My 2008 Mustang GT’s battery has given up the ghost. I plan on replacing it tomorrow as soon as I can. I have a couple errands to run before I can do so.
The battery died while on a car wash conveyor with the headlights on earlier today…they shut off the engine with the lights on for over five minutes, so I am sure that didn’t help.
Guy at the wash had a full-sized charger and we got the car started within five minutes. Good.
I left it running when I went to pick up my kids shortly after at school, so it was fine.
My girlfriend and I hung out later and every time she went out to smoke, I started the car up and while the battery chugs and clearly needs replacing, it started.
Right after she left I tried to start the car again and the battery was dead.
I have a small Black and Decker charger that I bought for my lawn tractor a couple years ago. Ten minutes after I hooked it up on the 12 amp setting, my car will now start.
I need to use this car tomorrow morning. The question is, is it okay to just leave the charger plugged in and charging the car overnight? I don’t want to blow anything up. I can disconnect it and hopefully charge the battery to get it started tomorrow morning if I have to.
I am wondering if I am risking anything leaving it charging overnight with the hood up.
Definitely not on a 12 amp setting. It could boil the battery dry, possibly making it totally useless. It would probably be okay on a setting of two amps or less, but the safest bet might be to wait until morning to hook up the charger.
I’m assuming that meant 12 volts and not 12 amps. Your typical little black and decker type charger can’t put out anything close to 12 amps of charging current.
It should be fine.
If it does actually have a high current setting like that, put it on a low current setting and let it charge overnight. That will give you a much better charge than a quicker, high amperage charge.
Starting the car puts the most strain on the battery. After the engine is running the alternator takes over the system’s electrical needs. It also charges the battery. Chargers typically “trickle” charge the battery. That is, a small current over a longer period of time. Overnight is sufficient to charge it up enough to get you started in the morning. If you can open the caps, check the water level. It should be above the plates. If not just add tap water.
Some advice: When you buy a new one go for the one with the most “cold cranking amps” that you can afford. Winter is coming and that is murder on a battery.
I would add that if you do a lot of short trips, especially in the winter with heater blower, demister, de-icer, and lights on, it is a good plan to give it a once-a-week overnight charge just to keep it topped up.
Update: the battery was definitely cheesed. And yes, my little Black and Decker charger does in fact say 2/6/12 amps on it.
An add on question: can a dead or almost dead battery cause the wrench light on a car to come on and for the car to run shitty? This happened on the way from my son’s football game over to AutoZone to replace the battery.
I had to jump the car to get going, but it started fine. But while driving the wrench light suddenly came on and it was shifting really rough, even with it being a manual tranny. I am assuming possibly some kind of extra stress on the alternator from the battery failing to charge or something similar?
Anyway, once the new battery was in, the car ran fine and the wrench light did not reappear.
If the battery goes totally dead (or is taken out) the computer will reset and the car will drive like shit for few miles until some of the parameters get back in check. You’ll find that when places like Batteries+ change your battery they’ll plug a small battery into your lighter just to maintain some kind of charge on the system.
Just a word of very experienced advice: if your battery is more than two years old and lets you down, even once, in any way, replace it as soon as you can. Don’t think it was a one-time occurrence. Don’t think you’ve still got four years left on the warranty. Once a battery fails, it’s just waiting to strand you in the most inconvenient possible way.
That includes failure from known causes like leaving lights on until the starter won’t even click. Once a battery is run down that far, it’s permanently damaged and will never be truly trustworthy again. One time, in cold weather and a little extra drain from leaving a radio or lights on… and blammo. I mean, no blammo.
I’ve used those small B&D chargers.
Those small chargers are either full automatic or a taper charger. In any event it would not charge at 12A all night. Charge would go to near zero and stay there.
Charging the battery more slowly (lower amperage) allows the charge to migrate into the interior of the plates. A faster charge ends up mostly charging the surface of the plates. So basically you end up with a better charge if you do it slowly overnight than if you charge it quickly on a higher current.
Most cars use the battery for the bulk of the voltage regulation and filtering. If the battery is pretty well futzed you can end up with a low voltage on the entire electrical system and erratic voltage swings caused by the alternator that aren’t filtered out since the battery is so dead. That can not only cause the computer to malfunction (causing the check engine light, wrench, or whatever indicator your car has, in addition to the engine running poorly) it can in extreme cases actually cause damage to some of your car’s electrical components.
What was really strange, at least to me, was that the battery gauge was showing a normal reading during the entire 30 minute drive to Autozone while the wrench light was on and the car was running all rough. I would have assumed that either the gauge or the battery light would have indicated a problem. Perhaps the alternator was working overtime to keep things going?
I honestly have no idea. Car runs like a champ now with the new battery. The old battery was five years old, so it was time anyway. Damn a new battery for my Mustang is NOT cheap either. $130 for a decent one.
First of all, what “battery gauge”? Was it a voltmeter, an ammeter or an idiot light? Keep in mind that many “gauges” in modern cars are essentially idiot lights with two or three fixed positions of the needle. (Particularly temp gauges; they have a “cold” position, a very wide “normal temp” position and an “overheating” position, and nothing else.)
If the gauge is a voltmeter and the charging system is working, it will show normal operation pretty much regardless of battery condition.
What is it telling me when the reading is in the normal range while I have a dead battery, the car is running and the wrench light is on on my drive to Autozone? The car literally ran like shit. I can’t help but wonder if it went into limp mode.
I have always wondered why car manufacturers switched from ammeters to voltmeters for the charging gauge many years ago. My 1939 Plymouth has an ammeter. I don’t think ammeters have been used for maybe 30 plus years.
Was it cheaper to manufacture a voltmeter? Or is there some other good reason?
