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I want to install these new powerful headlights but they use around 100 watts. I have a 12v 45Ah battery which gives me around 540wh. Now I know that's not even half but when you factor in all the other electrical components I feel it could really dip into my battery and go over the half mark of power consumption.

The battery is a Amstron 12V / 45Ah Sealed Lead Acid Battery w/ R Terminal for a Dodge Challenger 2013

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    If those 100W headlights take more current than your OEM lights, you should upgrade the headlight wiring as part of the install. If the OEM lights are (say) 85W then you should be OK, but if they're more like 40W then you will be asking for trouble.
    – TMN
    Commented Jul 22, 2016 at 15:49
  • Not asked but worth checking: Are the new light legal to use on the street? There are all kinds of laws on how much output you may produce and how high the beams are allowed to be.
    – Hennes
    Commented Jul 24, 2016 at 12:33
  • Hahah, you know forgot all about that.. Need to do some research.
    – LostPecti
    Commented Jul 24, 2016 at 15:47

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So, the real question here isn't "can my battery do it," but "can my alternator do it?" All of the normal running load of your car should be supplied by the alternator.

The battery is there to start the engine and to provide for high short term loads (e.g., the horn or maybe lights at idle).

You can think of the battery as storage for electrical power, it handles loads when the alternator is off-line (when the engine isn't running) and it also provides reserve capacity when short term electrical requirements of the car can't be met by the alternator (for example when the engine is idling).

The alternator provides power to recharge the battery after starting (or any other time when the battery has been drawn down), but it must also provide enough power to handle the normal loads of the car – otherwise just driving the car will drain the battery and eventually the battery will be drawn down to the point where it can't provide the power to start the car.

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  • Sorry man. I am just getting into cars and learning all the technical terms. I thought the alternator job was to simply charge the battery, not run electrical components?
    – LostPecti
    Commented Jul 22, 2016 at 13:28
  • As I reread I am kind of understand what you mean but can you elaborate s bit?
    – LostPecti
    Commented Jul 22, 2016 at 13:30
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    Basically, when the car is running, the alternator should put out enough power to power all of your accessories. Otherwise, your accessories would drain the battery. When you are idle, the alternator may not be putting out enough power as it is not spinning fast enough, so you rely more on your battery. This is why you will sometimes see lights dim at idle.
    – rpmerf
    Commented Jul 22, 2016 at 14:00

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