Join the Car Talk Community!

Discussion Rules

Welcome to the Car Talk Community!

Want to ask a question or join the discussion? Great! Join now.

Sign In Register

How Much Driving Will Recharge Drained Battery?

Doy!!! I left my lights on for 4 days and completely drained my '98 Volvo S70 battery. After a nice church van stopped to give me a jump, I drove about 40 minutes and stopped the car. I needed a jump to get it started! I thought batteries charged quicker?
«1

Comments

  • edited July 2007
    Head lights on for four days

    I suspect that the battery is gone. That would kill most batteries and damage most of the rest.


    Don't try to drive it any more, as you may be damaging your charging system trying to charge the dead battery.

    Time for a new battery, or at least buy a plug in battery charger and follow the instructions on the charger, but I doubt if it will do any good.
  • edited July 2007

    If your battery were still good it would take but a few minutes to charge enough for an immediate restart, and maybe 20 minutes or less for a full recharge. It appears your current battery is now worthless. Replace.
  • edited July 2007
    wow. I didn't know you could kill a battery by draining it. Darn! So, is that something I could do myself on the street if I buy a new battery?
  • edited July 2007
    Yes, just be sure to disconnect the NEGATATIVE terminal of the battery first. If you have the wrench on the positive terminal and touch any metal part of your car, you might weld the wrench to that part. At the least, it could be very exciting!
  • edited July 2007
    Yup, I trashed a fairly new battery a few weeks ago. I was traveling and my alternator failed, by the time I had the alternator replaced I had drained and recharged the battery several times. It seemed OK for a couple of days with the new alternator, then it completely died.
  • edited July 2007

    A battery in good condition will survive a few total discharges. Your battery was likely on its last legs before the incident.

    Yes, replacing a battery is a simple procedure by the owner. Bring the old one with you when you are ready to buy. You typically get some sort of core charge discount and they will also take care of the disposal problem for you.
  • edited July 2007
    Well, it could be a fried battery. or it could be that the nice church van disconnected the jumper cables too soon, so there wasn't enough charge in the battery to supply the field coil of the alternator, so the alternator output was too low to charge the battery and supply the cars requirement too.

    If it is the battery, better get a new one soon. A bad battery draws excess current and that can burn up the alternator.
  • edited July 2007
    Make sure that all your warning bells and things are working. Some people hear them and just walk away without checking.
  • edited July 2007
    That's nowhere near long enough to recharge a stone dead battery. Yes, it is detrimental to completely discharge your battery. In fact, it's not good to go even below 75% of full charge for any length of time. However, unless your battery was on its last legs, it may be recharged and give you many years of good service. You need to trickle charge the battery to replace the energy lost. It will likely charge at 8-10 amps for at least 24 hours.

    40 minutes is 0.66 hours. A typical alternator may put out 100 amps for example. Much of that can be consumed by the vehicle, especially if you run fans as an example while the battery is trying to recharge. So you're not getting the full charge capability of the alternator while driving. Let's say your getting 60 amps to the battery. 60 amps * 0.66 hour is only 40 amps!! Not nearly enough to work the starter motor which can draw hundreds of amps for short periods needed to crank the engine.
  • edited July 2007
    Oops, that should read "only 40 AmpHours"!
This discussion has been closed.