If you have used those cheap battery cable ends to repair the old cables, you'll also want to totally disassemble those, too. Hidden corrosion can usually be found inside the little clamps that connect to the cables.

If you clean everything up and then find the cable ends feel loose in the fittings, reverse the 'bridge' part of the clamp so it's dished in over the cable end, instead of humping up. This will give you better connection for a while.

If you have any type of cobbled together cable ends, plan on replacing the cables very soon. Having poor connections to the battery puts a lot of stress on the charging system, and can lead to expensive repairs later on.

Better to spend a few dollars now rather than a lot of dollars later on!

The most likely place for your current problem is with the cable ends and battery terminals. Corrosion can build up in hidden areas, and the result is exactly the problems you're describing.

A good cleaning with baking soda and water paste, and after the problem is solved, a good spray with battery terminal sealer will go a long ways towards keeping this from happening again.

Part of my regular 'oil and filter change' routine includes a good cleaning of those pesky terminals.

Good luck!

Steve