Can i use a battery as like a big cap? and how can i keep it charged in my car, i get batteries with 800 cca?

Question

for 20 bucks, they are brand new, is there a way i can do this? i woudl like to run all my neons off that battery to:)

Answer 1

Batteries and capacitors are much different devices, and aren't used in the same way.  A typical battery can't be charged higher than 12.8 volts, while a capacitor can be charged to a level very close to the alternator voltage of 14.4 volts.  Batteries also have a much higher internal resistance than capacitors, which means they can't maintain their voltage with very high current demands.

When your engine is running, the alternator is the primary power source.  Current doesn't flow from the battery unless the alternator is so overloaded that the system voltage drops to 12.8 volts.  Adding a second battery doesn't change that; it doesn't provide ANY reserve power until the alternator is already overloaded.  A capacitor can't provide nearly as much reserve power as a battery, but it can start delivering current as soon as the voltage begins to drop.  That's why capacitors can be useful in some systems that are used primarily with the engine running; second batteries are generally only useful if the audio system is playing with the engine off.

If your audio and lighting systems require more current than the alternator can consistently deliver, neither a second battery nor a capacitor will help.