How do I disable the second fan?

I've tracked Commissioner Gordon to the mall. I've opened the door and taken out the first round of goons with the Batmobile's, disabled the first ventilation fan, taken out the second set of goons across the ventilation shaft.

Now I find myself riding the elevator up and down looking for a way to the second power source under the second fan. I've tried shooting the fan's power source with the REC gun through the fan with no success. I've tried using the explosive gel to destroy the weak wall at the bottom of the elevator, but Batman just shakes his head at me in disgust.

Where do I go from here to disable the second fan?

Solution 1:

There are spinning generators behind the walls that you have to overload with an electrical charge to turn off the fans. To access the generators, you have to lower yourself in the Batmobile into the shaft as far as you can go. There should be a shootable wall nearby that you have to shoot and go through. Exploring the opened area should eventually lead to a generator that you have to overload with an electrical charge. It may seem like a dead end but look around, there are shafts and whatnot that you need to go up or down to get to the generators.

Here's a playthrough that's going through that section. (it begins at around 5 minutes into the video)

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