If it's going to stay in the garage and you want it to also be good for coding then I'd do what I did this summer and get a RV power supply, at $126 it's crazy bang for buck. You buy a $14 6 gauge set of booster cables, cut them in half, and attach one half to it. I do have Battery Tenders 1/3/4 amps, and yes we're talking $126 + $14 v. $45....and portability.
https://www.amazon.com/WFCO-WF9855-W...s%2C166&sr=8-2
https://www.amazon.com/gp/product/B0...DL4H71TK&psc=1
The bang for buck isn't there on the 75A. You also need a 20A outlet, which I have, but the price delta wasn't there for me.
https://www.amazon.com/WFCO-WF9875-M...s%2C187&sr=8-2
I tested it to make sure it does what it says. When the car was off, with ignition on, the unit was providing 15A. When I turned on the headlights, 20A. These units are designed to power 12V appliances and to charge RV batteries simultaneously, and so the power is clean.
Why reinvent the wheel...
Someone here said the car draws about 15A when the ignition is on and I verified that.
this is headlights on
https://drive.google.com/file/d/17IC...w?usp=drivesdk
For me, I wanted to not drain the battery if I am doing something like ISTA-D
I never really got into the coding thing--I watched someone code the keys for my wife's GM and realized the interface is different. My take is it might fail or take forever otherwise (laptop communicating with car)...so I erred to the side of caution