the tank has a giant gas turbine why do you need a battery

The battery isn’t the issue they were talking about. They meant “so instead of batteries on the quad you’re powering it from the tank.”

The battery is there so you can actually use the 5kW laser at peak power. Even if you somehow make a tank with a 5kW turbine you don’t want to divert all power away from it to a drone that may or may not fry optic fibre cables around you, even if it’s only firing for a few seconds at a time

The gas turbine in an Abrams produces 1100 kW

en.wikipedia.org/wiki/Avco-Lycoming_AGT1500

If you mean a dedicated turbine producing 5kW of electricity then it already has an accessory gearbox drawing up to 75kW out of the 1100 for peripherals. I doubt they’re currently generating (pun intended) huge amounts of electricity, but the drive is there for exactly this sort of purpose.

A 5kW alternator seems to be about $700 on ebay

www.ebay.com/itm/146849456677

If a reasonably skilled engineer cant fit that there’s something wrong