Hot Rod Forum : Hotrodders Bulletin Board - Reply to Topic
Hotrodders.com -- Hot Rod Forum



Register FAQ Search Today's Posts Unanswered Posts Auto Escrow Insurance Auto Loans
Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Electrical> Question on where to pick up power for electric fan & headlights.
User Name
Password
lost password?   |   register now

Thread: Question on where to pick up power for electric fan & headlights. Reply to Thread
Title:
  
Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :

Register Now

In order to be able to post messages on the Hot Rod Forum : Hotrodders Bulletin Board forums, you must first register.
Please enter your desired user name (usually not your first and last name), your email address and other required details in the form below.
User Name:
If you do not want to register, fill this field only and the name will be used as user name for your post.
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Additional Options
Miscellaneous Options

Topic Review (Newest First)
08-25-2012 02:28 PM
toddalin
Quote:
Originally Posted by JeffB View Post
There is something that a lot of folks miss and that is the use of relays when doing a rewire this explains it well: Custom Cars Classic Hotrods Streetrods-Watsons StreetWorks Here in the archives of hotrodders.com are many articles by the late Doc. Vette who helped me out a while back.Two places you never want to run without a relay is an electric fuel pump and an electric fan(these draw a large amp load),a common complaint with older cars is dim headlights even though they have been halogen upgraded.I added the relays as per the link and WOW! major lighting improvement!
I had put halogen bulbs in my '64 Corvette years ago and while it helped, it wasn't all that impressive.

About a month ago, I did the headlight relay conversion. I run a 1-wire alternator, so I hid the new headlight relays in the old voltage regulator casing. Note that in GM fashion, this taps off the horn relay that receives its current directly from the alternator.

Using the photometer in my Nikon, I estimate that this conversion made the low beams 100% brighter and the high beams 66% brighter. Others report similar increases. This also takes a load off of your dash lights and they too get brighter.



08-25-2012 02:07 PM
JeffB There is something that a lot of folks miss and that is the use of relays when doing a rewire this explains it well: Custom Cars Classic Hotrods Streetrods-Watsons StreetWorks Here in the archives of hotrodders.com are many articles by the late Doc. Vette who helped me out a while back.Two places you never want to run without a relay is an electric fuel pump and an electric fan(these draw a large amp load),a common complaint with older cars is dim headlights even though they have been halogen upgraded.I added the relays as per the link and WOW! major lighting improvement!
08-24-2012 01:55 PM
russ69coupe Funny, I was just reading this Catalog last night.
It is worth the read. Mark at MAD Electrical really knows his stuff.
hth,
Russ
08-23-2012 11:08 AM
toddalin
Quote:
Originally Posted by grobb284 View Post
II am thinking of adding the switched power of the headlight relay to be picked up from this same power lead for the coolant fan, ie. a power lead from the alternator to a second fused relay panel at the front of the vehicle, for the coolant fan and headlights. This would take a large load off the initial fuse panel.

Take your power off the "always hot" horn relay contact. That's where GM used to do it.
08-22-2012 07:50 PM
astroracer Put in a distribution block just like this...
Catalog
and you will be golden... Very simple. Pull your power from the alternator just as you were planning.
08-22-2012 05:40 PM
grobb284 Not trying to cause a row, but I really don't see the common lines being any more that a buss, that is why I originally posted this topic.

How does the item know where it is at on the buss, it doesn't usually except for negligible resistance of the buss? If you draw a line (buss) and tap off for the battery, the starter solenoid, the alternator, and the take off for the fuse block, and then subsequently drew another line with a mix up of the location of the take offs, how would the buss be any different electrically?
08-22-2012 03:14 PM
RatPin Well to follow up on this I contacted Bob at Rebelwire and learned that my harness was mislabeled. Apperantly someone installed an "Alternator +" lead where they should have put a "Solenoid +" lead. What this means is I have to spend time re routing my harness this weekend. It's a pain because I maticulously group, wrap and shrinktube all my wires at exact lengths so I will need to cut the wire out to re route. To make things more difficult I use high end adhesive lined shrink tubing on many of the wre groups. Not easily removed.

This is kind of a PITA. I did much research before buying my wiring kit and I had heard so many good things and not a single knock aganst rebelwire. Well, here's the first knock against them.
08-21-2012 07:53 PM
RatPin
Quote:
Originally Posted by T-bucket23 View Post
and you should never connect anything directly to the alternator.
Not to dig up an old thread but,

The new wire kit I just installed came with wiring to run a 10g jumper with fusible link from the starter solenoid post to the battery lug on the alternator. From there another 10g lead goes from the alternatorlug to supply power to my main fuse panel in the cab of the vehicle. Are you saying running the power wire from the alt to my fuse panel is wrong?

By the way it is a rebelwire 9+3 kit.
12-27-2011 07:55 PM
bad436z28
coolant fan

why dont u just run a wire from the wiper ignition hot lead to a relay then to ur fans ur making this more complicated than it is.u can also use that for ur headlights.then u can run a switch in ur car also to run the fan,thats what i did.
12-27-2011 04:07 PM
T-bucket23
Quote:
Originally Posted by grobb284
Pretty sure that if it takes 16 volts at the alternator to get to the battery with 14 volts something is indeed wrong. I'm willing to stand by that. Something is wrong for a 2 volt drop, should be always be definitely less than 5% (or even better 3%) of applied voltage.

Also stand by this: The voltage drop to the battery from the alternator will surely be less than 1/2 volt. (less than 3%)



Pretty sure that they are both correct, and follow with current flow, with properly sized cable and adequate components. The alternator would indeed be producing a higher voltage than the battery.

Sorry if I didn't explain this in a better fashion in my earlier post.
Voltage drop will be minimal with properly sized cables. It certainly should not exceed .2-.4 volts. To answer the original question the connections should be as close to the battery as possible and you should never connect anything directly to the alternator. In a trunk mounted battery a good distribution block is essential.
12-27-2011 02:58 PM
grobb284
Quote:
Originally Posted by DanielC

I am going to politely suggest that you do not understand voltage drop, if you cannot understand why you would need an alternator to put out more voltage than you get at the battery with current flowing.

Pretty sure that if it takes 16 volts at the alternator to get to the battery with 14 volts something is indeed wrong. I'm willing to stand by that. Something is wrong for a 2 volt drop, should be always be definitely less than 5% (or even better 3%) of applied voltage.

Also stand by this: The voltage drop to the battery from the alternator will surely be less than 1/2 volt. (less than 3%)


Pretty sure that they are both correct, and follow with current flow, with properly sized cable and adequate components. The alternator would indeed be producing a higher voltage than the battery.

Sorry if I didn't explain this in a better fashion in my earlier post.
12-27-2011 01:59 PM
DanielC "I understand voltage drops."

"If you have to output 16 volts to get 14 to the battery, something is wrong. Not sure why you are bringing that up."

I am going to politely suggest that you do not understand voltage drop, if you cannot understand why you would need an alternator to put out more voltage than you get at the battery with current flowing.
12-27-2011 12:30 PM
grobb284 Not sure where everyone is going with this.

The alternator supplies all the voltage when the vehicle is running, as well as sufficient to charge the battery.

If you have to output 16 volts to get 14 to the battery, something is wrong. Not sure why you are bringing that up.

It is a 3 wire alternator, so I can put the sense point anywhere.

I understand voltage drops. That's why it makes more sense to run the coolant fan/headlights from the alternator, rather than from the battery at the rear. When the car is running, the alternator is the voltage source, not the battery. The voltage drop to the battery from the alternator will surely be less than 1/2 volt.


Please explain why it is better to run the front fuse block from the battery, rather than from the alternator, when all 3 items are in parallel. How would it be different?
12-27-2011 11:17 AM
DanielC What kind of alternator are you using? How is it wired? Is it a GM "single wire"?

The most important function of the alternator is to keep the battery charged. If the battery is dead, you cannot start the car, so cooling the engine becomes unnecessary, and if you are not driving the car, you do not need headlights.

OK, you knew that already.

With a remote battery, the issue become getting the right voltage and current to the battery, in the trunk. Every wire has resistance, even 4-0 gauge cable. The alternator has to put out more voltage than the "ideal" voltage needed at the battery to charge the battery. Depending on the wire (or cable size) the alternator may need to have around 15 or 16 volts AT THE B+ TERMINAL ON THE ALTERNATOR to get 14 volts at the battery. This is called voltage drop. Consider the ground side of the alternator wiring also. Especially with the trunk mounted battery.
One thing people do not realize the battery also functions to regulate the voltage, for a while. When the battery is electrically close to the alternator, the battery is able to better control, or damp any voltage spikes made by the alternator. With a remote battery the voltage at the alternator will vary more. it you start the car, and drive it at night, I could see a situation where the alternator is trying to charge the battery, and puts out 15+ volts to bring the battery up to charge, and you are also running the excess voltage straight to the headlights. They will be really bright. For a short period of time.

If you are using a "one wire" alternator, the alternator does not really know what the battery voltage. The internal regulator only knows the voltage at the B+ terminal of the alternator. Your battery will be most likely be slightly undercharged.

When you are done with wiring your car, you will need to check the voltage drops in the charging circuit, and probably the starting circuit. It would be a good idea to check what the voltage is at the headlights, also
Here is a web page that explains checking voltage drops much better than I could, and it is already done.
http://www.vernco.com/Sparks/id606.htm
12-27-2011 07:24 AM
grobb284 vicrod,thank you for your response. You are correct in what you are saying. However what you described is not what is proposed.

There would be two wires, one running from the alternator to the starter solenoid to act as the battery charge (and feed for the primary fuse block), and a second wire from the alternator to the fuse/relay block at the front of the car for the coolant fan/headlights. There would be two wires, each #8. Overcurrent protection could be fuses, or fusible link.
This thread has more than 15 replies. Click here to review the whole thread.

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -6. The time now is 03:53 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
Copyright Hotrodders.com 1999 - 2012. All Rights Reserved.