left lights on, killed batt. Charge or replace?

[dghii]

Originally Posted by Allegro

Lead acid batteries are not meant to go below about a 50% state of discharge. At least not often. And in cars that very seldom happens. But once? Your battery should be fine if you charge it fully, i.e. more than just running it in the car for a bit. Put in on a good charger for 24 hrs or more.

Its not that the batteries are not meant to go below 50%, its just that deep cycling LA batteries reduces lifespan.
IIRC, LA batteries will last for 5-7 thousand charge cycles when batteries are only slightly discharged (~80% charged). Same battery good for 5-7 HUNDRED cycles when discharged over 50%.

[piper6909]

Originally Posted by dghii

Its not that the batteries are not meant to go below 50%, its just that deep cycling LA batteries reduces lifespan.
IIRC, LA batteries will last for 5-7 thousand charge cycles when batteries are only slightly discharged (~80% charged). Same battery good for 5-7 HUNDRED cycles when discharged over 50%.

You and Allegro are essentially saying the same thing.

Regardless it's good to know. I may have known that about LE batteries, it just hasn't occurred to me the way you both described it. Now it's more clear to me.