Soft start for a drone battery pack?

Question

I want to design drone landing pad that will automatically begin charging my drone as soon as it lands, I'm planning on having the drone legs have some pogo pins that will touch the pad it lands on which will have power through it. The issue I'm contemplating is that if the landing pad has a voltage from a cccv, I'm worried it will cause a large inrush current the second it lands on the pad. I wanted to attempt a soft start circuit, I have done some research and lots of typologies use quite a bit of components, I want to make it as simple as possible. Will a simple capacitor in parallel like this work? maybe even adding a Inrush current Limiter like an NTC Thermistor in series for current? Or am I thinking of this way incorrectly?

Also, for reference, the drone battery will need about ~16 V at 23 amps, I placed an 18 V source in LTspice for some voltage drops that will be in the system like a full wave rectifier for reverse polarity protection etc.. Last thing, I want the ramp up to be about 10 seconds till steady state

Answer 1

Will a simple capacitor in parallel like this work?

No, it will increase the surge current.

You have made two mistakes in the simulation:-

1. If the the drone is not connected when the cccv charger is powered up, it will charge the capacitor to full voltage. You should put a switch in the simulation representing the connection to the drone.

2. When the drone lands and makes contact, the capacitor will discharge into it with no current limiting. The battery pack should be modeled as a voltage with a small resistance in series.

A better scheme would not turn the charger on until detecting that the drone is connected, eg. by monitoring the voltage on the pins, or via a microswitch or other proximity sensor. How to ramp the current up slowly when the charger is turned on depends on the circuit used, but it would probably involve a smaller capacitor in the current regulating loop.

the drone battery will need about ~16 V at 23 amps, I placed an 18 V source in LTspice for some voltage drops that will be in the system like a full wave rectifier for reverse polarity protection etc.

I fear you do not understand the requirements for safe charging and operation of lithium batteries. 23 A is a lot of current, suggesting a very large battery pack and/or high charging rate. The voltage needs to be precisely limited, and some protection against charger malfunction included. Cell balance should monitored and the charger cut off if any cell goes too high. Large drones can be lethal too. 'As simple as possible' is not good if it compromises safety.