I just bought a new battery to try and fix my cranking problem. It would spin over very slowly as if the batt. was dead. I jumped it using my lawn tractor and it spun over just fine, nice and fast. The new battery is doing the same thing. But heres the puzzler, the battery charger says its fully charged, and it will spin over fine sometimes, then other times it will barily crank over the first couple revolutions, then speed up. could the new battery i bought be defective? or do i have some other problem.