I have a 600 series yard machine and a couple of weeks back when I turned the key to start it, it acted like the battery was dead. I jumped it off from my car with no problem. I had planned to charge the battery but forgot.

The next week when I went to mow the yard, again it acted like a dead battery but this time when I jumped it from my car,connecting to the battery terminals, it acted like there was a dead short, nothing happened. I found that if I connected the positive cable to the started motor then after turning the key on and touching the negative lead to a grounded part of the chasis, the starter turned over and the motor started and ran perfectly. I disconnected cables from battery & connected jumper cables directly to battery cables. Still dead. No response.

Can someone tell me what is wrong and needs to be changed?
Thanks
Ben P.