Fernando the electronics guy is an electronics engineer. He earned his Bachelor of Science in Electronics Engineering from UC Riverside.
Battery is bad? Change the battery!
Confirm the diagnosis
First, go to your trusted mechanic or auto parts retailer to confirm this. They have the equipment to test the charging system (starter, alternator & diodes, battery).
Get the failed part replaced.
If the battery is bad, replace it promptly – or at least, when you can afford it. But, as said above, you need to make sure that this is the right call.
Batteries aren’t cheap. They can cost $100 or more.
But, not changing your battery can also become more costly. These down-the-road headaches can be very costly.
After getting the proper diagnostics, you'll find out whether or not the battery was the culprit. Sometimes, you'll end up finding out that the true culprit was actually the alternator!
If it ends up the alternator is bad, get a mechanic, or yourself if you’re handy, to replace the alternator.
If the diodes are bad, either get an alternator rebuild or get a new alternator (comes with it). Of course, it's also increasingly important to understand that if the diodes are bad, there must have been some sort of damage that caused them to fail. Mostly, this could be attributed to heat issues. Namely, either a really hot environment or overly hot working conditions under the hood. Check the cooling system and make the engine bay isn't getting ridiculously hot.
Or, it could have just failed on its own!
Be honest about the results
Remember: don’t fight the results here. If their equipment says your battery is bad even though it’s technically working, it’s going to cause failures later on. A failing battery may lead to other components failing.
But, also remember. Looking for a failed battery may also lead you to finding out something else may have also failed.
Always be ready to cough some money up -- no matter what happens. Good luck!