So in-game, I have zero shield recharge delay. As soon as I stop getting shot, it's filling up. There is no perceptible delay between "decreasing" and "increasing". And I can easily perceive a delay of 100ms.
But I can't quite figure out the math on this. Krestel Helm: +10% Kassa BP: +10% Defense Matrix: +15% Fitness: +15% ... so that's +50% by myself
Javik: Vengeful Ancient: +20% Kaidan: Alliance Officer: +15% ... total of +85% with squadmates
There are no upgrades (from the terminal in Liara's quarters) that affect shield recharge delay.
The base shield recharge speed is what, 3 seconds? So 15% of that is 450ms. And it's certainly not a half-second.
If the effects were multiplicative, it would be 1.2 seconds or something. So that's not it.