What could be the problem? Battery or something else?

Question

For some weeks I noticed whenever I want to start my car (Nissan Primera 2000) it takes a few seconds more to start than the usual turn-the-key-and-voila-ignition. And sometimes it won't start at first try (no cranking and very dim lights), but after waiting for like a minute, I would start.

Now it's not even starting on its own anymore and but when I connect another battery it starts normally in the turn-the-key-and-voila-ignition way.

I suspect the battery has gone bad but the only question I have is this battery is still showing green in the indicator window (if it has gone bad, I believe it shouldn't be green).

And I know the alternator is working fine because when I used another battery to start the car and put my battery back and drove the car for about 1 hour, it started fine. However, when the car sat for about 4 hours it couldn't start on it own again.

So is the battery bad or something else could be wrong? I don't want to buy another battery only to discover it wasn't a battery problem.

Answer 1

The two most likely causes are:

1. Something is wrong with your battery. Your car is more than old enough to have gone through several batteries, so it may be due for one more. There are many ways that a battery can fail, so the green indication might not be telling you the whole story. If the battery is relatively new, it may still be under warranty.

2. A parasitic draw is pulling the battery down. One possibility is a load in the car, but you have pretty effectively eliminated that when you tested by disconnecting the negative terminal. Another possibility is that there is a conductive pathway across the top of the battery. This can happen when the top of the battery gets dirty – especially if some of the dirt is road salts. Unless the top of the battery is spotless, carefully clean it.

If after cleaning the top of the battery you find that it still does not hold a charge with the negative terminal removed then it is a very safe bet that the battery has failed.

Answer 2

It is difficult to say if it is just the battery what is wrong. It might be the battery, or a derivation (I'm not sure about the correct english term for this, perhaps shunt is the correct one. I mean when some faulty circuitry is slowly draining your battery, but not as big as a short circuit) in your car circuitry.

One thing you can try, is this: drive your car for a while and once you get home, turn your car off and get to the negative battery terminal and unplug it (so your car will be unpowered. Take in account that the radio unit will lose tuned stations, date and time, and all that). Leave it unplugged until the next time you are going to start your car (several days later, hopefully).

You can also measure the volts between the battery terminals with a polimeter, just after getting home, and the next time you are going to start your car.

This will try to verify if the battery itself is faulty, or if the problem is somewhere in the rest of your car.

If after umplugging that battery for a time, the volts have dropped a lot when measuring (less than 11v), then the battery is probably faulty. If the battery remains within de 12.5v range, and the car starts easily, then the problems is likely a derivation in your car.

This will not solve your problem, but will hopefully give you some clue in what to check next.