Battery Drained Within A Day. Bad Ground? Alternator?

[afakhori]

Hey All,

New to the forums. My wife has an 07 RX350 and two days ago she called me telling me the battery light was on, then 5 min later she said it wouldnt even start. I go pick her up and pull the battery and have it tested. O'reilly's says it wouldnt even hold a charge. Since it was the original battery I assumed it was just time for a new one. So I picked up a battery from costco, dropped it in and it started fine. My wife drove to work the next day (about 15miles) and back home fine. As she was pulling onto our street the radio started cutting in and out, the windows stopped working and it started getting prettty sluggish. Pulled the (new) battery and had it checked, was told it was on its last legs of life.

Something is draining this battery hardcore and fast, and I dont know how to figure it out. Has anybody experienced this before?

Any help would be much appreciated.

[pj8708]

Hi Aarash and welcome to the Club.

I'm not really qualified in this area but I think you probably have answered your own question. Many members will say that your battery cables clamps can never be to clean. They insist that a stiff wire cable cleaning tool be used to get the clamps absolutely shiney.

Have you checked the ground?

If the battery is being drained while driving and the alternater is not putting anything back in you know what to look for.

Somebody else may jump in here with some technical knowledge.

Come back and let us know what you find out.

Paul

[dcfish]

Reads like the alternator is not charging the battery...

[afakhori]

Thanks! Do you guys know of a definitive way to test the alternator?

[maseace]

Check the battery voltage when the car is running, it should be around 14V if it's charging properly.

[RX400h]

I agree with maseace. You will need a multimeter to do this. You can get a decent one at Sears for $50 or less. Set to DC volts and touch the red lead to the positive terminal and black lead to the negative. You should see a minimum of 13.5, but no more than about 14.5V while the engine is running.

By the way, a bad alternator should not cause a new battery to be on its "last legs". If that battery can no longer accept a charge, then it was likely not good from the beginning.

[jetfixer01]

If the battery light came on while driving, then the alternator is not charging the battery. As said above you check it with a voltmeter. A charged battery should read 12.6 volts with no load on it. After starting the engine, it should be about 14 volts. The new battery you bought is not on its last legs, it is simply discharged. Any decent battery charger will recharge it. It will need a good long charge, like overnight, before you can expect it to go back to normal duty in the car. Most auto parts stores will check the alternator output for free if you don't have a voltmeter.