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.

This will likely be way over your head: Car and Deep Cycle Battery Frequently Asked Questions (FAQ) Section 4

What you need to do is to purchase a hydrometer at an auto store and measure the specific gravity of the cells and look at the relative differences.

That test will likely tell you that the battery is bad.

In order to develop high starting current, the plates in the electrolyte have to be close together. Low electrolyte levels or deep discharge will cause whiskers or shorts to develop across the plates. The battery must be kept charged with a trickle charger over the winter if you expect any battery life at all.

Putting the cable on the chassis is the correct way to jump. In fact it should be the last connection made. This lowers the resistance of the circuit containing the starter.

Follow the safety precautions and test the battery. I'll bet the battery has been abused.

Deep cycle batteries are not typically used for this application. They have a wider plate separation and therefore deliver a lower maximum current. Because of the large plate separation, they can be heavily discharged without damage.

Hi,
What you should know is you have what appears to be a bad battery, you have a functional engine, your switch ignition ground works, you have a bad switch in the safety circuit.
What cannot know yet is the health of the charging circuit, the health of the solenoid, ignition switch (other circuits) and safety switches.
Peace,
Clarke