If you leave for work at a consistent time, you could set the charger to end charging an hour _after_ you actually expect to leave. Then, when you unplug the car and drive off, it will be 1 hour short of full charge. (That said, if you're driving off right away, there's little harm in charging to 100%).
If you use the trickle charger, you could plug it into a timed outlet (which is rated for 15 amps), and program the outlet to power off 1 hour earlier than when the car is programmed to finish charging.
If you DIY home automation, there are relays which can disconnect 50A, driven by a Raspberry Pi, or similar. You could also connect at ammeter to a Pi and try to detect when the current draw starts to decline. But obviously, that's for pros.