Thanks for the response, and so sorry I didn't get back to you very fast.
To me it sounds like something is heating up and when warm has a lot of resistance.
High resistance in the battery cable or starter cable
Starter motor is weak and has high resistance when hot from the engine running
Poor connection that gets aggravated when warm (because things expand when hot)
To really find out whats going on. We'd need to do some testing.
Do you have access to a multi-meter (to measure the battery voltage) and a Clamp-on Meter that will measure current?
What we need to do is measure the battery voltage and current while you are cranking the engine over when its cold, and then repeat the same test once you've driven the car for 20 minutes. You may need a friend to help you with that one so you can watch the meters while your friend turns the key.
Would you be able to do that?
Friday, December 6th, 2019 AT 5:24 AM