When things are clear, it takes 4 seconds to charge at a jumpgate. When enemies are near, this increases considerably. I believe it depends on how many enemies are nearby, but I've seen up to 3 minutes. That's a long time to be powerless and weaponless, just soaking up enemies fire!
This achievement is made much easier by a skill your Captain gets once they reach level 6 - Fast Jump Charge. Once earned, you can find the skill in the Captains menu, over on the right side in the Emergency panel.
To unlock the achievement, you obviously need enemies nearby. When you are close to a jumpgate, simply activate Fast Jump Charge. Notice that the Charge time on the left in the Hyperjump panel reduces considerably - as an example, I went from 2:39 to 0:20 on one jump.
You'll still need to hit the Charge button on the left to start the process. The Fast Jump Charge is on a timer, so don't get distracted!
Edit: You can also do this in reverse order. Start the Charge and then hit Fast Jump Charge to reduce the time.
Complete the jump as normal and the achievement unlocks as you reach the next area.