Letting it charge for 30 minutes was the right idea but when it died right after that, I would have suggested the battery had a shorted cell. The next thing, when you said it was just replaced, means there was a bad connection on the jumper cable and the battery wasn't really charging for that 30 minutes. That's why it died right away.
Bad cable connections happens to me all the time. The way to tell is to watch the brightness of the under-hood lamp or turn on the headlights and watch them. Wiggle each jumper cable clamp, then leave them alone when the lights get brighter. If you're using a battery charger with a current meter, the meter will stay on "0" when there's a bad connection.
Be aware too that batteries give off explosive hydrogen gas and wiggling the jumper cable clamps can cause sparks that can ignite that gas. At the very least do not hold your face close to the battery.
That mechanic who said "not to worry this car is known for the battery light coming on for no reason." Is absolutely wrong. If that were true we would be telling that to people on this site all day long. The fact is, we're helping people all day long with cars dieing due to dead batteries. The light turns on in response to a problem and some of those problems are not readily apparent. One third of an alternator can fail which leaves you with only ONE third of its rated output as the most you can get and that's not enough to run the car's entire electrical system. The battery has to make up the difference. A simple and quick voltage test at the battery will not show that and it will look like the alternator is working fine. Only a load test will show that. The common 90 amp alternator will only produce around 30 amps. If you can catch it when the battery light is on, you can do somewhat of the same thing by measuring the battery voltage, then turning on as many things as possible. Turn on the bright head lights, the heater fan on high, and especially the rear defogger. A good alternator will be able to keep up to all of that with the engine idling, and the battery voltage will remain between 13.75 and 14.75 volts. When one third of the alternator isn't working you will see the battery voltage drop as you turn on more and more things. Raising engine speed slightly makes a good alternator more efficient and more productive and will bring low battery voltage back up to normal. Raising engine speed won't help an alternator with one third of it failed
Thursday, February 7th, 2013 AT 10:53 PM