Bad Alternator or Bad Battery

[tyealia]

Hey Everyone.

I recently got my car back from the mechanic i had left it for 2 weeks and the battery died. He jump started me and i drove home for 20 minutes then i stalled near a hill and tried to turn the car back on and battery was dead.

I went to autozone and they charged me for 40 minutes, guy said i needed 40 more minutes but i had to go. I put the battery back in the car and lights went on but car still wouldent turn over.

I have replaced the battery numerous times with the same symptoms.

1. If i leave the car for more than a week without driving it dies.
2. When I have the a/c on, stereo and headlights, the lights will dim and brighten dim and brighten up and down pulsating like 1,2,1,2,1,2.

I was pretty much down to the alternator until the autozone part, guy had charged my battery for 40 minutes so shouldent it have started the car regardless of any alternator?

any theories appreciated

[Artermis]

Hi Tyealia,

Do you know how old your battery is? They break down over time and are able to produce less current. Some batteries also require maintenance - as in you have to top up the cells with distilled water if the battery acid gets low. Some batteries are sealed so you can't do this too.

Cold weather does tend to expose a failing battery, so we've hit the prime time of year when the first cold snap hits and old/tired batteries tend to give up. There are places that can offer a battery health check - I've seen halfords do this before.

You can check your battery connections to make sure they are clean and you have a good contact - this sometimes helps. You can clean the contacts with some emery cloth, wire wool or at worst a bit of sand paper if you have to. You want to have nice shiny metal on both the battery terminal and the battery clamp inside face which makes contact with the battery.

You can test the battery and alternator yourself if you have a volt meter.

With the engine off your want to test your battery's voltage. It needs to be a good healthy >=12.6v for a good working battery.

Then turn the car on. With the car running and no other accessories on (so lights, radio, fans off) the battery needs to show >=13.8 volts if its properly charging.

If you're not seeing that 13.8v or more then i would suggest consulting with a mechanic regarding your alternator.

Leaving your car sat for any length of time will drain the battery. I'd expect a newer battery to manage to survive the week but older one possibly not. The problem would be made worse if you then only do a short journey and have all the accessories (lights, heaters, radio) running, as you dont give the battery a chance to recover it's charge.

Even sat parked there is still a current drain on the battery, the alarm and various systems such as the body computer which keeps the clock date etc on will draw a small current which will drain the battery over time.

[IanL]

All good advice. Just to add, if you leave the car unused for a week or more, it is a good idea to give it a top-up charge using a good quality charger. Car batteries like to stay topped up - deep discharge greatly shortens their life.

If you have a good quality charger, you can use it without disconnecting the battery - just plug the charger in or clip the connectors on. I use this one.

[Capncol]

Also check the obvious such as boot and glovebox lights going off.

[tyealia]

thanks everyone for the great advice, update i took it to autozone and they ran an alternator test which came back saying my alternator is not charging up to par, it works but its not complete so probably over months the battery starts slightly discharging which explains my lights dimming up and down when i idle with a/c on. I ordered a alternator off a 206 scrap that had no faults, should get in next couple of days.

[Artermis]

Good work Tyealia, i hope that fixes your issue.