My wife had a dead battery

Actually, her 1995 Mercedes SL320 'toy car' that she bought last year had a dead battery... it was SO dead that my battery charger would not work (which I read about after doing a search) so I had to use jumper cables AND run our other car at about 2500 RPM for 20 or so minutes to get her battery to charge enough that the starter would work... at which time my charger would work overnight to finish charging the battery

When you have a 'Garage Queen' car that is not driven often, you need to have a trickle charger attached to the battery or you run the risk of having the battery go DEAD due to the usual 'stuff' that draws power even when sitting... so, I just added one to my wife's car that is never driven when it is raining

https://www.amazon.com/MOTOPOWER-MP00205A-Automatic-Battery-Maintainer/dp/B06XWDZ2KQ/