I left accessories running overnight with key in ignition & of course battery is dead. Question is after I get it started from triple A do I have to take a ride to recharge it & if so for how long? Also how do I check the life of the battery?
How Many Miles ?
This is not the best situation for the car and the battery. There are better ways to proceed besides jump starting a depleted battery and calling on the car’s charging system to charge it.
How old is the battery in the car ?
I suggest you have it charged with a battery charger. It takes a good bit of driving to recharge a dead battery. Your car’s alerenator is designed to maintain the battery’s charge, not recharge it when it’s dead.
Theoretically, it will take about 3 hours of driving to recharge a completely dead battery…While most alternators have protective circuits so they can’t destroy themselves from overload while doing this, many have learned the hard way that there are alternators that will fail when pushed to the limit…Instead of calling AAA, buy a small battery charger and recharge the battery that way…
Lead-acid batteries, especially starting batteries, do not like being completely discharged. They will usually recover from this a time or two but don’t make a habit of it as it will shorten the life of the battery…
Only about 15 minutes of driving are needed to restart a modern car, which is really all you need.
There is no need to have a completely charged battery at all times, especially in warm weather. Frequent trips of 30 minutes or more eventually will fully bring your battery to a full charge.
15 minutes of driving enough for a stone-dead battery? Doesn’t sound right to me.
We’re not talking about 15 minutes on a 10-amp charger. Most cars have a charging system capable of putting out 100 amps. Once your car has been jumped, even a short drive will give you enough juice for a self restart. That’s all you really need.
15 minutes is plenty of time to put a sufficient charge on the battery, even if you only have a 65 amp alternator.
Sorry, 15 minutes will put a small charge on a fully-depleted battery, but I wouldn’t trust that it’ll start the next day. I would want to charge it, not rely on repeated trips. As Caddyman said, I wouldn’t rely on the alternator, nor want to stress the alternator, in this situation.
We’re not talking about a ‘weak’ battery here.
I’d agree that it’ll take longer than 15 minutes if the battery was totally depleated, however we also have an unknown variable…we don’t know how old the battery is. Or what condition it’s in.
If it were my vehicle I’d drive it straight to a shop and get the battery charged properly and checked out. Even places like Pepboys and AutoZone can do this properly.
You may have a 100A alternator, but you’re using some of that to power the car and accessories while driving. Maybe if you took a 30-minute highway trip while not using the A/C or anything else, you’d get a decent charge, but if you’re doing any idling at stop lights, forget it.
Charging a dead battery this way will also heat up the alternator and battery, and may shorten the life of both. Plus you will only get a partial charge unless you take a long trip, which isn’t good for a battery either.
I have done this before, left the headlights on and came out to a completely dead battery. I jumped it, drove 5 miles to my apartment, took less than 15 min and shut it down. Started next day, no problem, 5 miles to work. Never went dead again.
I’m sure I didn’t get it fully charged, it probably didn’t get a full charge until the weekend when I drove home, but it did put a sufficient charge for the car to function normally for me.
BTW, the battery was about a year old at the time and it lasted about 5 years, but I never ran it down like that again.
I’m sure you did, keith, but if I’m giving advice to a stranger with an unkown battery and charging system, I’ll tell them to have it charged, every time.
I cannot see a car battery taking a 100 amp charge…it will ruin it by warping the plates due to the high current. here is an example.
On my 89 Mustang GT has an 80 amp alternator…left lights on and jumped it. I do have an ammeter gauge installed…After starting the car without anything else on, the most it would charge was 35-40 amps. It took about 2 hours to zero out the charge as it would drop gradually as the battery came up. Maybe after an hour down to 8 amps or so.
I have had cars with a dead battery due to driver error and after a 10 or 15 minute charge from the alternator it would restart. It puts a surface charge on the battery.
Look at it this way, what comes out in current must go back in as far as amp hours are concerned.
This is just a simple example…
Lets say your starter draws 300 amps and takes you 10 seconds of cranking to start an engine…Now if your alternator charges at 30 amps it will take 10 times that amount ( in time in seconds ) to replace which would be 100 seconds Do the math.
I get tired of seeing posts on here that say it takes a 30 minute drive to replenish the battery after a simple start.
Battery/alternator folklore… It’s almost as good as Motor Oil…'59Bird was very close…
The only alternators that will be harmed by charging a dead battery are poorly designed or defective ones…
I think 59tbird is making my point. I observed a similar situation on my 55 chevy. It had an ammeter. On a normal start, the ammeter needle would jump to about 30 amps, but would be back down to about 3 amps in a couple of minutes. It never went to zero because the engine always had some draw.
Being a 55, quick starting was not always in the cards. This was my first car and I did a lot of “learning” on it. It wasn’t uncommon for me to run the battery very low from cranking the engine during a “repair”. When it would finally start up, it would take a lot longer for the ammeter needle to get back down to the normal area. Once I got a “surface charge”, I did not worry about whether the battery was fully charged or not. It would eventually get a full charge.
Back in those days, everyone I knew would recommend against putting a battery on a charger except to get the car started unless it was a trickle charger. A trickle charger would charge a battery overnight in most cases. Professional battery chargers would kill a battery if left on too long, but were good for a quick charge.