Battery and Alternator Disconnect Switch Question - LotusTalk - The Lotus Cars Community
 
LinkBack Thread Tools Display Modes
post #1 of 10 (permalink) Old 08-24-2014, 11:46 AM Thread Starter
Registered User
 
Join Date: May 2008
Location: Grand Rapids, MI
Posts: 606
Battery and Alternator Disconnect Switch Question

I would like to install a disconnect switch for safety on the track and convenience during maintenance.

In searching for switches, I have found two types; switches for cars with alternators and switches for cars without alternators.

With Eliges, are there any harmful consequences to a system like this:

Alternator---battery---switch---starter & rest of the vehicle electrical system
Everything but the switch would have its own ground.

I am proposing this system because it seems to be the most simple. Am I missing some untoward effect of simply opening the circuit at that point?

Thanks,

Jason

06' Fed Elise

My frame, rear subframe, steering rack, A-arms, front crash structure, suspension uprights, and fuel tank are stock.
jasondew is offline  
Sponsored Links
Advertisement
 
post #2 of 10 (permalink) Old 08-24-2014, 12:28 PM
He's on fire!
 
jds62f's Avatar
 
Join Date: Jun 2006
Posts: 3,050
Haven't heard of this myself. Maybe I'm missing something but I would just install a beefy switch (http://www.reallylightstuff.com/elec...ff-switch-kit/) between the battery post and the rest of the electrical. The only thing storing energy is the battery (and maybe ecu, but it won't discharge to the rest of the car)

"Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life."
jds62f is offline  
post #3 of 10 (permalink) Old 08-24-2014, 02:40 PM Thread Starter
Registered User
 
Join Date: May 2008
Location: Grand Rapids, MI
Posts: 606
The alternator needs to be switched off also to stop spark and fuel pump if the engine is running.

Jason

06' Fed Elise

My frame, rear subframe, steering rack, A-arms, front crash structure, suspension uprights, and fuel tank are stock.
jasondew is offline  
 
post #4 of 10 (permalink) Old 08-24-2014, 04:25 PM
He's on fire!
 
jds62f's Avatar
 
Join Date: Jun 2006
Posts: 3,050
Quote:
Originally Posted by jasondew View Post
The alternator needs to be switched off also to stop spark and fuel pump if the engine is running.
If you cut the battery out of the system, the car (and by virtue the alternator) will never see any power.

With no spark or fuel, I can tell you the engine won't be running. Are you wanting to turn the car on, then cut power to the alternator and have everything run off the battery? Maybe you should explain a little more what it is you're trying to accomplish...

"Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life."
jds62f is offline  
post #5 of 10 (permalink) Old 08-24-2014, 04:35 PM
Registered User
 
holmz's Avatar
 
Join Date: Sep 2006
Location: Antipodes
Posts: 2,309
There are approved systems tat are sold.
Would one of them work?
holmz is offline  
post #6 of 10 (permalink) Old 08-25-2014, 05:41 PM Thread Starter
Registered User
 
Join Date: May 2008
Location: Grand Rapids, MI
Posts: 606
A battery disconnect switch does not disconnect the alternator. The alternator can still power the ignition and fuel pumps if the ignition is switched on. The purpose of a master disconnect switch is to provide a single switch to disconnect the battery and alternator. The RLS switch is just a battery disconnect.

I was confused: I was treating my 4 wire alternator as a 1 wire alternator. Different circuit designs apply to each.

It appears that a two pole switch that disconnects the battery and the alternator's field exciter wire is what is needed. This safe guards the alternator if the switch is opened while the engine is running and the ignition is on.

Does this sound correct?

I'm thinking of using one like this:link

Will the field exciter wire be cold with the ignition off and +13v with the ignition on? Will the other wires in the alternator harness behave differently? I can't tell from looking at it which small wire in the alternator harness is the field exciter wire.

Jason

06' Fed Elise

My frame, rear subframe, steering rack, A-arms, front crash structure, suspension uprights, and fuel tank are stock.

Last edited by jasondew; 08-25-2014 at 06:08 PM.
jasondew is offline  
post #7 of 10 (permalink) Old 08-25-2014, 06:36 PM
Registered User
 
mikelr's Avatar
 
Join Date: Mar 2006
Location: Newburgh, New York
Posts: 1,504
This is what I run,

Battery Isolator



and yes you are right, in that you have to isolate the alternator as well as the battery. You can actually isolate the excite wire or the charge wire to the battery.

00' S1 Exige
17' Jaguar F-Type R
94' S4 Esprit (SOLD)
14' Evora S (SOLD)
mikelr is offline  
post #8 of 10 (permalink) Old 08-28-2014, 12:35 PM
He's on fire!
 
jds62f's Avatar
 
Join Date: Jun 2006
Posts: 3,050
ah i understand now... for some reason it didnt come across to me in your first postings. Doesn't look like there is a ton of info out there... maybe check scca or lemons rules? they might be able to provide some guidance on safe setup? Other ideas would be to contact one of the sponsors that run race cars, they might be able to help too.

"Give a man a match, and he'll be warm for a minute, but set him on fire, and he'll be warm for the rest of his life."
jds62f is offline  
post #9 of 10 (permalink) Old 11-15-2014, 02:56 AM
Registered User
 
Join Date: Dec 2003
Location: Houston
Posts: 1,766
This switch cuts off both circuits and protects the alternator:

https://www.pegasusautoracing.com/pr...asp?RecID=1464
James A is offline  
post #10 of 10 (permalink) Old 11-15-2014, 09:32 AM Thread Starter
Registered User
 
Join Date: May 2008
Location: Grand Rapids, MI
Posts: 606
I ended up using this: Longacre. Works perfectly. Very stout construction.

Jason

06' Fed Elise

My frame, rear subframe, steering rack, A-arms, front crash structure, suspension uprights, and fuel tank are stock.
jasondew is offline  
Sponsored Links
Advertisement
 
Reply

  LotusTalk - The Lotus Cars Community > Motorsports > Safety

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the LotusTalk - The Lotus Cars Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
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:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



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
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome