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Old 10-10-2012, 09:45 PM
DSXMachina's Avatar
DSXMachina DSXMachina is offline
Bimmerdex 7.4!
Location: New Hampshire
Join Date: Dec 2007
Posts: 11,157
Mein Auto: 335i E92 TiAg 6MT ED
You've gotten some great advice from F2D and ILMC, and you can count me in as a 'second' on their suggestions, though I guess I'm really a third.

I'll add some info for others who might be in a similar situation. There are really 3 types of chargers. There's the more powerful ones which can charge at 12-100 amp rates, they can start a 'dead' car almost immediately to a few hours. Then there's the 2-10 amp units which take overnight or longer to invest enough current to start an engine. Both the aforementioned types cannot be left on the battery continuously, and both often have the ability to charge at a fast rate at first, and then slide on down to a slow rate as the battery 'fills up'.

Neither type is good for long term maintenance. For that you want the category, including the specific model, mentioned by F2D. They are 'smart' chargers and have the ability to determine optimum rejuvenation techniques and flow rates to bring a dead battery back to life. I am told that a battery that has been run down to the point where your directionals won't work can never be brought back to it's full life span, but it seems to me that things like the CTEK do a darned good job.

Now a word about what the dealership told you. Horsepuckey. That's the word. Your driving habits should not be killing your battery. Who are they trying to kid? Eleven miles a day with two start cycles and longer trips on the weekend? That should not be running down a battery that has more capacity than a Mack truck, fed by an alternator that can power a small town.

I know of the device they used to test your battery (a Midtronics tester). I have one! They are great for safely testing batteries, explode very few and don't burn out alternators. Kid techs love them because they are 'high tech', give you a print out to dazzle the customer, and make it look like you're smart as hell. The problem is they don't stress the battery and can't pick up certain failure modes which can leave you on the side of the road.

Analogy: You often get chest pains and are short of breath. You go to Dr. Wetbehindtheears. He hooks you up to an EKG, an EEG, a CIA and an FBI. He says there's nothing wrong with you and sends you home where the next morning you die of a heart attack. Or...

You go to Dr. Oldschool. He puts you on a treadmill and watches your EKG traces rapidly become irregular. He knows you have a problem and responds appropriately.

You went to Dr. W. He didn't load the battery with a good old fashioned scary carbon pile load tester. Those'll pick up a weak battery like nothing else. They also look very impressive as they glow like Chernobyl and smoke like a cold tractor.

So, to put your mind at ease about whether you really have a bad battery or not, here's what Dr. Oldschool recommends. Next Saturday morning press your 'Start' button without your foot on the brake pedal (the engine won't start). Turn on your headlights, your radio and your blower fan at max. Wait five minutes, actually time it. Then turn everything off, remove the key, reinsert the key and start the engine. If it starts as strong as ever chances are they were right. If it cranks the least bit slowly, or not at all, they were wrong and you need a battery. Go back and tell them what Dr. O. said. Be prepared for more horsepuckey.

Last edited by DSXMachina; 10-10-2012 at 10:07 PM.
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