AJT123

I've been having an issue with my battery. I noticed that (prior to XM install) that sometimes when left out in the cold the car would have a sort of weak start. Got my XM installed and you can't leave accessories on for five minutes without killing the battery. My XM tuner is a Vaistech (sp?), specifically made for Lexus cars so I don't see how it's the main culprit. I figure I just need a fresh new, heavy duty battery. This can't be an alternator issue, there are no warning lights, and the car charges up the battery quickly after it starts. It just dies very quickly. So what else could it be?

Now what's confusing is I brought it to the dealer and they tested it twice and said the battery was fine. I usually trust the dealerships but I think they're wrong. The battery is six years old and has 50,000+ miles on it. Any insight would help! My gut is telling me to just go to Autozone and get a new, heavy duty battery.

Lavrishevo

iTrader: (1)

Check out the Optima line. They sell them at the local auto parts store.

Gene01

If you have a reasonably accurate Digital MultiMeter (or can borrow one), you can check this very quickly.
For this purpose, you can get one from Harbor Freight for less than $4, and can use it in the future to check flashlight batteries, etc.
After sitting for about 30 minutes, the battery should still read about 12.6V.If it is lower, either it is not charged, it is bad, or you have a significant drain.
To check the charging voltage, start the car and check the battery voltage at idle, and again about 1500 to 2000 RPM. You should see somewhere around 13.8 V or so. If it is lower, you have an alternator/voltage regulator problem.
From your description, it sounds like some load is draining the battery even when the ignition switch is OFF, but that is only a guess at this point.

fensterlip

I would use a voltmeter as Gene01 suggested. It should read from 12.6v to 12.84 volts when fully charged. If it's below this I would put a modern 3 stage charger on it to top it off, let it set for 20 minutes and check the voltage. Make sure it's in this range. If not, it's time for replacement. 6 years is a lot on a battery. As a follow up you should check it also after sitting for an extended period of non-use and see if the voltage is dropping. You could have a parasitic drain from a mis-installed VaisTech but it could also be the battery self-draining from a cell short. Old batteries have sloughed material built up in the bottom of the cell and when it is sufficiently high it will short across the plates.
An Optima or other AGM (Absorbed Glass Mat) battery isn't a perfect choice for this car. The charging system is designed for a Low Maintenance / No Maintenance Flooded cell and the charging requirements are different. An Optima will work for quite a few years but won't be happy. AGM cells are very picky about how they are recharged and the charging system needs to be mapped for it. A modern portable charger will have a switch or other system to detect an AGM versus a flooded cell. An Optima is quite a bit more money and their number one attribute is vibration resistance. Not much of an issue here. I happen to like the top Interstate batteries but there are several good choices out there.

AJT123

Thanks for the replies, guys. Any troubleshooting helps. Keep in mind, that even a month prior to even having XM installed I would notice, after leaving it in the cold all day while working, it would have a somewhat weak start. And with my new XM it would die after me just listening to it in my garage for 5 mins with the motor off... I'm no mechanic but my gut tells me that this new XM puts more load on the battery and that I simply need a new one. I'll get one that's more heavy duty than what is called for.

I'm gonna run by the radio shop tomorrow and ask him to make sure there's no way the system is running when the car is off... But I don't think it is, honestly.

Gene01

The additional load from the XM should be minimal. I would guess that a good battery would run it for 2 or 3 days before it drained the battery to the point that it would not start the car.

honeygee2

Its time for a new battery.