Q72015

Hi All - Hope someone here can help. I have 3.0 ltr diesel Q7 2015 Reg. Post lockdown, I use my care rarely (once in 4 weeks or so) and I have been jump starting it every time I needed to use it after few weeks as you would imagine battery dies out within few weeks. Jump starting option worked couple of times but few days ago I tried to jump start as battery was dead again after 5 weeks, it couldn’t crank the engine fully hence engine didn’t fire up. I noticed smoke coming out of jump leads and when I checked the jump starter it was very hot too. Headlights of the car also started flickering like Christmas lights and after sometime pretty much all the warning lights came on. I disconnected the jump starter but noticed that in just one try, engine drained half of the charge from the jump starter. I did try to start with the key after that though to see if I can get rid of the warning lights but now even Key wouldn’t come out. I tried charging the battery and after 6 hours plugged in, battery charger started showing error light that it is not able to charge the battery. Now I am stuck in a limbo as I am not sure if I managed to fry my battery or did jump starting exercise fried car computer/electric. Wondering if anyone on this forum has had any experience like that or could help with what might be the issue? Many thanks in advance and much appreciate your help!