Need new battery?
 

Hi I haven't started my car for months and it won't start even when I try to jump start it. At first it made fast clicking sounds, but after leaving the jumper cables and donor car on for 30 minutes, no clicking sounds anymore, now it makes half a cranking sound and goes dead. All the lights can be turned on. New battery needed? Also where is a good grounding spot in the engine? I clamped it to one of the hex bolts on the strut bar.

You need a new battery man. Pull it out and have it tested at the parts store to confirm it’s bad.

Get a Battery Tender, like the actual brand and one that charges AND also maintains that doesn't overcharge it while being plugged in for an extended period of time.

Depending on how depleted the battery is, the tender may be able to revive it. Also look at the battery condition. If it looks bloated, time for a new battery. For context, my Z is barely driven (I've put 12K miles over the past 7 years) and my battery is 5 years old. There was a time when my car didn't start due to the battery just sitting there, and bought a battery tender and was able to revive it. I leave the tender plugged in at all times.

In regards to a grounded location, I plug my tender to one of the bolts of the strut bar. It can be on the negative terminal post of the battery itself or any grounded metal point.

just change the battery if it is over 5 years old. the car does drain the battery over a few weeks time. mine usually drop down to about 12.3v after a couple of weeks

Another thing you can do if you don't have access to a nearby outlet like my parking garage is install a disconnect.
https://www.amazon.com/Battery-Disco...35179018&psc=1
You will have to reprogram the windows and clock also you will lose the maintenance intervals if you use that. With it I have gone over a month with no issues. You do have to run the car awhile till the alternator recharges the battery.

that is what I have. connect it every 2 weeks to top off the battery.

It depends on the driving habits. On my daily vehicles, I don't plug the battery tender on them at all. On my Z, I only take her out once every 2 weeks. The day after taking her out and after cooling down, I will attach the tender and leave it on until my next drive (I don't want to let the battery discharge too much in between).