Any mistake on your part in setting the charger, connecting the plug(s), or a problem with the pack thats not diagnosed and your plane, workshop, or immediate area are at risk of fire.
Best advice if your not sure, but even then its not good practice, is to remove your battery pack, any chemistry, and charge the pack out of the plane/vehicle. Its the safest way to ensure you know the packs condition and your able to respond to a problem immediately.
Best of all get a steel box like an ammo box, electrical junction box, or similar and modify it to be your charging bunker. Pass the wires through the wall and use a rubber grommet, thats it, and you will have a secure charging set up. Just be sure to allow some sort of exhaust port to let the pressure and hot gases to exit the box. Otherwise it can be dangerous as well.