A bad battery or faulty battery connection.
What are the symptoms? Will it turn over? Can you turn the headlights on and are they bright? IS there a clicking sound? Did you clean the battery connections? The side terminals really need to be clean to send the best current to the starter especially in the winter. Try cleanign the battery connections FIRST before you go any further then check back with another posting on what you have checked.
A weak alternator and/or battery.
Problem with the charging system. Altenator, Battery, etc.. (may even be a loose belt causing the alternator not to spin fast enough to charge the battery).
I'm not a mechanic / technician but if your battery is overcharging or the headlights are too bright so people are flashing their headlights at you when you are just using low beams ( it sounds like a voltage regulator problem )
turn the key? no start? check the battery connections. clean them make sure they are tight turn the key no start? turn on the headlights if you have bright headlights, the starter may be the issue. if you have no headlights, look at charging the battery after battery charge turn the key tries to start or clicks probably a dead battery if the car turns over and just won't start do you have gas? If the car turns over and tries to start that means the battery and starter are good now you need to find out why you are not either getting spark of fuel.
It is safe to use your bright headlights if there is a car ahead of you within 300 feet.
Yes, it is safe to use your bright headlights. The problem is the driver still might not appreciate it, so it is better not to do it.
first check battery, then remove cables, polish battery terminals and cable connectors, do same at solenoid and all terminals with fine sand paper, steel wool etc. until bright & shiny.
according to Florida handsbook, you must dim your bright headlights within 300 feet of the vehicle ahead.
Start by checking the battery voltage and cleaning the connections to the battery. You can use a voltmeter to check voltage or just turn on the headlights and see if they are dim or bright (low voltage = dim headlights). Once battery is checked and your sure it's not the problem, remove the starter and take it to an auto part store. Many auto part stores will test the starter for free. The clicking can be a lack of battery power, poor connection or faulty starter.
Have your Alternator tested. Sounds like the entire engine is running off just the battery.
If it does nothing at all when you stick the key in..it could be the battery is totally dead. If there is a "clunk" sound when you turn the key..it has to do with the starter, solenoid, or related to the starting area. It could be the battery still (not charged enough to start the car). Turn on your headlights and see if they are dim, won't light, or are bright. If they are bright, it usually is not the battery. No gas. Dead battery. The possibilities are numerous. Start with the easiest and go from there. Is there fuel? Is there power from the battery to make starter turn and make the spark plugs spark?
It is safe to use the bright [highbeam] headlights when there is no oncoming traffic/drivers who could be blinded by the bright light. Also, it is unsafe to use highbeams when there is fog or smoke which would reflect the light back to you, thus reducing the distance which you can see.
The brightness of an incandescent light bulb depends on the voltage applied across its terminals. Connecting one, two, or five light bulbs of the same rating to a battery in parallel will provide the same brightness from each bulb.
Headlights have two filaments, one for dim, one for bright. From your description it appears that one of the high beam filaments is burned out. Replace the bulb.
Low-beam headlights that are not property adjusted can make them as bright as high-bead headlights. They also can cause you to not see the full road ahead.
Battery cables could be loose, battery could be bad, starter could be bad, starter solenoid could be bad, ignition switch could be bad. Turn on the headlights and try to crank the engine. If the headlights dim or go out look at the cables or battery. If they stay bright look at starter, solenoid or ignition switch. The neutral safety switch or clutch petal switch could do it too.
check that the wire on the sylenoid is hooked up. also, check for clean connection to the battery terminals. I have one that looks clean but if it's not bright and shiny, it causes problems.
Because the lights are so bright
It depends on what type of headlight you have. What auto do you have?
do you have a volt guage? If yes shoulf be 12.5 volts or higher. if you turn on youre headlights are they bright or dim. If the battery is good u should be able to turn on the headlights and they will be bright even if u try to crank. If the battery is good u may have a bad starter solenoid. u can try taping on it with with a screw driver handle and give it a couple good waks. If its the orignal battery u may need a new battery, as well as a alternator. what happens as batteries get old, they don't fulley charge, and the alternator overheats trying to charge it. the alternator then fails, and the car will run until the remaining power in the battery is used up. just cause a battery starts the car doesnt mean the battery is good.
Does the headlight stay bright when running? Or just barely? My easy guess with limited info is battery is junk have it tested at the nearest Battery's plus or ? it's free. Check the discharge volts at battery terminals make sure the sled is doing what it's doing. Should be about 1.5amps or higher.