# battery or not



## nismoracr (Sep 26, 2002)

when im in my car with the headlights on and the radio and i put up my windows all my lights in the car dim. i just replaced my alternator like two months ago, anybody got any ideas on why this would happen


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## Token Moron (Mar 28, 2003)

possibly......check the voltage in your battery, also do u have a sound system? because if so, that would more than likely be it


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## UNISH25 (Aug 12, 2002)

Hmmmm..your lights go dim because something is chewing up your voltage. 
Solutions
1.) Battery voltage is low and you need to replace the battery.
2.) If you have a sound sytem running (a high wattage one 400 or more) then you should get another battery or get a capactior.
3.) Your alternator could possibly(but most unlikely) be damaged.


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## ccroaddog (Jun 20, 2002)

schucks does free battery testing to see if its low... or just go out and buy a red top


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## UNISH25 (Aug 12, 2002)

Huh??? Free battery testing??? Just attach a voltmeter across the top of the battery and see if its reading 12Volts...If its less than 12 then the battery needs replacing...If its higher than 12 then its not the battery!!


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## holy200sx (Jan 8, 2003)

lol. i have a hella bad system, im killing my alternator slowly but surely..


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## azkicker0027 (May 31, 2002)

hook up the voltmeter, make sure you have at least 12 volts, crank the car and see if the voltage drops below 9.6volts, if it does, battery is getting weak, then when running see how much the battery has, because that is how much the alternator is charging, or trying to meet, this is just basically monitoring the battery voltage at different conditions, even check out how much it drops when things get dim....when you play with the accessories....


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## ccroaddog (Jun 20, 2002)

UNISH25 said:


> *Huh??? Free battery testing??? Just attach a voltmeter across the top of the battery and see if its reading 12Volts...If its less than 12 then the battery needs replacing...If its higher than 12 then its not the battery!! *


no your wrong...

just because a battery test 12 volts doesnt mean that the battery pushing out enough amps to crank over properly... now yes if the battery test like 10.5 volts there is something wrong with the battery

just because a 9 volt battery tests 9 volts doesnt mean its going to work


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## Ninety-Nine SE-L (May 5, 2002)

I have a red top, same thing for me, same in my mom's maxima. Headlights on, and when I roll up my windows, the headlights dim a bit. There's nothing wrong. Window motors eat up some power.


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## ccroaddog (Jun 20, 2002)

the windows do suck a lot of power


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## UNISH25 (Aug 12, 2002)

ccroaddog said:


> *no your wrong...
> 
> just because a battery test 12 volts doesnt mean that the battery pushing out enough amps to crank over properly... now yes if the battery test like 10.5 volts there is something wrong with the battery
> 
> just because a 9 volt battery tests 9 volts doesnt mean its going to work *



Hey man, thats it!!! Ima have to get more technical on all you peeps that keep hatin on my shiz. 

I guess 4 years of engineering school wasn't worth it! LOL!!
Iiight...Listen up....NO I'm not wrong(sorry for the rudeness, but its true)!!!

If a battery is testing 12 volts....
Lets see...according to ohms law...V=IR. V=voltage, I=current, R=resistance.
Lets assume Resistance is the same all the time, therefore its constant in your car... The equation reduces down to 12=I*R. So I is dependant on V. If the battery tests 12 volts, then yes! It can pump out the required current! Assuming R does not change! It has to be able too! Ohms law prooves that!

Now when we start the car, we use 12 volts, the 12 volts go through inductor coils...when it goes through the coils, the voltage shoots straight up!!! Giving us the spark within the plugs.

Now...suppose you use a 9v cheap radioshack battery(those little square ones...) with a two 1.5volts batteries in series. Thats 12 volts! In theory, this is just as good as the 12volt car battery. 
Thus, in theory this will absolutely work!!! IN THEORY!!!**IN THEORY!!!!!!!! 12=I*R. The 12volts in the battery would be converted through the coils, and give the high voltage needed to start the car.

In reality...You'll most likely blow the shiz up outta those little batteries. That batteries would only be able to withstand a certain amount of current before it heats up and literally blows up!!(SO DO NOT EVEN THINK OF TRYING IT, UNLESS YOU WANT CORROSIVE ACID ALL OVER YOUR FACE!!)

Your car battery is big because it can pump out more current. About 300-600 cold cranking amps depending on the battery! If your battery is reading 12 volts, then it will give you the power required to start your car!!! It has to!!!!!!!! This is proven by Ohms law!!! The electrons will be come outta that battery easily!

If the battery is 11/12 volts or less...then it might not! The voltage will be converted but not enough to spark the plugs.
Less electrons will come out! If it is more than 12 or 15 volts it will work, but it might blow up something in your car. Like alarm systems and radio! Because of the high voltage

Now suppose your voltage is 12 volts and your cars not starting. This means only a couple of things!
The only case I can think of is if the resistance in your battery is increased...
V=I*R.
V/R=I
As you can see from Ohms law if you increase the resistance the current gets lowered. If the resistance of your battery gets increased, then the amount of current your battery can supply will get lowered.

How can this happen you ask?
If your battery is hot, then its resistance is probably higher. Therefore the current you are getting is lowered. And your battery might not supply the required current needed to start the car.

Also if you apply multiple loads, while starting the car then it will fairl. IE Speaker systems, power windows, headlights, these all apply a load across the battery! Thus making the required voltage to start the car lower than needed!!!!

So if your battery is 12volts, I can assure you 100% that your battery will be able to supply the current needed to start your car! Ohms law states it!

PHEW! SORRY FOR THE INDEPTH STUFF, BUT PEOPLE BE HATIN!


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## UNISH25 (Aug 12, 2002)

1997 GA16DE said:


> *I have a red top, same thing for me, same in my mom's maxima. Headlights on, and when I roll up my windows, the headlights dim a bit. There's nothing wrong. Window motors eat up some power. *


The headlights dim when you roll up your window, because you apply a "load" across the battery.

If you apply multiple loads across a single battery then the voltage across the battery will decrease!


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## UNISH25 (Aug 12, 2002)

nismoracr said:


> *when im in my car with the headlights on and the radio and i put up my windows all my lights in the car dim. i just replaced my alternator like two months ago, anybody got any ideas on why this would happen  *


By the way, the alternator does not supply current unless the engine is running. The only function of the alternator is to supply current to the car when the engine is running and to recharge the battery!


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## Ninety-Nine SE-L (May 5, 2002)

UNISH25 said:


> *The headlights dim when you roll up your window, because you apply a "load" across the battery.
> 
> If you apply multiple loads across a single battery then the voltage across the battery will decrease! *


 Well, that's pretty much what I'm saying, it's completely normal. It's just like trying to accelerate with the AC on. Just like the battery, the AC puts extra work on the engine and the engine can't propel the car as easily.

Just to make that technical part clearer, each electronic accessory takes a certain ammount of current (Amps). Window motors take a good amount of current (especially when you roll 4 up at once like me). I could be wrong on a few of these upcoming numbers, but a typical car battery can support a temporary amount of 600-800 cold cranking amps. But normally, you will not ever need anymore than 100Amps (unless you have an electrical problem). The starter pulls about 75A and the headlights pull about 4.5A per bulb). A typical AA battery can only support maybe 2 amps max. I have a digital camera, I'm not sure what it draws from the batteries, but when I take out the batteries, they are litterally too hot for me to hold on to. If you overload the battery, it cannot move the electrons fast enough and the cells (usually a paste) will heat up and eventually explode.


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## ccroaddog (Jun 20, 2002)

UNISH25 said:


> *Hey man, thats it!!! Ima have to get more technical on all you peeps that keep hatin on my shiz.
> 
> I guess 4 years of engineering school wasn't worth it! LOL!!
> Iiight...Listen up....NO I'm not wrong(sorry for the rudeness, but its true)!!!
> ...



i would reply to that but i didnt want to read the whole thing


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## IXLR8se-r (Apr 14, 2003)

UNISH25 said:


> *Hey man, thats it!!! Ima have to get more technical on all you peeps that keep hatin on my shiz.
> 
> I guess 4 years of engineering school wasn't worth it! LOL!!
> Iiight...Listen up....NO I'm not wrong(sorry for the rudeness, but its true)!!!
> ...



i will have to agree with this, in the process of obtaining my BSME degree, which an electical class was a demanded course, owned


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## UNISH25 (Aug 12, 2002)

ccroaddog said:


> *i would reply to that but i didnt want to read the whole thing *


LOL...sorry for the WHOLE electrical theory, just wanted you guys to know I wasn't an electrical idiot. AHHH...4 years of engineering school was probably worth it then..??? NAHHH!!! BSEE


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## sethwas (Apr 30, 2002)

Check your grounds.
The windows use tiny 22-24 guage wires. Make sure all the grounds are correct. If they aren't the batterys 'load' is constipated. If all grounds (inside the engine) are corrosion free they will work better. THe only problem is finding which ground is the one thats bogging down the car. Best to replace all of them.
If your car is over 3 years old there is an almost guarantee that some of your wires are bad.

Seth


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## ccroaddog (Jun 20, 2002)

UNISH25 said:


> *LOL...sorry for the WHOLE electrical theory, just wanted you guys to know I wasn't an electrical idiot. AHHH...4 years of engineering school was probably worth it then..??? NAHHH!!! BSEE *


isnt true though if a battery reads 12 volts doesnt mean its in full working order. And i will never question your knowledge again... if you would have answered first like you did the second time i would have just agreed. Anywho no hurt feeling :cheers:


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## UNISH25 (Aug 12, 2002)

ccroaddog said:


> *isnt true though if a battery reads 12 volts doesnt mean its in full working order. And i will never question your knowledge again... if you would have answered first like you did the second time i would have just agreed. Anywho no hurt feeling :cheers: *


LOL...no offense taken man! We in good terms now. If a battery reads 12 volts...then you know everything is aok in it! 
Here...do a test. If you have a walkman with batteries in it..the next time the walkman runs out of power read the voltage on the batteries. They should read something less than 1.5 volts. The batteries have to be fully discharged by the way...
Lol...I answer like that, because people just want the facts. They don't want the whole technical theory..thas why.


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## ccroaddog (Jun 20, 2002)

i should test my batt in my car that doesnt work now......hmmm since your a expert i would like you to answer this question.


Are caps worth it in car audio or is it better getting something different??

i think i might know your answer but humor me and the thread


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## landlord (Jun 11, 2002)

my electronics teacher always said as long as a 12v batt never reads below 7v than the batt should recharge fine any lower than that, the batts ruined and will never come back. my 2cents. my lights dim every time i roll up the windows, even with a new battery and altenator. its very slight but they do.


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## landlord (Jun 11, 2002)

also its been awile sence i used the old electronics training, but i thought resistance went down when heat went up, or does that only apply to resistors?


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## Ninety-Nine SE-L (May 5, 2002)

I've taken my battery all the way down to nothing before when I left my headlights on. Wouldn't that be 0 volts (well, maybe a small fraction)? My battery charged back up just fine.


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## landlord (Jun 11, 2002)

1997 GA16DE said:


> *I've taken my battery all the way down to nothing before when I left my headlights on. Wouldn't that be 0 volts (well, maybe a small fraction)? My battery charged back up just fine. *


maybe it was .7v shit like i said its been awile, lol or was that the voltage npn transistors turns on, hell its late and im getting tired lol. im a little rusty i was hoping unish25 could refresh my memory anyway.


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## UNISH25 (Aug 12, 2002)

ccroaddog said:


> *i should test my batt in my car that doesnt work now......hmmm since your a expert i would like you to answer this question.
> 
> Are caps worth it in car audio or is it better getting something different??
> 
> i think i might know your answer but humor me and the thread *


It depends on the situation. You say you have a sound system. 
So guess what happens when you attach that sound system to your car battery...
You apply a really really gigantic load on the battery. So...If you place multiple loads across one battery, the voltage on the battery starts to drop!
What the capacitor does, is prevent the voltage from dropping rapidly! The capacitor stores charge, and when the voltage starts dropping, the capacitor releases that charge to hold the voltage up!

Think of it as a big water tower...When the water supply starts to run dry...the water tanks release the water to keep the pressure up and the water flowing.

So if your lights are dimming here and there, then it probably is worth it to get a cheap capacitor. If its not then you really don't need one.

How you like the explanation??? Humorous enough?


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## UNISH25 (Aug 12, 2002)

landlord said:


> *also its been awile sence i used the old electronics training, but i thought resistance went down when heat went up, or does that only apply to resistors? *


LOl...its actually quite the opposite way. Resistance increases in heat, and decreases in cold. Thats why peoples cars in Russia die faster...they in the cold
V/R=I, thus less resistance = more current the batteries juicing out!


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## UNISH25 (Aug 12, 2002)

landlord said:


> *my electronics teacher always said as long as a 12v batt never reads below 7v than the batt should recharge fine any lower than that, the batts ruined and will never come back. my 2cents. my lights dim every time i roll up the windows, even with a new battery and altenator. its very slight but they do. *


Hmm...I'm not experienced on how the battery recharges, but usually the voltage does not matter. A battery can recharge no matter how low the voltage gets. It's just chemicals inside it...

But that .7 is something else...Another boring lesson!!!
Our alternator(after going through a voltage regulator) produces AC current, its like a mini generator. 
the current swings from +12 to -12 in a sine wave. When the voltage swings into the negative range -.7volts to -12volts , what happens is that current would leave the battery instead of going in!!!!! We don't want that to happen, we're trying to recharge the battery, not drain it!! So they put a big diode to prevent the voltage from draining in the battery. The diode gets rid of that negative region on the sinewave...And thus recharges the battery only. If that diode ever fails(then good luck recharging your battery!!!). 

If you want your lights and windows to stop dimming, then get a optima battery. I think they produce something around 15volts or so...not to sure about this. They made up of better stuff and longer lasting

 
I hope that refreshed your memory...hey why is everyone sleeping?????


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## ccroaddog (Jun 20, 2002)

UNISH25 said:


> *What the capacitor does, is prevent the voltage from dropping rapidly! The capacitor stores charge, and when the voltage starts dropping, the capacitor releases that charge to hold the voltage up!
> *


I know what caps do (i have two) But thanks for the water comparison. . I was hopping you would answer by using old tube tv capacitors or mini 100 farad caps(say it in a car audio magizine) that hold more power than a 1 farad cap does and you could run 4 guage wire for a 3000 watt rms system.

Anywho i would say for any car audio system would benefit from a red or yellow top batt and one cap.


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## UNISH25 (Aug 12, 2002)

No problemo man! If you guys ever have any electrical problems in your car, or need some electrical advice just im me...or message me or something. I'll always hook you up.

I guess that 4 years of engineering school was worth it


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## ieathondas (Mar 12, 2009)

*How batteries work*

I suppose I'll clear up these battery theories for anyone who searches this topic in the future.

First of all, a bad battery will give you a false alternator test. The only way of being able to test an alternator (ie diodes, regulator, output volts, etc) is to first test the battery using a load tester, if the battery tests good you can then test the alternator.

Second of all, factors contributing to why a battery might be bad:
1. The cold cranking amps are low. This would prevent a car from starting regardless of voltage or charge.
2. The voltage is low/ won't hold a charge. This is an obvious bad battery.
3.the battery has a dead cell. The Volts can be 13.5 and the charge can be 100% but the battery is bad.
4. The battery has leaked acid and will be obviously bad.


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## ieathondas (Mar 12, 2009)

The voltage of a battery is irrelevant it only needs to be 12-13.5 volts. This is simply because a car does not rely on the voltage of a battery past the point of ignition because it is then being ran by the alternator. An alternator already puts out roughly 14.5 volts giving the car the constant 12 volts it needs to operate as well as extra voltage to run accessories and overcome internal resistance from the battery. As was stated if the diodes go bad the battery in fact will not be getting charged/ fully recharged. Additionally if the voltage stabilizer was to go bad you would no longer be getting the amount of volts you need to run the car and accessories, hence dim headlights/ flickering lights.


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