Bad alternator, bad battery, or bad something else? Slow starting 02

[devil421]

02 MDX Navi Touring, 83k miles. No warning lights or MILs observed. This is all over a period of less than two weeks.

Here's what's going on. Slow starting showed up recently, ended up with dead battery in grocery store parking lot. Battery (~2 years old) appeared to just run down over course of a few days of starting and apparently not recharging. Jumpstarted fine and car starts up fast with charged battery so it's not a starter problem or fuel problem. I cleaned corrosion off cables, reattached securely and charged battery to full (95% according to charger). I did NOT remove battery from the car. Car started immediately like normal. Using battery tester I tested the alternator current with car running and headlights on (aftermarket HID, installed for 6 years no problems), reading around 14.5v. According to charger manual this is correct voltage and should indicate no problem with alternator. Alternator belt is tight and spinning and no noticable electrical problems while car is running like dimming headlights or dash lights. Car went right back to gradually slower starting again and now battery is almost dead again several days later. It's back on the charger right now and Im sure this cycle will keep repeating if I let it.

So does this sound like the battery is just beat and can't hold a solid charge anymore? Or is the alternator not recharging it at all even though the voltage reading while running says alternator is fine? Or is there a battery drain that's suddenly popped up? Nothing has been modified in the car in this time period to bring a drain, plus if it was a drain the alternator should just recharge while driving and Id likely not notice the drain since it doesnt go from full charge to dead overnight. It's a gradual slower and slower starting over a few days. Or does it sound like something else going on? I could just go get a new battery and go from there but I was hoping someone had an idea of what's going on. It doesn't make any sense.

[kokerj]

Sounds like a slow drain to me.

[devil421]

What sorts of things cause sudden battery drain? Like I said, the car hasn't been modified in any way and I know drains usually come from things like alarms or whatever.

I did notice what looks like some electrolyte staining around the battery caps. I never thought to check electrolyte levels. I ended up picking up a sealed AGM battery at autozone tonite to try to eliminate the battery itself as problem area. Ill update.

eta: I found a good tutorial on tracking down possible battery drains and will try it out if the new battery doesn't resolve. Since it just got cold I have been running things like the seat heater more. We'll see.

[redlobster]

I didn't read over your whole post but have you checked your cables? We recently had an issue with the postive cable on my wifes 02 mdx.

[Warzau]

Always start simple. Clean posts. I remember my wife's TL was hard starting and then one day didn't start up. Checked under the hood the post were all full of corrosion. Cleaned them up and haven't had a problem since. While you're cleaning check the cables.

[G. COLTON]

It is always best to read posts fully before commenting. Here is what the poster said.

" I cleaned corrosion off cables, reattached securely and charged battery to full (95% according to charger). I did NOT remove battery from the car"

With the 14.5 volt reading on the alternator I would not think that is the problem. However, I would not completely ignore this possibility. It is possible, though unlikely, that the alternator voltage would be correct but still not putting out sufficient amperage.

I would take the MDX by Auto Zone or similar and have then run a load test on the battery.

As has been stated, a short is probably the most likely cause. If you have or can get to an ammeter hook that in the circuit when the vehicle is off and see what reading you get.

George

George

[1604169]

Originally Posted by G. COLTON

I would take the MDX by Auto Zone or similar and have then run a load test on the battery.

Start with this ^^^. Batteries are always a culprit. After that I would look to your alternator.

[devil421]

Looks like it was the battery. The car has been starting quickly ever since I replaced the battery with no sign of rundown at all.

Im also a motorcycle enthusiast and the reports of failing batteries in the 2-wheel world are at an unprecedented level lately. Seems the "cheapy" batteries for cars and bikes (and probably everything else) have a one to two year life span these days. I went with an expensive AGR type Platinum from Autozone and the car has been perfect since replacement. Thanks to all for taking the time to post.