and want to switch on my VESC with high quality Elkos and other caps which would pose a very high inrush current through the Albright into all capacitors. I want to avoid an extreme inrush current, on the other hand i want it to be fast.
I read the datasheets, and the reaction time of such relay is around 15ms.

The switch is triggering two functions at once:

  1. preload the capacitors immediately by a resistor and a transistor (NMOS FET).
  2. with a delay of 10-20ms after the first contact for the precharging, the relay will engage fully and finish the charge and take over all current because it has thousandwise lower resistance.
    By this the inrush current is limited in peak to 50A instead of 400A. Albright, Battery, ESC Caps and everything is treated nicely.
    Here is a simulation with ltspice:

The measurement with oszi looks similar.
What do you think? Is this a suitable way to use the delay of the relay to precharge or is it still much too fast? Which part would suffer from the remaining inrush currents? Are the capacitors fine with 30-50A inrush?
I tried 2 and 3 4.7ohm resistors in parallel, Oszi signal is very weak now, i am looking at the 1mohm shunt and it shows 25-35mV, = 25-35A peak current. No swinging when the relay contacts close.