new battery, new ALT, battery wont stay charged

[Silent_White]

The alternator outputs about 12.5 volts when the car is running. The alternator and battery are new, less than a week old... the old alternator and battery had the EXACT same symptoms.

If the car sits for a while it regains enough juice to start just fine. if i try to start it right after i turn it off, the battery is low enough that it barely turns the starter and often kills the battery. A jump will start the car every time, and the 12.5 volts output from the alternator are enough to keep the car running again until i shut it off.

I replaced the battery first, then the alternator.. what next??

Battery cables are very tight and not corroded at all.

 

[turbo98eclipse]

I ask the same questions on all these type questions

Have you tested the alt at the alt? Meaning test the alt with a multimeter: the pos lead on the alt terminal and the neg lead on a ground? This will tell you if the alt is good. If so, then test it at the battery. If there's a voltage drop then there's a short or high resistance in-between the bat and alt. You've now narrowed down your issues

You're looking for 13.9-14.5 at the alt. Default battery voltage is around 12-12.5

 

[dsmtun3r98gst]

Yeah if your alt. output is 12.5 volts then there is something wrong with it. It should be in the 13.9-14.5 range that turbo98eclipse just mention. does your car seem too idle pretty low??

Another thing you might want to check is the cables going to the alternator. if the cables are frayed/loose that can also cause a bad connection and you won't be getting a good charge.

 

[rlacasse1]

Have you checked your alternator fuse? Cause you should.

Have you tested voltage at the battery with the car both running and not running?

 

[turbo98eclipse]

Check belt tension also...

 

[95burgundyesi]

Make sure you have a few good grounds throughout your engine bay. DSMs are just weird when it comes to this area.

 

[ignited Alchemy]

check terminals, test alt, then test the battery.

 

[Silent_White]

the cables at the alt are good. voltage at the alt is 12.7. the 100A alternator fuse in the fusebox under the hood is good. schucks tested my old alt, tested good. belt tension is not loose at all. anyone have a wiring diagram for the 2G alt?

 

[GST with PSI]

Default battery voltage is around 12-12.5

This is incorrect. 12V is an EXTREMELY dead battery. A full charged battery should be at least 12.6V or greater.

The alternator outputs about 12.5 volts when the car is running. The alternator and battery are new, less than a week old... the old alternator and battery had the EXACT same symptoms.

12.5 volts is a much too low charging voltage. Even the static voltage should be higher than 12.5 while the car is sitting not even running. Measured voltage at the battery around operating temp (140 degrees) should increase from anywhere between 13.4V-14.6V while the car is running at approximately 2500 RPM.

DO THIS: Charge your battery until it is FULLY charged (12.6V or higher). Afterwards look at this thread:

http://www.dsmtuners.com/forums/newbie-forum/398192-car-keeps-dying.html

Perform the test I wrote, post the results and I can help you from there.

 

[GST with PSI]

After you verify the alternator is charging like it should be, perform a voltage drop on the positive side of the charging system. Switch your meter to measure DC votls. With the car RUNNING, connect your meter leads according to the diagram below (Positive lead on B alt post see here http://www.dsmtuners.com/forums/newbie-forum/398192-car-keeps-dying.html) . Make sure you have a good connection between your tester leads and the test points. During the test you should see less than 0.2V DC on your meter screen. If you have any much more than that you have a wiring/grounding problem. Please post your results when finished testing.

 

[turbo98eclipse]

This is incorrect. 12V is an EXTREMELY dead battery. A full charged battery should be at least 12.6V or greater.




12.5 volts is a much too low charging voltage. Even the static voltage should be higher than 12.5 while the car is sitting not even running. Measured voltage at the battery around operating temp (140 degrees) should increase from anywhere between 13.4V-14.6V while the car is running at approximately 2500 RPM.

DO THIS: Charge your battery until it is FULLY charged (12.6V or higher). Afterwards look at this thread:

http://www.dsmtuners.com/forums/newbie-forum/398192-car-keeps-dying.html

Perform the test I wrote, post the results and I can help you from there.

Not necessarily. A DEAD battery is only dead if the amperage rating is low due to something like a dead cell IE: extremely high resistance. A battery can read anywhere under 12.5 and still be good, just needing a recharge. The car can still start with I believe atleast ~10v available.

Regarding your statement, if the alt is reading 13.4 ESPECIALLY at 2500, then that is an EXTREMELY bad alternator. 14.5 is ideal alt output

A battery charged over 12.6 (entering the 13v realm) sitting staticly would be considered overcharged

 

[GST with PSI]

Not necessarily. A DEAD battery is only dead if the amperage rating is low due to something like a dead cell IE: extremely high resistance. A battery can read anywhere under 12.5 and still be good, just needing a recharge. The car can still start with I believe atleast ~10v available.

Regarding your statement, if the alt is reading 13.4 ESPECIALLY at 2500, then that is an EXTREMELY bad alternator. 14.5 is ideal alt output

A battery charged over 12.6 (entering the 13v realm) sitting staticly would be considered overcharged

No offense but you are confused. What you said is incorrect. Let me explain. The amperage RATING of a battery will never change. If you mean the amperage output then you are correct in saying a battery's output would be low due to a dead cell. The amperage output of a car battery (typically lead acid) can be affected by many factors including a discharged battery, temperature, load, electrolyte levels and more. The most simple way to test the battery would be to fully charge it and take it to have it load tested by someone with the proper equipment. I am assuming however that because the battery is brand new, none of these things matter. The reason the static battery voltage (meaning voltage measured as if it was out of the car) is low is not because the battery is bad, but because it has yet to get a chance to fully charge in the vehicle.

A DEAD battery is any battery that is discharged. Meaning if it's not reading 12.6V or higher it is undercharged. An undercharged battery could be caused by numerous things, which he is trying to find. A battery with a bad cell is not a dead battery, it's a BAD battery, and can only be fixed by replacing it.

13.4-14.6 volts @ 2500 RPM is the FACTORY alternator output specification at 140 degrees F according to Mitsubishi, not me. Not sure where you are getting your information but mine is from Mitsubishi.

You are correct by saying 13v would be overcharged. There's a very big difference between 12.6v and 13v. Might not sound like it but there is.

 

[turbo98eclipse]

No offense but you are confused. What you said is incorrect. Let me explain. The amperage RATING of a battery will never change. If you mean the amperage output then you are correct in saying a battery's output would be low due to a dead cell. The amperage output of a car battery (typically lead acid) can be affected by many factors including a discharged battery, temperature, load, electrolyte levels and more. The most simple way to test the battery would be to fully charge it and take it to have it load tested by someone with the proper equipment. I am assuming however that because the battery is brand new, none of these things matter. The reason the static battery voltage (meaning voltage measured as if it was out of the car) is low is not because the battery is bad, but because it has yet to get a chance to fully charge in the vehicle.

A DEAD battery is any battery that is discharged. Meaning if it's not reading 12.6V or higher it is undercharged. An undercharged battery could be caused by numerous things, which he is trying to find. A battery with a bad cell is not a dead battery, it's a BAD battery, and can only be fixed by replacing it.

13.4-14.6 volts @ 2500 RPM is the FACTORY alternator output specification at 140 degrees F according to Mitsubishi, not me. Not sure where you are getting your information but mine is from Mitsubishi.

You are correct by saying 13v would be overcharged. There's a very big difference between 12.6v and 13v. Might not sound like it but there is.

No, I wasnt confused-- I was referring to the output, not the rating

By dead I was referring to useless, un-rechargable. I should have been more specific

My info on the alt voltage came from electrical ASEs and every engineering course Ive ever taken. So I dont know-- not trying to argue or anything, but thats just the info Ive acquired over the years.

The MAIN question we should both be trying to figure out is why the OP hasnt updated us on if weve even helped him solve his issue . Since he said his alt output was 12.7 AT the alt, hopefully hes changed that out by now

 

[GST with PSI]

No, I wasnt confused-- I was referring to the output, not the rating

By dead I was referring to useless, un-rechargable. I should have been more specific

My info on the alt voltage came from electrical ASEs and every engineering course Ive ever taken. So I dont know-- not trying to argue or anything, but thats just the info Ive acquired over the years.

The MAIN question we should both be trying to figure out is why the OP hasnt updated us on if weve even helped him solve his issue . Since he said his alt output was 12.7 AT the alt, hopefully hes changed that out by now

Ahhh yes, ASE's. I have a few of them under my belt also. A1-A8 to be exact. Although we both know ASE's definitely aren't rocket science, they do cover the basics and prove you can read and write. I'm definitely not trying to argue, just misunderstood what you said.

I do hope he gives us and update on where he stands with this problem. I hope we both aren't wasting key strokes....

 

[dsm'r sk1mp]

I have a similar problem, thought i had it fixed but I didnt. The alt has been checked, at cold running, normal temp and at twenty five hundred RPMs. The fuse looks fine nothing bad about it. The car has a brand new battery and alt. I have redone ALL grounds, All positives in the car all the way to the damn stereo. The battery then continues to die.

 

[GST with PSI]

I have a similar problem, thought i had it fixed but I didnt. The alt has been checked, at cold running, normal temp and at twenty five hundred RPMs. The fuse looks fine nothing bad about it. The car has a brand new battery and alt. I have redone ALL grounds, All positives in the car all the way to the damn stereo. The battery then continues to die.

Try the voltage drop test I put up in post #10 and let me know what your results are.

 

[turbo98eclipse]

Try the voltage drop test I put up in post #10 and let me know what your results are.

^^that and you may also want to tell us what voltages youre getting/got when you did the tests

and to GSTwithPSI: no, no arguments or hard feelings-- 2 heads are better than one so its all bueno

 

[rlacasse1]

I have a similar problem, thought i had it fixed but I didnt. The alt has been checked, at cold running, normal temp and at twenty five hundred RPMs. The fuse looks fine nothing bad about it. The car has a brand new battery and alt. I have redone ALL grounds, All positives in the car all the way to the damn stereo. The battery then continues to die.

I would check the fuse out further. Mine looked fine until I tried pulling it out and it disintegrated in my hand

 

[turbo98eclipse]

I would check the fuse out further. Mine looked fine until I tried pulling it out and it disintegrated in my hand

really? haha-- volt meter set on resistance will solve your issue in .1 seconds

 

[rlacasse1]

So did one little tug on the fuse.

 

[turbo98eclipse]

tugging is a test of resistance .... kind of

 

[CHAMBERHOLE]

Check your tension on alt.belt..also look for a ground that could be knocked off/corroded/loose connections

 

[936DSMboy]

I also think I have the same problem my battery and alt checked out good and yesterday I found out that one of the connections on one of the terminals was loose so I fixed it and now its a waiting game to see if it was actually that

 

[turbo98eclipse]

I have redone ALL grounds, All positives in the car all the way to the damn stereo.

Check your tension on alt.belt..also look for a ground that could be knocked off/corroded/loose connections

as for the OP its 99% apparent that the answer to his problem is the alternator seeing as how it tested so low-- so im not sure who your reply was for... but welcome to the forums!! nice to see you just jump into action

I also think I have the same problem my battery and alt checked out good and yesterday I found out that one of the connections on one of the terminals was loose so I fixed it and now its a waiting game to see if it was actually that

loose terminal can def be the cause.

 

[936DSMboy]

I think it was the loose terminal I started up the car today and it turned on in a breeze