Voltage Drop When The Car Comes 2 A Stop

[Truconcept 58]

Hi

99 Oldsmobile Alero

Yellow optima up front and one in the rear

Powerbastards 220amp alt

knu 1/0gauge (+ and -) front to back, big3

as of today. no fuses. problem persists

Im getting a drop from 14.4 to as low as 13.2 when I bring the car to a stop

Sometimes it stays at 14.4 when I stop but most of time it dont

13.2 is about as low as it gets, its random and sometimes doesnt drop at all

I only get this reading from the rear battery

I dont have any of my amps connected, no sound, still a drop

The rear battery is grounded to the negative in the front

I have also tried grounding the rear battery to the point

under the seatbelt bolt that i have used before (no luck)

The front battery is grounded to some metal thing thats bolted to the side of the engine

Im sorry I cant be more specific

The mechanics who put my alternator on made that the front batt negative ground

They are good so Im gonna assume thats a legit spot

When I start the car I get a 15-15.2V reading but Im just assuming

thats from the freezing weather reducing resistance

Any ideas?

Edited February 6, 2013 by Truconcept

[Julian 641]

When your Alt RPMS drop your voltage will drop too. Only thing you really can do is either hold RPMS to raise you voltage while stopped. Sounds like you might need a slightly smaller pulley because the turn on RPM for that alt is probably around 1000-1500 rpm

[Truconcept 58]

Im starting to think about putting the factory alternator back in

I was always 14.4v idle with no music on

I just find it odd theres a drop on the back battery

but not on the front

maybe i should only worry if it goes under 12v on music?

Edited February 6, 2013 by Truconcept

[Julian 641]

If there is a big drop between the front and back more than a .5v I would check all of my connections, and ensure that nothing is grounding out.

[EPerez 236]

I don't think I can help you other than say check all the connections, which was already stated by Julian. I saw that your update said you bought this used from a guy. Maybe that could be the problem? I'm not sure, but maybe it might help someone else help you figure out your voltage drop.

[nervewrecker 0]

Disconnect the rear batt and leave it to stand alone for a few hours, see what the resting voltage is.

Sounds like a damaged cell to me.

[nervewrecker 0]

I'm just curious about the alternator ground too, stock? Is it clean?

[djjdnap 78]

13.2 isn't low at all

with my heat on my truck drops to 12.x

HO alts suck at low rpms, but 13v is nothing to be worried about.

get a smaller pulley to fix the problem, unless your car is pcm controlled alt, then you have to go buy some other stuff, but figure that out first and we can go from there.

[Jason Witt 65]

Disconnect the rear batt and leave it to stand alone for a few hours, see what the resting voltage is.

Sounds like a damaged cell to me.

x2

[DanP 19]

Disconnect the rear batt and leave it to stand alone for a few hours, see what the resting voltage is.

Sounds like a damaged cell to me.

x2

Brutal was just about to send you a PM with this thread, telling you to help your friend.

[nadcicle 77]

Hi 99 Oldsmobile Alero Yellow optima up front and one in the rear Powerbastards 220amp alt knu 1/0gauge (+ and -) front to back, big3 as of today. no fuses. problem persists Im getting a drop from 14.4 to as low as 13.2 when I bring the car to a stop Sometimes it stays at 14.4 when I stop but most of time it dont 13.2 is about as low as it gets, its random and sometimes doesnt drop at all I only get this reading from the rear battery I dont have any of my amps connected, no sound, still a drop The rear battery is grounded to the negative in the front I have also tried grounding the rear battery to the point under the seatbelt bolt that i have used before (no luck) The front battery is grounded to some metal thing thats bolted to the side of the engine Im sorry I cant be more specific The mechanics who put my alternator on made that the front batt negative ground They are good so Im gonna assume thats a legit spot When I start the car I get a 15-15.2V reading but Im just assuming thats from the freezing weather reducing resistance Any ideas?

When you say " at the rear battery " what is your method of measurement? Do you have a meter ran all the way to your rear battery and a separate one running to your front battery or alternator at the same time? I am curious because I had two of the exact model stingers before that gave different voltages out of the box and needed to be calibrated before use. I just find it weird that you are dropping voltage without any draw. I am x2 on this being a bad battery in the back if it is only happening in the back. I would charge it fully then toss it back on there. The other thing I would check is the fuse in between the front and back battery. I have seen rattles and bumps cause these to come loose at the fuse or the connection.

[DanP 19]

Hi 99 Oldsmobile Alero Yellow optima up front and one in the rear Powerbastards 220amp alt knu 1/0gauge (+ and -) front to back, big3 as of today. no fuses. problem persists Im getting a drop from 14.4 to as low as 13.2 when I bring the car to a stop Sometimes it stays at 14.4 when I stop but most of time it dont 13.2 is about as low as it gets, its random and sometimes doesnt drop at all I only get this reading from the rear battery I dont have any of my amps connected, no sound, still a drop The rear battery is grounded to the negative in the front I have also tried grounding the rear battery to the point under the seatbelt bolt that i have used before (no luck) The front battery is grounded to some metal thing thats bolted to the side of the engine Im sorry I cant be more specific The mechanics who put my alternator on made that the front batt negative ground They are good so Im gonna assume thats a legit spot When I start the car I get a 15-15.2V reading but Im just assuming thats from the freezing weather reducing resistance Any ideas?

When you say " at the rear battery " what is your method of measurement? Do you have a meter ran all the way to your rear battery and a separate one running to your front battery or alternator at the same time? I am curious because I had two of the exact model stingers before that gave different voltages out of the box and needed to be calibrated before use. I just find it weird that you are dropping voltage without any draw. I am x2 on this being a bad battery in the back if it is only happening in the back. I would charge it fully then toss it back on there. The other thing I would check is the fuse in between the front and back battery. I have seen rattles and bumps cause these to come loose at the fuse or the connection.

He said he uses no fuses, but this is also the kid who said his daddy has a viper in chat. Not to mention he said he was 15 so why exactly is he driving.

[jonbearsmt 919]

sounds normal to me for an after market alt.. if you throw your car in nutrel while at a light im sure it comes back up to 14

[Truconcept 58]

The problem is actually the alternator thanks guys

I have put my old alt back in and now rest comfortably at 14.4

Idk if the h/o alt is bad at low rpm, as mentioned

either way 13.2 idle without music at a stop sign is no good 4 me

He said he uses no fuses, but this is also the kid who said his daddy has a viper in chat. Not to mention he said he was 15 so why exactly is he driving.

LMAO!

p.s- yea i took the fuses out to eliminate them as the possible cause of the drop

[Dictator 39]

Who plays it loud.... At stop lights and stop signs. Suppose to turn it down for respect.

[Truconcept 58]

Who plays it loud.... At stop lights and stop signs. Suppose to turn it down for respect.

im not that loud lol

[nadcicle 77]

The problem is actually the alternator thanks guys I have put my old alt back in and now rest comfortably at 14.4 Idk if the h/o alt is bad at low rpm, as mentioned either way 13.2 idle without music at a stop sign is no good 4 me

He said he uses no fuses, but this is also the kid who said his daddy has a viper in chat. Not to mention he said he was 15 so why exactly is he driving.

LMAO! p.s- yea i took the fuses out to eliminate them as the possible cause of the drop

All this means is you need to change out your alternator pulley to a smaller pulley for higher voltage at idle. My replacement HO alt has no issues whatsoever with idle voltage. I cold start at 15.4 and it works its way down to 14.4 - 14.6 and only goes below that if I let me music keep going while at a stop sign. I can put my foot on the gas and visually see that it comes right back up to 14.4-14.6 when I match rpm to alt output level. The lowest i see it drop is around 13.8 full tilt. I honestly would give the alternator more of a chance when you have a good load to it between 1200 to 1500 rpm because that is where HO alternators are measured.

[jonbearsmt 919]

like i said it sounds like all High outputs... they are made to put out max power at around 1800 RMps, because you should always idle up to put a load on... because of cooling.

you need a smaller pulley and maybe raise your TB idle up.

AMPS are what you really need... and your factory puts out way less amps. IMO

[Dictator 39]

like i said it sounds like all High outputs... they are made to put out max power at around 1800 RMps, because you should always idle up to put a load on... because of cooling.

More power and more power ftw!!

you need a smaller pulley and maybe raise your TB idle up.

AMPS are what you really need... and your factory puts out way less amps. IMO

[jonbearsmt 919]

you posted with no reply

[bassahaulic 155]

What's happening is when you come to a stop and your idle drops, the alternator is no longer spinning fast enough to field so it in effect, turns off.

A smaller pulley should fix that.

P.S.

Powerbastards alts are awful. lol

Edited February 10, 2013 by bassahaulic

[shizzzon 461]

Another thing too-

Even it the alt is on and outputting current, if it's "rewound" all shitty, then it will exhibit idle output worse or equal to your stock alternator.

And if so, that would mean normal to average current draw for daily driving would bog it down at idle rpm causing the voltage to sag because it's at maximum potential at idle rpm.

Getting a smaller pulley would, if needed, fix the turn on output of the alternator by spinning faster at lower engine rpm but if it's rewound, then nothing will fix that except for throwing it in the trash.

[Dictator 39]

How would you know if you have a rewound alternator?

[shizzzon 461]

Well, an ammeter would definitely show you that.

 

In my experience, correct me if i'm wrong, but rewound, to me, means substantial higher output at whatever engine rpm is required but the idle is reduced compared to STOCK or of equal value to stock.

 

High outputs bought from reputable companies like DC, Mechman(when they use the right pulleys) and Singer, have large idle outputs like it should be.

 

IE rewound-  

Saying you have a 250A alt cold, 210A hot but only 60A idle COLD, maybe 30A hot.

[Truconcept 58]

ive lurked on a few car audio forums

and never read about these wound alts barely putting out anything @ idle

of course i find out after i buy one

fail.