powering a single fog light via battery pack?

Is the fog light meant to run off of a 6V power supply? If it is meant for a car or motorcycle, it is probably meant for a 12V power source.

Just buy a bicycle light. They are pretty cheap.

A 12v bulb will need a 7.2 1400 mah battery to go for 3 hours, if your trying to jury rig this you should go with a rechargeable Drill battery of at least 16v level that way you have plenty of reserve juice

i think it extremely is an electro-hydraulic capacity steerage pump on that one, so it sounds very similar to the alternator isn't producing right. Assuming the force belt is there and not slipping, i might get your alternator output checked. could be a unfastened cord, could be a failing alternator.