Talk to an Angaran Mechanic in warehouse adjacent to the hangar in the northwestern part of the Resistance Base and he’ll freely hand over a schematic, which he claims will upgrade the Nomad’s shielding. To finish this simple task all you need to do is visit any Research Station and spend the necessary resources - 120 Iron, 40 Nickel and 30 Platinum (ouch!) to develop this "Improved Shield Regeneration" upgrade.
Warning!: If you buy this upgrade from another source before you get it here, you won’t be able to get rid of it from your crafting menu, and you may possibly not be able to complete this quest in unpatched versions of the game.