Re: Street strip wiring options
[Re: TC@HP2]
#2629486
03/06/19 03:04 AM
03/06/19 03:04 AM
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Joined: Aug 2003
Posts: 43,157 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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I ran a #10 gauge wire from the 100 amp one wire alternator to the battery side of my battery disconnect switch mounted on the rear taillight panel on my 1970 S/P Cuda, works good, last a long time! I like and use the KISS principle How many amps is your alternator? If more than 120 Amps use a #8 gauge wire from the alternator to the battery connection.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Street strip wiring options
[Re: Cab_Burge]
#2629539
03/06/19 10:29 AM
03/06/19 10:29 AM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Tony -Is this for battery in trunk and kill or disconnect switch in back?
Any additional running equipment? such as electric fuel pumps, fans, efi? This makes a big difference in terms of power distribution location.
Last edited by Mattax; 03/06/19 10:45 AM.
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Re: Street strip wiring options
[Re: Mattax]
#2629599
03/06/19 12:25 PM
03/06/19 12:25 PM
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Joined: May 2008
Posts: 5,399 Aurora, Colorado
451Mopar
master
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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With a one wire alternator, unless I'm missing something, I think it option 2 is too complicated.
If you like the idea of a relay, put it in the engine compartment and arrange it more like alternative #1. Advantages would be much shorter path from power source to equipment (ignition, lights, etc). Alternator to Starter relay stud could be an 8 or 10 gage wire depending on the expected load. It still should get some fusible links in case there is a short before the breakers and fuse box. Probably the best location in this arrangement will be at the starter relay.
I like that configuration.
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Re: Street strip wiring options
[Re: Cab_Burge]
#2629607
03/06/19 12:40 PM
03/06/19 12:40 PM
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Joined: Jan 2003
Posts: 5,388 Pikes Peak Country
TC@HP2
OP
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OP
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Posts: 5,388
Pikes Peak Country
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dvw and tubtar, definietly looking at some higher rated switches other than the generic $40 disconnect switch. There are some pretty high rated units up to 250 amps continouos with 1000 surge.
Cab, my alternator is 50 amps at idle 75 amps at 3000 rpm. That should be the ceiling on it.
Mattax, this a trunk mount battery with disconnect switch. As a street car, yea, I've got a full complement of other functional items in addition to the ignition; all light systems (head, tail, dome, dash, ash, glove, brake, hazard, turn signals), hvac, radio, fuel pumps. May consider O2 sensors or efi in the future as well. Can't foresee ever doing power windows or seats. As a '74, it also has all the seatbelt interlock stuff that I'm working out of the system and replacing with the clutch start circuit. So when you say relay, something capable of the full amp load of the balance of the system plus a margin or the total alt output? In that case, would I still want the power lead from the starter to the OEM relay?
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Re: Street strip wiring options
[Re: TC@HP2]
#2629640
03/06/19 01:47 PM
03/06/19 01:47 PM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Mattax, this a trunk mount battery with disconnect switch.
OK. And I'll assume the switch must also kill the motor, and grounding out the engine is not allowed. As a street car, yea, I've got a full complement of other functional items in addition to the ignition; all light systems (head, tail, dome, dash, ash, glove, brake, hazard, turn signals), hvac, radio, fuel pumps. May consider O2 sensors or efi in the future as well. Can't foresee ever doing power windows or seats. Fuel pump, EFI are the big ones that might benefit from a strategy different than stock. These can draw down the battery when the alternator is not running (start) or not capable of providing the power demanded. Lets say an alternator is used that can produce 280 Watts when the engine is at 650 rpm. This means it can provide up to 20 amps at 14 Volts. I'm not sure what the 'turn on' speed is for a 1-wire, but for sake of example, lets assume its self powering at 650rpm and the field is drawing off 2.5 amps. A solid state ignition maybe draws another 2.5 amps. That leaves 15 amps for everything else. Turn on the lights and that's around 14 amps, Step on the brakes and now the alternator can not supply the power needed. System voltage drops and when it gets around 12.8 Volts, the battery becomes the power source with highest voltage. This was somewhat tolerable with mechanically supplied fuel, since it only happened briefly at stop lights and stop signs. But with more equipment, this is situation will occur more frequently. The typical stock systems through '75 assumed the power would almost always come from the alternator and the battery would only need minor recharging. As a '74, it also has all the seatbelt interlock stuff that I'm working out of the system and replacing with the clutch start circuit. So when you say relay, something capable of the full amp load of the balance of the system plus a margin or the total alt output? In that case, would I still want the power lead from the starter to the OEM relay? Can't help with the interlock. When I say full amp load, I mean the equipment that will be calling for power. I don't know if it makes a difference whether an second wire is run all the way from the cut off switch to the OEM Relay stud, vs connecting it as shown in the drawing. I'll work on a drawing but post this now, as the board may shut soon.
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Re: Street strip wiring options
[Re: Mattax]
#2629696
03/06/19 05:56 PM
03/06/19 05:56 PM
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Joined: Feb 2011
Posts: 1,454 Glendora Ca.
Just-a-dart
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pro stock
Joined: Feb 2011
Posts: 1,454
Glendora Ca.
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There are lots of ways to do this, but for me simple is best. I design systems with short wire lengths where possible to help with voltage drop and weight.
The problem with any relay controlled by the battery disconnect switch is the relay uses power and will kill the battery if left on for long periods of time. The higher the relay current rating the more power it takes to operate normally.
"Just a Bracket car dressed up like a streetcar"
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Re: Street strip wiring options
[Re: Just-a-dart]
#2629737
03/06/19 07:39 PM
03/06/19 07:39 PM
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Joined: Feb 2010
Posts: 1,645 Phila. Pa.
Mattax
top fuel
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top fuel
Joined: Feb 2010
Posts: 1,645
Phila. Pa.
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Good point! The relay would need a second switch in the driver's compartment to be a little more convenient.
Suppose could have a pair of relays, the first connected to ignition Run, that relay then opening or closing the trigger or ground for relay 2. A little more complicated but still seems simpler and cleaner than alternative 2.
Last edited by Mattax; 03/06/19 08:03 PM.
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Re: Street strip wiring options
[Re: Mattax]
#2629938
03/07/19 11:55 AM
03/07/19 11:55 AM
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Joined: Jan 2003
Posts: 5,388 Pikes Peak Country
TC@HP2
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OP
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Posts: 5,388
Pikes Peak Country
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There are lots of ways to do this, but for me simple is best. I design systems with short wire lengths where possible to help with voltage drop and weight.
The problem with any relay controlled by the battery disconnect switch is the relay uses power and will kill the battery if left on for long periods of time. The higher the relay current rating the more power it takes to operate normally. Cool. Care to share any designs? The hand drawn diagram will kill the engine but doesn't completely disconnect the battery. Some of this comes down to what the goals are. isolate the battery? kill the engine? both? The goal is to kill the engine and isolate the battery to meet NHRA, SCCA, and NASA requirements. I figured there are way more NHRA drivers on Moparts who have done this than either SCCA or NASA, so I'm here in the race forum. I have previously done this on a dedicated track car. Amp draw was low and of limited time, so I set it up to run everything off the battery and the alternator feed the battery. This is my first effort in a dual purpose car where there is more power distribution than just ignition and fuel. I figure I will need to have a distribution point near the front of the car for these street items. Running cabin items off distribution directly from the alternator is probably fine, so long as fuel and ignition are shut down with the disconnect switch. My alternator does produce 50 amps at 800 rpm, so I've got decent coverage for draw at stop lights, even if/when EFI is factored in.
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Re: Street strip wiring options
[Re: Mattax]
#2629974
03/07/19 01:19 PM
03/07/19 01:19 PM
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Joined: Jan 2003
Posts: 8,022 Tulsa OK
Bad340fish
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master
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Posts: 8,022
Tulsa OK
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On my street car I took out all the factory stuff for the engine, the factory wiring only runs the lights and wipers.
This is how I wired mine.
Battery to 4 pole disconnect Disconnect to Starter Relay in Trunk-Relay to starter(only hot when cranking) Disconnect to Power Distribution-amp gauge wire goes to this and powers up the lights and wipers.
There is a continuous duty solenoid between the alternator output and my power distribution. That Continuous duty solenoid is powered up by ignition on, however the power runs from ignition on through the small poles on the 4 pole disconnect and back up to the solenoid.
This way when the key is off, the continuous duty solenoid is off, but the master disconnect still kills everything.
That was hard to explain and probably makes no sense lol.
68 Barracuda Formula S 340
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Re: Street strip wiring options
[Re: TC@HP2]
#2629992
03/07/19 01:42 PM
03/07/19 01:42 PM
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Joined: Aug 2003
Posts: 43,157 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,157
Bend,OR USA
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On your deal I would run a #8 or#10 gauge wire from the alternator output directly back the battery side of the cut off switch so the car will not run with the switch in the off position, no volts to the rest of the cars electrical from the alternator in the off position. Make all of your other needed electrical feeds from the battery cable up front to keep the rest of the wiring needed short as possible to reduce resistance and voltage drop. Safe, simple and effective !
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Street strip wiring options
[Re: Cab_Burge]
#2629997
03/07/19 01:56 PM
03/07/19 01:56 PM
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Joined: Jan 2003
Posts: 8,022 Tulsa OK
Bad340fish
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master
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Tulsa OK
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Cab the only thing I don't like about that is the alternator wire is still hot, the car will die but the alt wire will have power.
With loads of accessories on mine Street car stuff(lights wipers), Fuel Injection ECU, Two Fuel Pumps, two fans, electric water pump, and laptop and phone charging on drag week I like to have a sense wire for the alternator to work off of the power distribution point. It complicates the shut off no doubt but I feel it works better in the end.
68 Barracuda Formula S 340
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Re: Street strip wiring options
[Re: challenger1320]
#2630029
03/07/19 03:37 PM
03/07/19 03:37 PM
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Joined: Jan 2012
Posts: 2,645 Stuttgart, Arkansas
rickseeman
master
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master
Joined: Jan 2012
Posts: 2,645
Stuttgart, Arkansas
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Why not put the disconnect on the ground side. That's against the rules and you don't want it that way anyhow. My buddy had a car like that and it would blow your mind. Crazy stuff like, when you turned off the disconnect, the brake lights would come on. It would drive you absolutely crazy.
2011 Drag Pak Challenger
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