Charging your batteries while still in the car and plugged into the esc is a very BAD idea for a couple of reasons and I will explain why.

1st, If you've ever witnessed or watched a video of a lipo fire, you would know that things can go pear shaped quicker then you would expect. With charging in the car you're at risk at damaging or destroying your car if something goes wrong and can't remove the battery in time.

2nd, Leaving the battery plugged in while charging could have serious consequences especially if you forget to turn it off, you could damage not only your esc, but also your receiver, servo, motor fan and personal transponder if you have one.

To charge my batteries I have a adapter like yours which is bullets to a female Deans plug, then I have a male Deans on the charger. I do this because that way I don't have 2 bullet connectors laying about from the charger output that could possibly touch each other and short out the charger.

In my car I use bullets soldered directly onto the ends of the positive & negative input wires of the esc.
One tip to do though is to make either the positive or negative wire shorter so it can just reach one side of the batteries terminals, and therefor can't be plugged in the wrong way if you're rushing or not concentrating at the time.

It's best off to be safe and remove the battery from the car when you wish to charge it and place it in a fire retardant container. A few extra seconds of time gained isn't worth risking losing your car, equipment or worse getting badly injured, play it safe.

Cheers
Rob