So I tried powering my little 48 VDC 10-20A electronic experiments and gadgets with a 48V LiFePO4 battery pack.
I initially got giant sparks when connecting the battery. I avoid the sparks by connecting a resistor in series, then manually bridging the resistor with a wire with some crimped-on connectors after a few seconds. That works, but it is of course rather cumbersome.
So I thought of building a simple relay circuit that would do this automatically.
Here’s the circuit:
Battery 48VDC (actually 55V) comes in. Inrush limiter resistor in series with the plus lead. Relay contact across the resistor. Relay contact rated 24V 60A. Relay coil with resistor in series, connected across supply after the limiter resistor. The relay coil resistor will be calculated such as to drop the voltage to the correct value (coil voltage and current TBD, but rather lower than the 48/55V supply). An electrolytic cap across the relay coil, calculated to give an appropriate relay closing delay, say 1 or 2 seconds. (I know how to calculate the resistors and caps.)
Would this be a good way to do it? Any tips? Improvements? Simpler ways to do it? Safety considerations? 50VDC won’t kill me but what are the risks of something blowing up?
Alternatively, is anybody aware of any ready made Chinese little gizmo on Amazon that I could use? So many great little Chinese gizmos on Amazon these days but I couldn’t find anything suited for this exact application.