When the key switch is turned on, current will flow through the resister and start charging the controller capacitors. Voltage across the controller will start at 0v and rise as the caps charge. When the voltage across the caps gets high enough, the relay will energize and bypass the precharge resistor. Turn off the key switch and the relay will de energize. This eliminates the need for a time delay relay, the R-C circuit is essentially a timer.
I have not tested this, and it assumes a few things: The relay can energize at less than the full battery voltage, since there will be a voltage drop across the resistor. and assumes the resistor is of a size to have enough current let through to both support the controllers current draw and the relays current draw.
I bought one of those big 50 amp anderson connectors and it's so big that I don't even see a spark. It was $8. I bought it at the local industrial supply store. I think the plastic is able to cover the spark.
You know I have never understood this sparking problem that some people have. Why would a controller spark when it's pluged in? Sparks are caused because a load is being drawn when the wires are connected. If you plug in a toster it doesn't spark. But if you have it activate (making toste) and you plug it in it will likely spark. The controller should act the same way. There is little to no load on the controller when you plug it in so it should never spark. I have 4 ebikes and none of them have ever sparked when pluged in or turned on. Just my opinion but I think it you are getting sparks when you plug in the controller there is something wrong.
My other e-bike sparks pretty bad. Not bad enough to really force me to change anything, though. My new bike has a on/off button on the controller so if I really wanted to, I could just plug it in while the controller is turned off.
The reason the controllers spark is the capacitors in the controller draw a large amount of current momentarily to charge up.
The problem with letting the spark happen is the arc leaves a carbon build up and can pit the contact surface. Over time it will ruin the connector or relay taking the spark. The cheap connector that came with my amped controller was already turning black around one of the pins.
Dude, if you have any ability at all with a razorblade and a soldering iron, you can do it. My kit came equiped with 30A Andersons, I bought a ton of pigtails, www.ebikes.ca sells them, so I built a Y-connector to set each 6S pack in series. You can easily add a fuse and On/Off switch.
I'ma go get the balancing connectors from an RC providor that has 20cm extensions, Clip one end and...