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Hey guys,

For the past few months, I've been getting these warning lights that I have attributed to sensors. (red brake, abs, dsc lights simultaneously or also the airbag light). I've always been kind of stumped because it's always intermittent, so that's what lead me to believe its the sensors. For the past 2-3 weeks actually I've never seen either warning light on. Yet at the same, I can't help guess that this is a sign that I may need a new battery.

I also think I need a new battery because I've owned the car for six years and have yet to replace it (and I can't confirm when the previous owner changed it). So I went to autozone today to get it checked, the lady told me I had a 100 percent charged battery but have a bad battery. I was wondering what this exactly means?

Also, since I'll be replacing it, what's the recommended replacement? I know people on the boards say it's not worth it to get the factory one for the price when some aftermarkets are just as good..

thanks in advance!
 

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That's a ripe old age for an OE battery, in my experience. I've got more like 3 years each out of the 2 I've had so far. I've been buying Interstate, and the life is about the same. Where I live, the A/C hits full blast the second you start up, practically year-round, and I always drive with the headlights on, so my batteries have a hard life.
 

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I also think I need a new battery because I've owned the car for six years and have yet to replace it (and I can't confirm when the previous owner changed it). So I went to autozone today to get it checked, the lady told me I had a 100 percent charged battery but have a bad battery. I was wondering what this exactly means?

Also, since I'll be replacing it, what's the recommended replacement? I know people on the boards say it's not worth it to get the factory one for the price when some aftermarkets are just as good.
I believe the autozone lady is mis-using terms. The battery can be at the proper voltage, but, that really has no bearing as to the state of the charge in the battery. It will however tell you if there is a shorted cell in the battery. Each cell gives 2 volts and 6 cells will give about 12 volts total. One shorted cell will give 10 volts, etc. The lady might be reading 12V and saying it's charged. But, that isn't charge state. Charge state is really kind of nebulous. What you need to do is determined the effective output impedance or resistance. You do that by loading the battery with a high current draw and then measuring the output voltage. The impedance (ESR) can be calculated from the Volts-no load, Volts-loaded and load resistance, ESR = Rload * (Vnoload/Vload - 1). In general terms if the voltage doesn't drop much then the output impedance is very low and that's good. If the voltage does drop a lot then the output impedance is high and that's bad. Autozone should have a box with a meter on the front and large load resistors inside to make this general measurement easy. Now one problem is if the battery is perfectly good, but, just isn't charged (maybe the alternator or voltage regulator has failed and you've been running down the battery) it will fail this test and the store will say it's bad. This test should be performed on a battery that is charged as good as it's going to get.


I hear the Duralast DL49 battery is good, but, might need a block of wood on top to get the hold down clamp to work properly. I didn't want to deal with that s**t so I got the BMW battery and it fit perfectly. I got about 6 years on the original BMW battery. The current BMW battery has been going for 7 years and still going with no signs of needing to be replaced. First battery died because I drained it by leaving the lights on and it wouldn't take a charge. The current battery has never been drained to the point of needing a jump. I think I paid $175 7 years ago (effective cost is about $2.10/month) and installed it myself in the BMW dealer's parking lot.
 

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That's a ripe old age for an OE battery, in my experience. I've got more like 3 years each out of the 2 I've had so far. I've been buying Interstate, and the life is about the same. Where I live, the A/C hits full blast the second you start up, practically year-round, and I always drive with the headlights on, so my batteries have a hard life.

Unless your alternator is dying, what you have on when the car is running has zero impact on the battery. I got 11 years out of my first battery, and I live in WI and drive the car year round.

If you are considering a new battery get the Walmart one. It's a perfect fit and made by the same manufacturer as the OEM battery.
 

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its pretty common when batteries die, they will have full voltage but they cant produce any current anymore. a healthy battery needs to hold the voltage and hold it when there is a huge current on it.
its like your chap, length is meaningless when the diameter is like a chopstick.
 
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