Mk2 Chopper Posted July 4, 2020 Report Share Posted July 4, 2020 Update: I've now fitted the switch as follows. Quote Link to post Share on other sites
Mk2 Chopper Posted July 4, 2020 Report Share Posted July 4, 2020 Can't upload these photos other than one post at a time even though I've reduced the size, if there was one thing I wish we could have is more memory for pictures! Quote Link to post Share on other sites
Mk2 Chopper Posted July 4, 2020 Report Share Posted July 4, 2020 Next one: Quote Link to post Share on other sites
Mk2 Chopper Posted July 4, 2020 Report Share Posted July 4, 2020 Inside the car: Quote Link to post Share on other sites
Mk2 Chopper Posted July 4, 2020 Report Share Posted July 4, 2020 A picture of the new earth cables: Quote Link to post Share on other sites
Peter Cobbold Posted July 4, 2020 Report Share Posted July 4, 2020 Never switch the engine off with the switch, it will blow the alternator diodes. Quote Link to post Share on other sites
BRENDA1 Posted July 4, 2020 Report Share Posted July 4, 2020 I used the top of an aerosol rattle can to cover the terminals just cut the lid around the cables and it pushes on to the base. Mike Redrose Group Quote Link to post Share on other sites
Mk2 Chopper Posted July 4, 2020 Report Share Posted July 4, 2020 47 minutes ago, Peter Cobbold said: Never switch the engine off with the switch, it will blow the alternator diodes. Thanks, I did know, but it's a good reminder to anyone who reads this. 44 minutes ago, BRENDA1 said: I used the top of an aerosol rattle can to cover the terminals just cut the lid around the cables and it pushes on to the base. Mike Redrose Group I did have one that fitted, but when I started trimming it it broke, as I've fitted this to the earth side it's at less risk to drop a spanner onto it, but it would look nicer covered. Gareth Quote Link to post Share on other sites
ntc Posted July 4, 2020 Report Share Posted July 4, 2020 In motorsport I think the switch must be fitted on the positive side. Quote Link to post Share on other sites
john.r.davies Posted July 4, 2020 Report Share Posted July 4, 2020 Absolutely, ntc! A cut-out on the earth cable leaves everything connected to the other side of the battery live, so that in an incident any conductor could complete the circuit, negating the cut-out's function. But the OP, "Mk2 Chopper"(?) wanted to prevent his battery going flat, from small feeds to things like radios. I hope this does what he wants, as I fear there is some larger drain. If he has an alternator, Peter Cobbold is quite right, not if he has a dynamo. There is a version of the FIA cut-out for alternator cars (surprise!) that incorporates two secondary switches, to supply the engine etc. when the switch is on, and shunt the current from the 'dying' alternator to earth, through a massive resistance when it's turned off. Like this - switch 1 is ON whne the main switch is OFF. Switch 2 is ON when the main switch is ON. Quote Link to post Share on other sites
stuart Posted July 4, 2020 Report Share Posted July 4, 2020 44 minutes ago, ntc said: In motorsport I think the switch must be fitted on the positive side. At least the supply side for those of you still running positive earth Stuart. Quote Link to post Share on other sites
ntc Posted July 4, 2020 Report Share Posted July 4, 2020 Glad you agree as for those silly battery terminal units dangerous just wait while you forget it one day and turn the key you had better make sure the body grommets are in good order. Quote Link to post Share on other sites
Peter Cobbold Posted July 4, 2020 Report Share Posted July 4, 2020 (edited) A switch in the earthy is as safe as switching the live. Once the battery earth terminal is no longer connected to the body you can touch anything 'live' to earth and nowt will happen. When disconnecting the battery terminals with a spanner you always do the earthy first. Work on the live first and the spanner may short several hundred of amps to anything earthed- body, battery clamp, cable whatever. Neil is right: for racers, live terminal switched, earth lead wrapped in yellow tape. Peter Edited July 4, 2020 by Peter Cobbold Quote Link to post Share on other sites
Hamish Posted July 4, 2020 Report Share Posted July 4, 2020 1 hour ago, ntc said: In motorsport I think the switch must be fitted on the positive side. Why does the battery earth have to be Yellow in motorsport. I presumed it identified which one to be cut in the event of an incident ?? Quote Link to post Share on other sites
Mk2 Chopper Posted July 4, 2020 Report Share Posted July 4, 2020 58 minutes ago, Peter Cobbold said: A switch in the earthy is as safe as switching the live. Once the battery earth terminal is no longer connected to the body you can touch anything 'live' to earth and nowt will happen. When disconnecting the battery terminals with a spanner you always do the earthy first. Work on the live first and the spanner may short several hundred of amps to anything earthed- body, battery clamp, cable whatever... Exactly my reasoning. Gareth. Quote Link to post Share on other sites
SeanF Posted July 4, 2020 Report Share Posted July 4, 2020 5 hours ago, Mk2 Chopper said: Inside the car: Hi Gareth, That looks great. I'll be following your lead. Are you able to provide links to the cables/switch you bought? Only difference is my battery poles at the forward side of the battery, not the rearward. Many thanks again, Sean Quote Link to post Share on other sites
john.r.davies Posted July 4, 2020 Report Share Posted July 4, 2020 (edited) Well, up to a point Lord Cobbold! A cut-out on the earth side will leave all of the supply side live, at a higher potential than earth. Any defect, anything that will allow that to go to earth, will. If, say, that was on the earth side of a fuel pump, then the pump will continue to run, or else fuses will blow and wires overheat and burn. A supply side cut-out is safe - an earth side is not safe. No scrutineer would allow it. But the OP wanted to stop small drains on his battery - if it'll do that, fine. Yes, Hamish, the yellow taped earth cable was an early attampt to do the same. It's still in the race regs, but no longer necessary, becasue of the cut-out. BUT!!! I've seen an engine fire, on a rally car. The marshals pulled the cut-out toggle - and the electric fan went on running, fanning an engine fire and blowing away the extinguishant the marshals squirted in under the bonnet. They had to cut the earth lead to stop the fan! The fan was wired in some odd way, so maybe the yellow earth lead is a last resort! Edited July 4, 2020 by john.r.davies Quote Link to post Share on other sites
ChrisR-4A Posted July 4, 2020 Report Share Posted July 4, 2020 Nothing wrong with using the earth side for a basic cut off, however I used the positive side so I could run a separate wire from the switched side of the cutout to a CB radio and a cigarette lighter socket with an inline fuse. This allows items to be powered when ignition is off but cutout is still on, then when leaving car with the cutout key everything is off. Chris Quote Link to post Share on other sites
Mk2 Chopper Posted July 4, 2020 Report Share Posted July 4, 2020 1 hour ago, SeanF said: Hi Gareth, That looks great. I'll be following your lead. Are you able to provide links to the cables/switch you bought? Only difference is my battery poles at the forward side of the battery, not the rearward. Many thanks again, Sean Hi Sean, Just adjust the length of the cable depending how your terminals are. All items from ebay, the switch: https://www.ebay.co.uk/itm/121587624274 The earth cable (I went for the thickest 35mm2 with 10mm crimp): https://www.ebay.co.uk/itm/262593761906 The other earth wire at the same 35mm2 (10mm crimp one side and 8mm the other) https://www.ebay.co.uk/itm/262763772172 And the bolts are stainless M5 with M5 nylock nuts from: https://www.ebay.co.uk/itm/271919529340 And https://www.ebay.co.uk/itm/282653431674 Hope that helps Gareth Quote Link to post Share on other sites
DaveN Posted July 4, 2020 Report Share Posted July 4, 2020 On 6/18/2020 at 7:04 PM, AarhusTr6 said: Years ago my batterywent flat at Heathrow, the AA recovery guy who came to bump start me was adamant that cars parked near airports lost their charge quicker than all others, ie that he was always coming out to the airport for flat batteries and often to new cars . . still wondering if he thought it true or it was a wind up!! Your AA man was right... newer cars having immobilisers and car alarms. Every time Concorde took off for about a minute afterwards all one could hear was car alarms! Quote Link to post Share on other sites
SeanF Posted July 5, 2020 Report Share Posted July 5, 2020 12 hours ago, Mk2 Chopper said: Hi Sean, Just adjust the length of the cable depending how your terminals are. All items from ebay, the switch: https://www.ebay.co.uk/itm/121587624274 The earth cable (I went for the thickest 35mm2 with 10mm crimp): https://www.ebay.co.uk/itm/262593761906 The other earth wire at the same 35mm2 (10mm crimp one side and 8mm the other) https://www.ebay.co.uk/itm/262763772172 And the bolts are stainless M5 with M5 nylock nuts from: https://www.ebay.co.uk/itm/271919529340 And https://www.ebay.co.uk/itm/282653431674 Hope that helps Gareth That's brilliant Gareth. Many thanks, Sean Quote Link to post Share on other sites
Peter Cobbold Posted July 5, 2020 Report Share Posted July 5, 2020 (edited) 15 hours ago, john.r.davies said: Well, up to a point Lord Cobbold! A cut-out on the earth side will leave all of the supply side live, at a higher potential than earth. Any defect, anything that will allow that to go to earth, will. If, say, that was on the earth side of a fuel pump, then the pump will continue to run, or else fuses will blow and wires overheat and burn. A supply side cut-out is safe - an earth side is not safe. No scrutineer would allow it. But the OP wanted to stop small drains on his battery - if it'll do that, fine. Yes, Hamish, the yellow taped earth cable was an early attampt to do the same. It's still in the race regs, but no longer necessary, becasue of the cut-out. BUT!!! I've seen an engine fire, on a rally car. The marshals pulled the cut-out toggle - and the electric fan went on running, fanning an engine fire and blowing away the extinguishant the marshals squirted in under the bonnet. They had to cut the earth lead to stop the fan! The fan was wired in some odd way, so maybe the yellow earth lead is a last resort! John, I do not see a circuit once the battery has had its connection to the body (earth) disconnected. So it is as safe as a switch on the live side. Without a circuit through the battery no current can flow. Perhaps RobH will adjudicate ? Peter Edited July 5, 2020 by Peter Cobbold Quote Link to post Share on other sites
RobH Posted July 5, 2020 Report Share Posted July 5, 2020 Electrically it really doesn't matter which side the circuit is broken Peter, provided we are dealing with a battery which only has two exposed terminals. The old style of battery where the cells are connected with exposed lead strips are another set of hazards altogether. I can only assume the FIA requirement of yellow tape is to ensure that no-one uses metal cutters on the live connection, as an inadvertent earth while doing so would be interesting to say the least - even more so if spilled petrol was present. As a guess their reason for mandating switching in the live side only, may be that with the earth switched, some distortion of the body in an impact might just contact the earth terminal of the battery directly and so render the switch useless. It is difficult to imagine how bodywork damage could similarly negate the action of a switch in the live side. I do agree that the case you quote for disconnecting the earth first/reconnecting it last makes eminent sense, when metal tools are being used on or near the battery terminals and permanently-live connections like the solenoid. That is why I have the disconnector in the earth lead on my car. Quote Link to post Share on other sites
Mike C Posted July 5, 2020 Report Share Posted July 5, 2020 Just now, RobH said: Electrically it really doesn't matter which side the circuit is broken Peter, provided we are dealing with a battery which only has two exposed terminals. The old style of battery where the cells are connected with exposed lead strips are another set of hazards altogether. I can only assume the FIA requirement of yellow tape is to ensure that no-one uses metal cutters on the live connection, as an inadvertent earth while doing so would be interesting to say the least - even more so if spilled petrol was present. As a guess their reason for mandating switching in the live side only, may be that with the earth switched, some distortion of the body in an impact might just contact the earth terminal of the battery directly and so render the switch useless. It is difficult to imagine how bodywork damage could similarly negate the action of a switch in the live side. I do agree that the case you quote for disconnecting the earth first/reconnecting it last makes eminent sense, when metal tools are being used on or near the battery terminals and permanently-live connections like the solenoid. That is why I have the disconnector in the earth lead on my car. +1. Quote Link to post Share on other sites
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