Car won't turn over Need help troubleshooting
 

I have a 2005 S R53. I replaced the battery about a month ago. Car wouldn't even take a jump. It was dead at my job. Had a friend take me to get it tested. Battery was dead and I replaced. Now that I think about it this was precipitated by the gauge needles shaking a bit upon startup.

Now, I was about to drive to the store last night. Had the light on checking my list in the driveway for a minute. Turned it off, went to turn the key nothing. No click no try to turn over. Nothing. Silence. No headlights. When I checked the battery in the boot the light was very dim and it flickered. Up to this point no related issues albeit now that I think about it I do have to try a bit more than usual to turn it over.

So diagnostics insofar:
Battery charger said battery was at 75% No need for that. Battery is new and good. Charger confirms so not alternator or battery.

Checked the post/receptacle under the bonnet with a test light. Both had juice so this points to a bad connection. If it was the starter itself it would not affect the headlights.

Banged on starter. No change. Hoping it would make it try to turn over but not even a click.

The ground strap on the passenger side motor mount seems solid.

Also tried starting with the spare key. Nada.

Ideas? This car is the only car in the household and gets me to both jobs and back as well as supplies and meds for my parents whom I live with. So needless to say we depend on it for a lot. Thanks in advance.

It sounds like your battery is dead again. Not sure what that 75% means but if your dome light is super dim and the headlights dont go on I don't think your battery is charged.

I tend to concur. Get someone to give you a jump start or fully charge the new battery and, if that works, it would indicate that you have a drain on your electrical system.

you need a volt meter (DMM) , a test light is too crude to tell if you have 10 or 13 v.
I don't know what charger you have but the meters on them are usually about worthless.