…That he knows about. Left on (accidentally not shut off by the operator) is one thing. Stuck on (through no fault of the operator, and often not detectable by the operator) is quite another. He was sure that nothing was left on, and I’ll grant that. But unless he tested the drain on the battery with an ammeter, he cannot be sure that nothing was stuck on.
There are several possible malfunctions that can cause a significant drain on a battery, to the point of rendering it unable to crank the starter after one or two overnights. And some of those malfunctions are not evident and give no clue that they even exist until the battery is found dead, and it cannot be determined whether or not they exist without measuring battery drain with an ammeter.
One example: a body control module that draws, say, 350 milliamps until it goes into “sleep” mode, which it should do an hour after the ignition is shut off. In sleep mode it might draw 10 mA. Other parasitic drains (computer memories, radio memory, etc.) add up to maybe 25 mA. So normal parasitic drain is 35 mA, but if that module fails to go to sleep then the drain is 375 mA, over ten times normal. I don’t know of any way to tell whether the module has gone to sleep or not, or whether the drain is 35 mA or is 375 mA, other than measuring with an ammeter. The first (and only) clue the driver would get is a dead battery.
I’m not saying this type of problem is likely, just that it is possible, and has indeed been known to occur.
Maybe this is a dumb question, but did you check to make sure the battery’s connections are tight enough? The last time I bought a brand new battery my car wouldn’t start on day 3, and it turned out that a too-loose connection was joustled even looser, so there wasn’t enough contact. I fixed the issue by tightening the bolt on the clamp with a ratchet and had no more problems.
AFAIK, it turned out that the battery was, in fact, bad. It only tested out at 258 cold-cranking amps (CCA) … was supposed to be 650 CCA when new. Alternator was tested and checked out fine.
However … after reading the later replies to this thread, it appears that some kind of “phantom” electrical draw can’t be ruled out. Might take the car back to the shop after work and ask for a quick battery test (the battery I bought Monday night was replaced with another new one, not recharged) to see if the new-new battery’s CCA look unusually low. If the CCAs are low, then I guess it’ll be time to break out the ammeter.
…
Slight digression – I bought the Monday-night battery from a big-box auto supply store. After my shop tested their battery and found it to be nearly dead, I went to Big Box to get a full refund. Big Box tested the battery also, found it nearly dead (I was standing right in front of the tester and saw the REPLACE BATTERY message on the little green screen). Big Box tested the battery twice more, and got the same result twice more.
Since my shop installed another new battery yesterday afternoon, I wanted a refund on the apparently bad battery Big Box sold me on Monday. Big Box refused – instead of a refund, they offered to either recharge the bad battery or replace it with another new one. Does that sound like business as usual? I am taking it to Bix Box corporate above the individual-store level … just didn’t expect to get any resistance at all (yes, I have all receipts).
Thanks for all the advice and knowledge shared in this thread
The testers used now a days give a direct reading of available CCA independent of the state of charge (assuming that the battery is above about 6V)
So if a 650 CCA battery reads 258 it is bad, not discharged.
If it makes you feel any better the last big box auto parts store battery I bought was DOA also. It had been sitting on the shelf too long and was dead.
Recharging a battery that reads replace is an exercise in not knowing what the fuck you are doing. It is the automotive equivalent of taking a cart with a dead horse hitched to it and hitching up another dead horse for greater speed. Needless to say a cart with two dead horses attached is no faster than a cart with one dead horse.
You approach with the big box boys should be something along the lines of
Because you sold me a defective battery I had to take my car to the shop and pay for an electrical system diagnosis. This would not have been necessary if your battery was not defective. The diagnosis turned up no other issues with the electrical system, just your defective battery. Since I needed to get home and since I no longer trusted your merchandise, I purchased a good battery from the shop. This is why I want a refund on your defective battery. I should also ask for the diagnostic fees I paid, but I won’t.
I called Big Box Customer Relations line (which was harder to find online than you’d expect, but find it I did). They took some information from me about the transaction and recommended that I return to the local Big Box to speak with the day manager. The day manager granted my refund nearly summarily, though he did mention something about how the battery manufacturer wouldn’t reimburse the store for faulty merchandise. So in the end of it all, I got satisfaction.
This very thing happened to me. I assume my experience is typical: the godawfully vague “Check Engine Soon” light came on, and a couple of hours later all the lights blinked before the battery dropped dead. Of course, the owners manual says you must hie yourself to the dealer when this happens. Of course they would. I’m honestly not too good with cars, but the tech from the Auto Club confirmed my suspicion that it was just the alternator, which of course it turned out to be and not a bad repair bill at all, compared with what’s possible.
