It might harm them a little but not kill them. Charge them back as slowly
as you can, not as quickly. There's a lot to be undone internally and it
takes time.

Jim

On Sat, Aug 13, 2016 at 12:09 PM Don Hanson <dhanson928@gmail.com> wrote:

> Can complete discharge of brand new batteries kill em? Did I just blow $160
> bucks by leaving the key on in my recently revived diesel?  The truck (f250
> powerstroke Ford) got two Interstate batts.  I found it this morning
> without even enough electrons to move anything on the gauges or light the
> warning lights...Deader than a doornail!  I'm now charging them, or
> trying.    Put a digital meter on each, before I hooked it up...read
> 0.02v....with my battery charger on "manual- 10 amp" my meter is reading
> 12.00v... I am an electrical dunce, BTW...
>