Battery Relocation - LS1 Alternator cutoff
11-13-2011, 10:11 PM
#1
Battery Relocation - LS1 Alternator cutoff
I posted this in LS1tech as well, but am hoping for a better response here.
In relocating my battery to the rear, I am sorting out how I will cutoff the alternator power when the cutoff switch is in the Off position.
With the NHRA ruling identifying that the battery switch needs to cutoff all power, I am wondering if the alternator power to the battery can be cutoff in a different manner than the diagram I found on tech.
In thinking out of the box, instead of bringing a #2 cable from the alternator, back to the battery side of the cutoff switch, I am thinking of going a different route, but need some more knowledgeable input before I proceed.
As the LS1 alternator has a "Generator Turn ON Signal" (R15 output from the PCM) to enable the alternator output charging, can this input to the alternator also be used to disable the alternator output? If it can be used without damaging the alternator or PCM, here is my idea.
Install a 12VDC relay with the coil leads between the two points of the cutoff switch itself. When the cutoff switch is closed, the relay would see 0 volts across its coil and be de-energized; when the cutoff switch is open, the relay would see 12 volts across its coil and energize.
The second part of the circuit is that this relays contact is in series with the "Generator Turn ON Signal" between the PCM and the alternator. When the cutoff switch is open, the relay energizes and opens the "Generator Turn ON Signal" disabling the alternator output. If this works without any issues, I no longer see a need to run a seperate cable from the alternator to the cutoff switch. At this point, this is all theory, so I cannot confirm if the alternator will function in the manner I have indicated.
If the cutoff switch was used to disconnect the battery when the vehicle is in storage, you would simply need to also pull the relay to prevent any battery discharge.
In the current method (as per diagram) with having the cable running direct from the alternator to the battery it will provide slightly less voltage drop for charging than it would by backfeeding the alternator power through the main power lead going to the engine bay, but the difference in voltage at the battery should be negligible.
Currently I have a 1/0 running from my battery cutoff switch to my distribution point in my engine bay. From the distribution point, I have a 1/0 running to my starter and I am going to use a #4 to the alternator.
Would this method be suitable to meet the NHRA rules, or am I missing something? What size wire is used from the LS1 alternator in the stock configuration?
In relocating my battery to the rear, I am sorting out how I will cutoff the alternator power when the cutoff switch is in the Off position.
With the NHRA ruling identifying that the battery switch needs to cutoff all power, I am wondering if the alternator power to the battery can be cutoff in a different manner than the diagram I found on tech.
In thinking out of the box, instead of bringing a #2 cable from the alternator, back to the battery side of the cutoff switch, I am thinking of going a different route, but need some more knowledgeable input before I proceed.
As the LS1 alternator has a "Generator Turn ON Signal" (R15 output from the PCM) to enable the alternator output charging, can this input to the alternator also be used to disable the alternator output? If it can be used without damaging the alternator or PCM, here is my idea.
Install a 12VDC relay with the coil leads between the two points of the cutoff switch itself. When the cutoff switch is closed, the relay would see 0 volts across its coil and be de-energized; when the cutoff switch is open, the relay would see 12 volts across its coil and energize.
The second part of the circuit is that this relays contact is in series with the "Generator Turn ON Signal" between the PCM and the alternator. When the cutoff switch is open, the relay energizes and opens the "Generator Turn ON Signal" disabling the alternator output. If this works without any issues, I no longer see a need to run a seperate cable from the alternator to the cutoff switch. At this point, this is all theory, so I cannot confirm if the alternator will function in the manner I have indicated.
If the cutoff switch was used to disconnect the battery when the vehicle is in storage, you would simply need to also pull the relay to prevent any battery discharge.
In the current method (as per diagram) with having the cable running direct from the alternator to the battery it will provide slightly less voltage drop for charging than it would by backfeeding the alternator power through the main power lead going to the engine bay, but the difference in voltage at the battery should be negligible.
Currently I have a 1/0 running from my battery cutoff switch to my distribution point in my engine bay. From the distribution point, I have a 1/0 running to my starter and I am going to use a #4 to the alternator.
Would this method be suitable to meet the NHRA rules, or am I missing something? What size wire is used from the LS1 alternator in the stock configuration?
11-14-2011, 05:22 AM
#2
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Re: Battery Relocation - LS1 Alternator cutoff
That would work, but why not kill power to the PCM instead of a halfway cutoff for the alt
The rule is there to totally kill the car in the event of a problem and if the charging system is down, fine, but you left the fuel system out. If the PCM is shut down, charging and fuel goes down from not having 12v on a single 18ga wire
The rule is there to totally kill the car in the event of a problem and if the charging system is down, fine, but you left the fuel system out. If the PCM is shut down, charging and fuel goes down from not having 12v on a single 18ga wire
11-14-2011, 08:14 PM
#3
Re: Battery Relocation - LS1 Alternator cutoff
Thanks Pocket. With the cutoff switch disconnecting the battery, I was so focused on the alternator I missed the simple solution ... Killing the power to the PCM will be a lot easier to install as well as I can keep it all inside.
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