An interesting twist to the circuit board saga. The left side battery port on my Twin Force has died and I can only run the mower with a battery inserted into the right side port. I first noticed this several weeks ago when the mower suddenly shut down while I was mowing with just one battery inserted in the left port. At first I thought the battery had discharged, but it still had two charge lights lit, so I switched to the right side port and completed my mowing without further incident. Today I inserted a charged battery in the left side port, and the mower ran for just a second before shutting down and refusing to restart. Again, I switched the battery to the right side port and mowed my lawn without any problems. When I was done, I inserted a second charged battery in the left side port, and when I started the mower it immediately selected the right side port. Normally with two batteries installed, it would first select the left side port and then switch to the right port when the left port battery became discharged. So, basically, I now have a mower with one live port and a second spare battery storage compartment. I have to swap the batteries when the first one becomes discharged, but at least I don't have to walk back to the house to fetch another battery. This mower is over four years old, so it is out of warranty to get a circuit board replacement, and I'm not going to bother purchasing a replacement as long as at least one battery port is still functional.