Is it my battery or my alternator thats going....

[The Stigenator]

I'll be taking it to the dealer to check the charging circuit.. but i thought i'd poke ATTG's brain.

My 2009 Acura TSX was sitting idle for 3 weeks while I was on vacation. I came back on Friday night. Saturday morning, tried starting it, would not start. ABS malfunction came on, all sorts of warning lights.

I put it on my bench charger at 10 amp auto mode and let it sit an hour. It showed it holding steady at 2 amp charge rate after an hour. The 2amp charge rate is trickle mode and tells you that the car is 75% charged.

Anyway car starts no problems. I go out, leave a friends house, car has trouble starting. I get it started somehow, run to fry's electronics, pick up what i wanted. This time I ran the car a minute with headlight and everything off. Car started once I got back, but had difficulty.

I put the car on the charger again for 9 hours, it reached 0 amps, so I assumed it was charged fully.

Problem> Car still has trouble starting. Its not the starting motor, its having trouble turning over, its so bad that the navi unit has gone into lock down mode because it did not get power.

The car runs fine when it starts, the alternator obviously is kicking in fine, but I think the battery is on its last legs.

Its an Acura battery, installed 07/09, its got a 100 month warranty. The OEM battery failed after almost a year and the dealer replaced it with that new battery which is now failing..

 

[JCH13]

The battery may very well be damaged now, but it sounds as if you also have another issue. Possibly the alternator or charging circuit that is causing you to chew through batteries at an alarming rate.

 

[LTC8K6]

Dead cell in the battery?

 

[The Stigenator]

okay load tested it at home, its the battery.

Apparently Acura batteries are known to fail around 36 month time frame, most people are lucky to get more than that.

With that said I am off to Costco to get a kirkland battery. Thank god the Miata still powers up no problems.

 

[phucheneh]

There's really no way anybody could know whether it's your battery or alternator. Just gotta test them.

How did you load test? You check charging voltage, too?

Your car running is not proof of proper alternator function. It's easy for the alt to produce enough power to run, but have insufficient voltage and/or charging capacity to keep the battery from going dead.

 

[The Stigenator]

I had forgotten I had one of these : Pulled it out of the plastic totes and used it. I bought it for my motorcycle battery.

http://www.harborfreight.com/100-amp-6-volt-12-volt-battery-load-tester-90636.html

 

[phucheneh]

There's simply no way that can dissipate anywhere near 100a. You're better off reading battery voltage while cranking the starter (after charging batt).

I would probably recommend taking the batt to the parts store for a charge and test before you spend any money. Just IMO. It probably is the batt, but you shouldn't diagnose with any inclination towards assumption.

That's the biggest problem I see on the internet...90% chance 'x' problem needs 'y' solution...but I'd rather be needlessly thorough and end up in that 90% than misdiagnose and be in the other 10.

 

[LTC8K6]

If the battery was ok, it would have lasted him a while when he charged it up full with the charger. It failed quickly after being on the charger for 9 hours.

I think that, combined with his load test is enough to replace the battery.

 

[Eureka]

I've had an alternator fail before... generally the car will run like fine if the battery works. You'll have a battery light come up, and after a while the car will just die. If you recharge the battery, the car will run like normal.

You can diagnose this if the battery is holding normal voltage (12-14V), but it quickly dips when the car is on. If the alternator is working, you should see the voltage spike to 14V.

A multimeter is your friend here.

 

[The Stigenator]

Changed the battery to the Krikland special battery, $85 and 20 minutes and a beer later, the car is up and running. Though right after changing the battery, it gave me a little fright as it kept cranking but wouldnt start.. guess the ECU needed time to re-calib or something, but its running fine now.

It starts up right away on the first start, no cranking and cranking to start. It fires away quick!

 

[phucheneh]

If the battery was ok, it would have lasted him a while when he charged it up full with the charger. It failed quickly after being on the charger for 9 hours.

I think that, combined with his load test is enough to replace the battery.

Key quote from OP: 'I assumed it was charged fully.'

It's just best to ditch assumptions when you're talking about something that is typically very easy to check, and may have interconnected failures (i.e. poor charging output causing premature failure of battery). Charge batt. Test batt with conductance tester (like parts store will have) or load test with a voltmeter (and the car's starter). Then check charging voltage with said meter. Bing bang boom done.

Unless there's a parasitic draw or cabling issue, but his description doesn't seem to indicate that.

 

[LTC8K6]

Key quote from OP: 'I assumed it was charged fully.'

It's just best to ditch assumptions when you're talking about something that is typically very easy to check, and may have interconnected failures (i.e. poor charging output causing premature failure of battery). Charge batt. Test batt with conductance tester (like parts store will have) or load test with a voltmeter (and the car's starter). Then check charging voltage with said meter. Bing bang boom done.

Unless there's a parasitic draw or cabling issue, but his description doesn't seem to indicate that.

It's not that complicated. Unless his charger was not working, he's done enough to narrow it down to the battery, imo.

I agree that his methods were not the best/easiest way to arrive at that answer.