Voltage question
06-07-2004, 12:02 PM
#1
Drifting
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Voltage question
Well I don't think this is a problem, more of a making sure thing. Since I put my Iceshark light kit in a few weeks ago I noticed my voltage guage now showing the needle up on the 14 instead of in between the 12 and 14 like it used to be. I assume this is because of the new voltage regulator on the alternator being 14.4v instead of 14v. So I assume this is normal, but knowing me I find every little thing that's out of the ordinary on my car and investigate it so I figured I may as well make sure I didn't hook something up wrong. Kinda funny that I'm an electrical engineering student and don't already know the answer to this. Then again I'm only starting my 3rd year and have yet to take anything very technical.
On another note it's so good to have this thing on the road again. Went out for a nice drive this morning....since I've been driving my Mustang around so much I'd forgotten just how much more refined and pleasurable this car is to drive. Even when I start driving the Mustang daily again I'm going to make sure I get this one out more often. It seems like the more you run these cars (and harder you run them) the better they seem to run. You can almost hear the car begging you not to back off once you get north of 4k rpms
On another note it's so good to have this thing on the road again. Went out for a nice drive this morning....since I've been driving my Mustang around so much I'd forgotten just how much more refined and pleasurable this car is to drive. Even when I start driving the Mustang daily again I'm going to make sure I get this one out more often. It seems like the more you run these cars (and harder you run them) the better they seem to run. You can almost hear the car begging you not to back off once you get north of 4k rpms
06-07-2004, 12:47 PM
#2
Nordschleife Master
14.0v on the inside gauge is what you want to see! 
Two major things are going on to get you up there.
Wiring: you have the additional ground from the front of the motor to frame rail - this really helps a lot, much more than one would first suspect. Also the headlight load is now off the stock electrical system so you don't have the resistance voltage losses that occur as electricity to power the headlights runs from the alternator to the battery and then over and through the fuse/relay board. When the headlights used to suck juice through the relay board they knocked down the whole system.
Regulator at 14.4v: The regulator sets the maximum voltage ceiling the alternator will put out. However, our alternators can't put out 14.4v once the load reaches about 40 amps. But under that level the alternator will put out 14.4v. This charges up the battery quicker so you don't have as much of that load on the system. You also can afford to lose some voltage through resistance as the juice travels over to the fuse/relay board. In your case you are losing 0.4v through the stock wiring under minimal electrical draw. That is why I pull the power directly off the alternator for the lighting harness so the lights don't have to lose juice through the stock wiring. Before I built the prototype harness I was down to 10.4 volts at the headlights through the stock system. That is a LOT! If you now measure voltage at the headlight bulbs you will find you are getting almost the full 14.4v (like 14.3 ) - there are some minor losses when the current runs through the fuse and relay but not much to speak of.
Anyway, you are just fine with your readings.
Two major things are going on to get you up there.
Wiring: you have the additional ground from the front of the motor to frame rail - this really helps a lot, much more than one would first suspect. Also the headlight load is now off the stock electrical system so you don't have the resistance voltage losses that occur as electricity to power the headlights runs from the alternator to the battery and then over and through the fuse/relay board. When the headlights used to suck juice through the relay board they knocked down the whole system.
Regulator at 14.4v: The regulator sets the maximum voltage ceiling the alternator will put out. However, our alternators can't put out 14.4v once the load reaches about 40 amps. But under that level the alternator will put out 14.4v. This charges up the battery quicker so you don't have as much of that load on the system. You also can afford to lose some voltage through resistance as the juice travels over to the fuse/relay board. In your case you are losing 0.4v through the stock wiring under minimal electrical draw. That is why I pull the power directly off the alternator for the lighting harness so the lights don't have to lose juice through the stock wiring. Before I built the prototype harness I was down to 10.4 volts at the headlights through the stock system. That is a LOT! If you now measure voltage at the headlight bulbs you will find you are getting almost the full 14.4v (like 14.3 ) - there are some minor losses when the current runs through the fuse and relay but not much to speak of.
Anyway, you are just fine with your readings.
Last edited by IceShark; 06-07-2004 at 01:03 PM.
06-07-2004, 12:59 PM
#3
Drifting
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Thanks Dan! Your kit does quite a few good things to the electrical systems of these cars. My guage lights are brighter now, and things just seem to work a little smoother now. And the lighting...I was riding next to my cousin's '04 BMW 325 with the xenon lights and mine were just as good (maybe even a little better). I was in a parking lot next to my brother who has H4s in his '84 and you couldn't even tell his lights were on with me next to him. I'm sure he's gonna want these soon too
An excellent alternative to the cost of an HID kit!
An excellent alternative to the cost of an HID kit!
06-08-2004, 04:49 AM
#4
Race Director
Is there any worry on cooking the battery above 13.8v??? I noticed too that with my adjustable VRM set to about 13.5v during the day, it drops to about 12.5v at night with the lights on. Alternator starting to go south?
06-08-2004, 12:23 PM
#5
Nordschleife Master
No, Danno, on cooking the battery at these levels of 14.4v out of the alternator and 13.9 to 14.0 at the battery posts. Our battery is isolated from the engine bay heat and is just fine. I'm in MN so having a fully charged battery for starting in the winter is a really big deal. Shops here are setting regulators at 14.9v to get the battery topped off quicker and there is no apparent rush to replace cooked batteries.
As far as your drop in voltage, what do you actually have the VR set to with a measurement off the alternator itself rather than taking off the battery? I know this is about impossible to do with a turbo unless you pull things apart to attach a test lead to the Pos post. But you pull whole motors in an hour and think nothing of it.
One full volt drop at night, when it should be cooler, tells me that you probably have bad wiring that is leaking like crazy when you add another 20 amp draw for all the lights. The alternator may be going south but I would suspect the wiring first. Our alts can hold 14.4v until about 40 amps. Also, to the cooking issue, the voltage regulator will scale back output as heat soars. Down from 14.4v to ~ 13.75 if you were in Death Valley at 13:00. Not enough and right circumstances to explain your drop.
Soooo, I would start poking around and add a supplemental ground or two and clean up the terminals. I think you are seeing resistance losses. If you haven't done anything with the grounds I can send you one of the ground upgrade packages and you can see what happens.
As far as your drop in voltage, what do you actually have the VR set to with a measurement off the alternator itself rather than taking off the battery? I know this is about impossible to do with a turbo unless you pull things apart to attach a test lead to the Pos post. But you pull whole motors in an hour and think nothing of it.
One full volt drop at night, when it should be cooler, tells me that you probably have bad wiring that is leaking like crazy when you add another 20 amp draw for all the lights. The alternator may be going south but I would suspect the wiring first. Our alts can hold 14.4v until about 40 amps. Also, to the cooking issue, the voltage regulator will scale back output as heat soars. Down from 14.4v to ~ 13.75 if you were in Death Valley at 13:00. Not enough and right circumstances to explain your drop.
Soooo, I would start poking around and add a supplemental ground or two and clean up the terminals. I think you are seeing resistance losses. If you haven't done anything with the grounds I can send you one of the ground upgrade packages and you can see what happens.
