muddy4x4xfar Posted February 28, 2014 Share Posted February 28, 2014 high guys im hoping to wire in my aux fusebox onto my defender this weekend. i have a fuse box which is capable of 100amp per bank. there are 2 banks. my question is if i was to run a 170amp cable from my battery to my relay then to the 170amp mega fuse then from there carry the cable on . then join 2 100amp cables to the 170amp cable (so spliting the 170amp cable off into 2) then joining the lower amp cables to the 2 clamps on the fuse box. would this work ok? im trying to save having to buy 2 relays and extra fuses and have them run through 1 . also saving space. many thanks for your time guys Quote Link to comment Share on other sites More sharing options...
Maverik Posted February 28, 2014 Share Posted February 28, 2014 Might be worth drawing it out on some paper for clarity... Quote Link to comment Share on other sites More sharing options...
muddy4x4xfar Posted February 28, 2014 Author Share Posted February 28, 2014 hope this helps. obviously if anyone has any better ideas they'd be much appreciated. im wiring it so it will come on with the ignition hence the relay. my only problem is whether the cable can be split off to the 2 positive clamps on the aux fuse box. Quote Link to comment Share on other sites More sharing options...
vulcan bomber Posted February 28, 2014 Share Posted February 28, 2014 Why not have 1 side ignition controlled and the other not...Depending on where your putting the fuse box I wouldnt bother fusing it just 2 lengths of 16mm cable inside some conduit would do. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted February 28, 2014 Share Posted February 28, 2014 Depends how much current, in total, you'll ever draw through it. Are you likely to draw more than 100A from all your accessories ever? Quote Link to comment Share on other sites More sharing options...
muddy4x4xfar Posted February 28, 2014 Author Share Posted February 28, 2014 Depends how much current, in total, you'll ever draw through it. Are you likely to draw more than 100A from all your accessories ever? well the fuse box im fitting will take 100amp per side and theres 2 sides. ill be running 4 heated seats 4 spot lights 2 fog lamps 3 work lights cb radio , handsfree kit, airlocker kit etc. theres quite a lot going on it. Quote Link to comment Share on other sites More sharing options...
landy andy. Posted February 28, 2014 Share Posted February 28, 2014 I would run the 170 cable to one fuse board terminal then put a bridge link in, just joining the two terminals. Andy Quote Link to comment Share on other sites More sharing options...
redneck Posted February 28, 2014 Share Posted February 28, 2014 First off, using cable by it's amp rating is not the best way to do it. You need to base it on an accepable voltage loss, or how many volts do you want your item to see, 3% loss is really the most you want in any system. We all know what happens when an inadequate size cable is used e.g headlamps!!! Here is a useful quick tool for working out minimum cable sizes http://www.solar-wind.co.uk/cable-sizing-DC-cables.html The fuse is to protect the cable, you have a potential to run 170 amps through a 100amp cable if you do as you plan. p.s. why would have 170 amp fuse on 200 amp circuit Quote Link to comment Share on other sites More sharing options...
miketomcat Posted February 28, 2014 Share Posted February 28, 2014 Based on the above calculator you need 50mm2 cable for a 2m run @ 170amps what the hell are you planning to run off this fuse box! I know people that run a winch on smaller cable for a longer run (not that I like or agree with there system but you get my point). Mike Quote Link to comment Share on other sites More sharing options...
muddy4x4xfar Posted February 28, 2014 Author Share Posted February 28, 2014 Based on the above calculator you need 50mm2 cable for a 2m run @ 170amps what the hell are you planning to run off this fuse box! I know people that run a winch on smaller cable for a longer run (not that I like or agree with there system but you get my point). Mike i get what your saying. admittedly im only learning the electronics side of things. but im one of those boys that tries to get the best out of what i do . so ideally im looking for my best options. an as youll see i dont go for the easy stuff haha but i do like the idea of what your saying, and i also like the bridging idea from landy andy. Quote Link to comment Share on other sites More sharing options...
redneck Posted February 28, 2014 Share Posted February 28, 2014 Based on the above calculator you need 50mm2 cable for a 2m run @ 170amps what the hell are you planning to run off this fuse box! I know people that run a winch on smaller cable for a longer run (not that I like or agree with there system but you get my point). Mike The calculator works on an out and back cable run, i.e 2m run equals 4metres of cable. Quote Link to comment Share on other sites More sharing options...
redneck Posted February 28, 2014 Share Posted February 28, 2014 i get what your saying. admittedly im only learning the electronics side of things. but im one of those boys that tries to get the best out of what i do . so ideally im looking for my best options. an as youll see i dont go for the easy stuff haha but i do like the idea of what your saying, and i also like the bridging idea from landy andy. Make sure the bridge is the same size cable as the main feed. Not the 100amp cable Quote Link to comment Share on other sites More sharing options...
Litch Posted February 28, 2014 Share Posted February 28, 2014 I think you are confusing the rating of the fusebox with what you will be drawing from it. The chances are you won't have everything turned on at the same time (what is the output of your alternator, 65A or 100A?) plus you have to consider the standard items (lights, heater etc). In the electrical industry it is called dIscrimination (AKA common sense). 55W spots = 4.6A each. 90W heated seat elements = 7.5A. CB & handsfree = negligable. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted February 28, 2014 Share Posted February 28, 2014 I think the bridge is a bad idea, the terminal on the fuse box will only be rated at 100A, and therefore melt if you draw the full 170A through it. I would suggest that two fuses, two 100A relays with 100A cable would be the best solution and hardly any more expensive (the fuse) and the relays should be cheaper being lower rated. VWP do a good range of higher current relays, up to 200A I think. Quote Link to comment Share on other sites More sharing options...
muddy4x4xfar Posted March 1, 2014 Author Share Posted March 1, 2014 I think you are confusing the rating of the fusebox with what you will be drawing from it. The chances are you won't have everything turned on at the same time (what is the output of your alternator, 65A or 100A?) plus you have to consider the standard items (lights, heater etc). In the electrical industry it is called dIscrimination (AKA common sense). 55W spots = 4.6A each. 90W heated seat elements = 7.5A. CB & handsfree = negligable. Its a 120amp on a defender td5 Chances are as it has no roof the heated seats will always be on that been the main thing. An the alpine sound system. Quote Link to comment Share on other sites More sharing options...
ejparrott Posted March 1, 2014 Share Posted March 1, 2014 I've just fitted two busbar fuses boxes in The 109. They are fed with 50A cable each, one direct from battery so permanently live, the other controlled by my 100a ignition controlled relay, which includes the headlights so I can't leave them on when I leave the car. There's actually very little on the permanent box. Quote Link to comment Share on other sites More sharing options...
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