Culminator Posted April 13, 2016 Share Posted April 13, 2016 Just fitting a battery master switch to my VX HPC and got some cable from Merlin Motorsport. What I've received though is 16mmsq and rated at 110amps. It also has 30mm written on the cable. Is this man enough? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted April 13, 2016 Member Share Posted April 13, 2016 In your set-up will this carry: The big current to the starter (not the low current from the switch to the solenoid)? The current from the alternator? Everything else in the car?There's a Club Guide to fitting a master switch, but I think there are variations that aren't covered in it.Jonathan Link to comment Share on other sites More sharing options...
Culminator Posted April 13, 2016 Author Share Posted April 13, 2016 I know how to fit it Jk, just want to know if the cable is man enough. It's the same as any 7 BMS set up. Cheers though. Link to comment Share on other sites More sharing options...
OliverSedlacek Posted April 13, 2016 Share Posted April 13, 2016 Current ratings for a 16 square mm CSA cable vary according to the standard used, and 110A is a typical continuous rating. This is comfortably more than anything except the starter current.The starter current is not continuous, so other considerations apply. This cable has a resistance of 0.001 ohms per meter, so the voltage drop along one meter of cable would be 0.1 volts when the starter draws 100 Amps, 0.2 volts at 200 Amps etc. How much of a drop you can live with is debatable, but aiming at 0.5V drop and 200 Amp starter current would limit you to no more than 2.5 meters of cable length. Link to comment Share on other sites More sharing options...
Culminator Posted April 13, 2016 Author Share Posted April 13, 2016 Thanks Oliver. Battery to switch is 1.7m max and switch to starter is a maximum of 1.5m, so a combined length of 3.2m. Is that too much then or could I buy some thicker cable for the battery to switch route and use the 16mm cable just for the switch to starter? Link to comment Share on other sites More sharing options...
jackb_ms Posted April 14, 2016 Share Posted April 14, 2016 I am looking to update this part of the wiring of car also and I have been looking at "welding cable" which is design for high current application and is flexible.the one I am looking at is 35mmsq which is rated at 220A which should be enough for the starter motor.It seems also to be more cost effective... Jack Link to comment Share on other sites More sharing options...
Culminator Posted April 14, 2016 Author Share Posted April 14, 2016 I've sent my 15mmsq back and will investigate further. Spoke to Redline today and they have 20mmsq cable (170amp I think) which Caterham supply, so that must be OK. Link to comment Share on other sites More sharing options...
OliverSedlacek Posted April 14, 2016 Share Posted April 14, 2016 I think for the length you need and a big-ish engine, going up to the 20 or 25 square mm cable is worthwhile. Link to comment Share on other sites More sharing options...
Culminator Posted April 15, 2016 Author Share Posted April 15, 2016 Picked my new cables up from Redline this afternoon. Got a pair of 20mmsq cables complete with ends and also got a very quick refund from Merlin, no quibble. Happy days, thanks both! Link to comment Share on other sites More sharing options...
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