You have a short or bad connection somewhere. Check the grounding wires and contacts on the battery, starter, relays, etc. If you have amp meter connect it to the battery + side and check if it is drawing any current when the quad is off. It shouldn't draw any or close to none. Now turn the ignition on and measure again. If the current stays high (few A for more than a minute) then start unplugging things to find the issue. Don't start the quad with amp meter connected since you'll fry it. Charge your battery.
2016 Raptor 700R, Street legal, HID kit, 15T front, AIS delete, Jogaca suspension, Adjustable rear link, LSR 2+1 A-Arms, Axcalibar axle, PC5 w/timing and autotune, full Dasa exhaust, Talon 36T rear or stock 38T