I installed new batteries (previous batteries 6 years old) in my CMM1200 Type 2 mower and it worked fine for 1 mowing but it did not recharge the batteries fully. When I put the charger on it only has the green light. The red light does not light at all. After a couple days the batteries are back to 12 volts even up from 11.6 volts. Do I have a charge problem? Maybe my old batteries were ok and the charger was bad.