lead??

i have about 300 pounds of lead plate and a few of those jump start booster boxes my question is would it worth taking to the yard ?...or selling to someone that different plans for it ....

On the jump boxes, look them up and see if they are the higher end boxes or not. The more expensive boxes, the batteries alone are $140-$170 each. Worse comes to worse take the box apart, strip the cables and remove the batteries. If they still hold somewhat of a charge, try a trickle charger and see if they hold a charge. You may be able to get $30-$50 each unit.