To make it short, the reapir tool is very useless on big ships with like 1 mio hull. Can it get increased relative to the shipcore that i does like 1% of it ? But also disabled in a fight, else other would use it to cheat.
The repair tool isn't meant to repair big ships. How would one person with a welder repair a capital class ship in 100 seconds?
Your ship should repair it's hull automatically. From the entity mechanics (I believe you also have to enable plating for it to work):
Quote:Repairs health at the maximum of 5000 HP or 2.5% of max HP per second after not taking damage for 15 seconds. Requires energy supply.