Battery Cut off switch .

[richard lane]

Hi I just want to check (as I have had a bit of conflicting advice) when fitting a cut off switch do I need a 110 amp or 240  neg. lead to go from battery to switch ?

Just want to make sure before I do this sometime this week.

Many thanks Rich

[Jonathan Kay]

Which circuit diagram are you using?

Jonathan

[richard lane]

I havent seen a circuit diagrams , was going off a friends car who sent me a pic of his that he had done .  

His just disconnected the neg lead putting the cut off between that lead and then attaching new lead going back to battery neg terminal.  

Looked easy to do !?  

Rich

[philwaters]

The normal way is to cut into the positive side, with a high wattage resistor then connected to ground on one of the smaller terminals. This way, you cut the circuit and also dump the output from the alternator to ground to prevent any running on.

If you just want to isolate the battery, then I guess either way would work, but if you want to have it as an emergency cut-off to switch off the engine from outside of the car, then I think you need the alternator connection/resistor.

There is a diagram on this thread https://www.lotus7.club/forum/techtalk/battery-cut-switch-0

[richard lane]

Thank you Phil

Just want it to isolate battery really.

Cheers Rich

[philwaters]

In that case, cutting into the negative is probably the easiest way. If you cut into the live but don't have the resistor I think you could damage the alternator if you try to isolate while it's running (but don't quote me on that... )

[Tony Whitley]

Every day's a school day, I'd never heard of 110A or 240A leads. I suppose it makes some sense given that it assumes 12V.

Resistor:

The resistor is to dump the current produced by the alternator in between you cutting the supply to the battery and the alternator stopping spinning. The reason behind this is so you don't risk blowing the rectifier diodes in the alternator.

[anthonym]

https://www.lotus7.club/forum/techtalk/master-cutoff-switch-cut-positive-or-negative-or-both

you might find the above interesting.

my current (!!) conclusion is that cutting the negative using a giant relay is best, but I didn’t do it because changing the entire engine loom wasn’t feeling like a wise time to make such a change. 

Cut out circuits here: https://www.lotus7.club/forum/techtalk/cut-out-circuit-yes-where

and I used to assume all circuits are fused, but they are not https://www.lotus7.club/forum/techtalk/fused-or-unfused-and-after

anthony

[patibbitts]

Q: Where is the FIA type removable 'red flag handle' cutout switch normally mounted- for Road / track day use?

 

 

Q: How is it mounted? - (there appears to have been one mounted on my car previously, on the passengers side of the scuttle, in the triangle shaped windscreen support bracket. Only issue is there appeared to only be one central hole in the aluminium scuttle side - given that there appears to be two mounting screw holes to hold the isolator in place , how come I only have one hole through the side of the scuttle?

Q; is there a switch available, with one central fixing nut instead of the two smaller fixing holes - or am i missing something?

 

Answers appreciated ,

Regs,

[Jonathan Kay]

There are notes and a template in the Assembly Guide. What model and year is your Seven?

Could you add a photo of what you've currently got?

Jonathan