MECHMAN
10+ year member
Senior VIP Member
In any situation where the vehicle is using more current than can be replaced by the alternator, you will expierience a drop in voltage. The bigger the deficit of current demanded from the alternator, the bigger the drop. When you add more batteries, your are basically just increasing the size of the "reservoir", which means that the voltage doesn't drop as much. The reason why you see SPL vehicles with 80 batteries in them is because there is no possible way to get enough alternators on the vehicle to support the amp draw, so they "band-aid" the problem with batteries, and just charge up the batteries in-between rounds with a battery charger.
In your case, if you were to put an alternator on the vehicle that is capable of producing as much current at the amplifier and vehicle use combined, there would be no need to run additional batteries.
A good quality 250 amp large case alternator will produce aprox. 150 amps at idle, and would solve your dimming headlight problem almost completely. Furthermore, the voltage going to your amp would stay closer to the setpoint of the alternator (14.5V) rather than battery voltage (12.6V) and your amplifier would actually put out more wattage. (subs would hit harder)
If that isn't enough to convince you, a stock 110,000 alternator isn't going to like being overloaded constantly by trying to support double the current demand that it was designed to support. It will be running "wide-open" in an attempt to keep the battery at 14.5v, (which will be impossible because of the amperage deficit) and that generates a lot of heat, which is what causes alternator failure.
I guess what I'm trying to say, is that the correct way to solve your problem is with additional alternator amperage.
In your case, if you were to put an alternator on the vehicle that is capable of producing as much current at the amplifier and vehicle use combined, there would be no need to run additional batteries.
A good quality 250 amp large case alternator will produce aprox. 150 amps at idle, and would solve your dimming headlight problem almost completely. Furthermore, the voltage going to your amp would stay closer to the setpoint of the alternator (14.5V) rather than battery voltage (12.6V) and your amplifier would actually put out more wattage. (subs would hit harder)
If that isn't enough to convince you, a stock 110,000 alternator isn't going to like being overloaded constantly by trying to support double the current demand that it was designed to support. It will be running "wide-open" in an attempt to keep the battery at 14.5v, (which will be impossible because of the amperage deficit) and that generates a lot of heat, which is what causes alternator failure.
I guess what I'm trying to say, is that the correct way to solve your problem is with additional alternator amperage.
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