Can't keep my voltage up......
03-03-2007, 09:56 AM
#1
Can't keep my voltage up...... I swear my electrical system needs Viagra, because I can't get the voltage to stay up!
It was fine before the 408/D1SC install when it was just a H/C car, but since the install of the motor, blower, and requisite supporting hardware (fans, ewp, big fuel pump, etc.) my voltage drops pretty bad once warmed up. I purchased a larger alternator from Afterthoughts Auto, and it did increase voltage when I first start the car, but after a few miles of driving the voltage drops pretty low at idle, like 12.0. And its cold here, its only gonna get worse as it gets warmer out.
All I am running is the stock ATI fan plus a 9 inch puller Spal, an EWP, a magnafuel 750 pump, and the ecm. I really think it should keep up better. Its not like I have a big stereo or something.
I guess the only thing left to try is a bigger battery. I currently use a Odyssey 650, the little one. I might go get a yellow Optima, but I'll end up relocating that to the back because this pigs heavy anyway and all it needs is even more weight up front.
Any thoughts? I can hear the FP pulsating at idle with the voltage drop and its surely not helping my cooling issues.
It was fine before the 408/D1SC install when it was just a H/C car, but since the install of the motor, blower, and requisite supporting hardware (fans, ewp, big fuel pump, etc.) my voltage drops pretty bad once warmed up. I purchased a larger alternator from Afterthoughts Auto, and it did increase voltage when I first start the car, but after a few miles of driving the voltage drops pretty low at idle, like 12.0. And its cold here, its only gonna get worse as it gets warmer out.
All I am running is the stock ATI fan plus a 9 inch puller Spal, an EWP, a magnafuel 750 pump, and the ecm. I really think it should keep up better. Its not like I have a big stereo or something.
I guess the only thing left to try is a bigger battery. I currently use a Odyssey 650, the little one. I might go get a yellow Optima, but I'll end up relocating that to the back because this pigs heavy anyway and all it needs is even more weight up front.
Any thoughts? I can hear the FP pulsating at idle with the voltage drop and its surely not helping my cooling issues.
03-03-2007, 10:17 PM
#4
With that little battery you are just running off the alternator mostly.
Went through the same crap, big battery in the trunk, 145A alternator and a voltblaster. Its rough with an EWP and that big FP running plus a few fans. Then you have what the PCM/BCM takes, wideband, daytime running lights etc.
My car at idle draws nearly 100 amps with the fan on (I have a single 16"), its crazy.
Went through the same crap, big battery in the trunk, 145A alternator and a voltblaster. Its rough with an EWP and that big FP running plus a few fans. Then you have what the PCM/BCM takes, wideband, daytime running lights etc.
My car at idle draws nearly 100 amps with the fan on (I have a single 16"), its crazy.
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03-04-2007, 11:24 AM
#9
Originally Posted by kp
No, you are screwed with the small battery.
Take the weight hit and try a big battery, put it in the back and add another 20lbs in cables and box so I would leave it up front.
Mine is OK but you have more stuff going then I do..
Take the weight hit and try a big battery, put it in the back and add another 20lbs in cables and box so I would leave it up front.
Mine is OK but you have more stuff going then I do..
I think the only thing I have running that you don't is the 9" Spal puller fan. Otherwise, we both have the EWP, 16" fan, big fuel pump, and ecm. I have the stock radio and I do use it but it can't draw that much power. I even killed my DRL's.
I don't think I will ever get to use my A/C, I always thought the overheating would keep me from using it but I won't even have the power to use it.
03-04-2007, 11:37 AM
#11
Street driving is a little tougher, I dont drive mine anymore but most likely yours is about the same as mine.
You are going to lose some with the relocated battery too, voltage drop from all that cable sucks as well.
They say the EWP draws 13amps and the magnafuel pump is 10 amps but I get 18 and 20 amps lol. Plus the BS3 has a pretty hot spark and I'm sure that thing running is in the 30-40 amp range, plus the stock PCM still does a few things, plus I have two widebands, ~ 7amps each, I stopped the DRLs a while back but the brake lights, whatever the BCM is doing is even a few more amps.
Sometimes I think my alternator sucks as much horsepower as the blower
You are going to lose some with the relocated battery too, voltage drop from all that cable sucks as well.
They say the EWP draws 13amps and the magnafuel pump is 10 amps but I get 18 and 20 amps lol. Plus the BS3 has a pretty hot spark and I'm sure that thing running is in the 30-40 amp range, plus the stock PCM still does a few things, plus I have two widebands, ~ 7amps each, I stopped the DRLs a while back but the brake lights, whatever the BCM is doing is even a few more amps.
Sometimes I think my alternator sucks as much horsepower as the blower
03-04-2007, 07:59 PM
#12
I don't understand why this car in particular is having so much trouble? My GN had the FAST ecm, 2 big fans, power everything, decent fuel pumps, and a big stereo and I actually used the A/C in it. The stock alternator never had a problem keeping up.
So should I get the bigger battery or no? If its not gonna fix it I don't wanna waste the $$$.
So should I get the bigger battery or no? If its not gonna fix it I don't wanna waste the $$$.
03-06-2007, 10:33 AM
#16
Try spinning the alt. faster......
I have a 105amp alt on my race car. Pulleys are 2.5" alt. and 6" crank I think. Running a digital 7 box, HVC2 coil, twin SPAL 14" fans, EWP, wideband, and Magnafuel 500 pump. Idles at 1200rpm and has over 14.5 volts.
Are you sure you don't have a wiring issue from the alt. to the battery? Too small gauge wire maybe? I don't care what battery you have, that should only be needed to start the car. IMO, after that, everything should run off the alt. power.
Craig
I have a 105amp alt on my race car. Pulleys are 2.5" alt. and 6" crank I think. Running a digital 7 box, HVC2 coil, twin SPAL 14" fans, EWP, wideband, and Magnafuel 500 pump. Idles at 1200rpm and has over 14.5 volts.
Are you sure you don't have a wiring issue from the alt. to the battery? Too small gauge wire maybe? I don't care what battery you have, that should only be needed to start the car. IMO, after that, everything should run off the alt. power.
Craig
03-06-2007, 11:24 AM
#18
You can try a smaller pulley but they dont do much, if you have a car that is street driven and idles a lot you NEED a big battery if the car at idle draws more then the alternator can put out. Those little batteries have almost no reserve capacity at all.
An alternators output is rated cold, as it warms up current output can drop up to 75%. These cars draw a lot of current, couple heated narrowband O2s, 'street' EWPs that draw a lot of current, 60psi huge fuel pump, BCM, PCM, wideband, lights, stereo. I actually measured mine with an inductive amp probe because I couldnt see why the (big) battery kept going dead at the track after like 3 passes and cooling off with the EWP/fan for a few minutes.
Simple math, stock alternator put out 60 amps hot, car draws 100 amps running = drawing 40 amps from the battery whenever the car is running. Plus add another 40 amps for 5 minutes cooling it off and no battery can take that. The 145a alt I have will put out 100 amps hot and I can pretty much do a whole day (6-8 passes) without charging the battery - thats acceptable to me. On the street its no problem either, battery has plenty of reserve to sit and idle at 750rpm for a good amount of time.
Also make sure and check you voltage at the battery with a decent voltmeter, my stock volt gauge in the car reads 2 volts low.
An alternators output is rated cold, as it warms up current output can drop up to 75%. These cars draw a lot of current, couple heated narrowband O2s, 'street' EWPs that draw a lot of current, 60psi huge fuel pump, BCM, PCM, wideband, lights, stereo. I actually measured mine with an inductive amp probe because I couldnt see why the (big) battery kept going dead at the track after like 3 passes and cooling off with the EWP/fan for a few minutes.
Simple math, stock alternator put out 60 amps hot, car draws 100 amps running = drawing 40 amps from the battery whenever the car is running. Plus add another 40 amps for 5 minutes cooling it off and no battery can take that. The 145a alt I have will put out 100 amps hot and I can pretty much do a whole day (6-8 passes) without charging the battery - thats acceptable to me. On the street its no problem either, battery has plenty of reserve to sit and idle at 750rpm for a good amount of time.
Also make sure and check you voltage at the battery with a decent voltmeter, my stock volt gauge in the car reads 2 volts low.
03-06-2007, 11:52 AM
#19
Don't think that "IMO, after that, everything should run off the alt. power."
is true.
The alternator is designed to replenish the battery charge after starting is done.
2 things they don't do well:
1. Act a charger should the battery go dead.[IE: After a jump start.]
2. Run under full load for extended periods of time.
Some things, [ may have already been mentioned], are:
Defective/insufficient wiring.
Bad grounds, loose connections.
Slipping belt.
Insufficient battery capacity.
" " alt " ".
Battery with bad cell[s].
Battery not fully charged. [Special charger needed for some AGM batteries.]
Alt with the diode bridge blown.
is true.
The alternator is designed to replenish the battery charge after starting is done.
2 things they don't do well:
1. Act a charger should the battery go dead.[IE: After a jump start.]
2. Run under full load for extended periods of time.
Some things, [ may have already been mentioned], are:
Defective/insufficient wiring.
Bad grounds, loose connections.
Slipping belt.
Insufficient battery capacity.
" " alt " ".
Battery with bad cell[s].
Battery not fully charged. [Special charger needed for some AGM batteries.]
Alt with the diode bridge blown.
03-06-2007, 07:35 PM
#20
Well, its a new alternator and the stock alternator did it too. I think I may try a smaller alternator pulley (even with the bigger battery), since the voltage goes up pretty quick when you're on the gas. I idle around 800 rpm, and I'm on the stock crank pulley. I don't see any other wiring issues, but I'll double check. I'm measuring the voltage with the stock gauge and a scan tool, but I can use my meter to verify. I don't doubt its dropping though, you can hear the FP pulsing.
Maybe you guys can settle an argument for me? My buddy says that the reason the voltage is higher on cold startup is because the alternator senses the battery capacity is low (from starting the car) and puts out higher power to charge the battery. He says the voltage drops after running awhile because the battery has been charged and the demand on the electrical system is lower. I say the voltage is higher on cold start because the alternator is cold, and they lose capacity as they get hot.
Who's right? I think he's nuts, but he's a mechanic and I'm not.
Maybe you guys can settle an argument for me? My buddy says that the reason the voltage is higher on cold startup is because the alternator senses the battery capacity is low (from starting the car) and puts out higher power to charge the battery. He says the voltage drops after running awhile because the battery has been charged and the demand on the electrical system is lower. I say the voltage is higher on cold start because the alternator is cold, and they lose capacity as they get hot.
Who's right? I think he's nuts, but he's a mechanic and I'm not.