Thanks in advance for reading and any help you can provide.

Have a 2006 MDX Touring model and the other day the battery light came on (only a 4 month old batter). Then about 8 miles down the road the AC shut off, all the digital displays shut off, the RPM Speedometer and Fuel Gauge spiked when I pressed the gas and flat-lined when I hit the brakes. The car did not turn off and was still drive-able (the car would speed up at a normal rate when I hit the gas and I did not lose power steering control). After about 2 miles of that I heard and felt a hard one time knocking sound as if the car shifted VERY hard. About a mile after that the car was puttering and pretty much un-driveable. I jumped the MDX in the driveway and it started right up, everything working. When I took the jumper cables off there was a noticeable difference in the speed the belts were turning, like you could tell the car just lost 50% of its power.

My first thought was the main battery cable is corroded but not sure what is going on.

 

My first guess is that you were experiencing the quirkiness of a low voltage issue. Get a full proper charge in to the battery and see if that resolved the problem. My work van is a Ford and is the battery is discharged enough the it goes through a period of poltergeist activity. All the gauges will drop to zero, the tach, speedometer, fuel gauge, temp gauge, everything. If we take it for a 15 minute drive to let the alternator get a full charge back into the battery all the weird electronic poltergeists go away.

Basically, modern vehicles require a good amount of power to allow the cars computer brain to function properly. When the battery is significantly discharged, the alternator is putting more juice back to the battery and that leaves the computer under powered and it gets confused.

 

My second thought is that you need a new alternator. The battery light usually doesn't mean the battery issues, it means charging system issues. If your alternator is not functioning properly, the car is running off the battery and the battery is slowly discharging with every spark plug spark, brake light lighting and turn signal blink.

The battery is not designed to run the car, it's only to start the car. Once the engine is running all electronics are run off the alternator which also recharges the battery for the next start. If the alternator isn't powering the electronics, the battery will only do it temporarily until it no longer has enough power to do so.