View Full Version : Connecting heavy gauge wire to a relay
jonney_boy 05-31-2005, 07:38 AM I purchased a 12v relay the other day that is rated 40 amps. The relay has a bunch of quick connect tabs on the bottom.
The problem I have is finding connectors (female) that will fit the wires i want to use. I'm planning to run 8 guage wire and it seems that the biggest female quick connectors I can find are 10 guage.
For all the other people out there running relays (for things like switching inverters on and off) how did you connect them to your "heavier" guage wire.
As a side note, if I wanted to have a even bigger draw (and me being unable to find any relay bigger than 40 amps) is it possible to run 2 relays in parallel? is there any saftey concerns doing so?
There are bigger relays. Try http://www.grainger.com/ for the big stuff. As to a parallel, the problem would be if one relay failed to switch, and all of your current was going through the one relay.
PS: How is this a warranty question?
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offset 05-31-2005, 01:54 PM It may be easier to buy a relay harness and mate the wires.
http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=330-075
(There is also a harness with a diode jammed in if needed as well)
offset
ride5000 05-31-2005, 03:42 PM hope you have a big alternator and battery...
jonney_boy 05-31-2005, 09:32 PM haha.. oops.... I *though* I posted in the electrical fourm......... sorry...
As for big alternator and battery, I agree.... but that's part of another problem (that can be solved easily enough).
The relay will be powering either a large inverter (in the subaru for those times I need to run something beefy in a crunch like a corded drill... 7amps @ 120v) or in my pickup truck where i'm trying to install a removable, bed mounted winch (small winch draws 90 amps under full load, 40-50 amps under the kind of loads I expect to put on it).
As a final question, is there a good wire guage table on the net? I have done a search on it and some of the requirement seems kinda "funny". Some websites report that a 4 guage can handle a 50 amp load for only a max distance of 6 ft while other tables shows that an 8 guage can handle a 50 amp load for 20 ft........... (i'm looking to handle 50 amp load in 15-18 ft for short periods... like 2-3 mins at a time).
Psydotek 05-31-2005, 09:49 PM AWG wire table, courtesy of Ride5000
http://ken-gilbert.com/techstuff/AWG_WIRE_TABLE.html
:D
offset 06-01-2005, 01:58 AM Great calculators can be found on www.BCAE1.com for that info.
offset
Cougar4 06-01-2005, 03:08 AM You may need some 6ga. wire for much current. I don't know why you want a relay in the circuit but you may want to consider using an on/off switch for these things.
jonney_boy 06-01-2005, 03:12 AM I wanted a relay wired in the circiut for a few reasons.
1) For the inverter setup (in the subaru) I want to be able to kill power to the inverter completely, elimating any "drain" from the battery when not using the inverter
2) For the small winch in the pickup, I don't want a "hot" wire under the car when I don't need to use it, I'll prob only end up using the winch 2-3 months a year.
A switch would be really nice and simplify things a lot, but I have been unable to find a switch able to handle anything more than 20 amps, hence the 40 amp relay.
ducktapeguy 06-01-2005, 03:48 AM I picked up some 70/80 amp relays on the web somewhere (I think ebay), looks similar to the standard 40 amp relays but slightly larger. Also takes larger spade plugs, almost like an H4 spade.
As far as using the relay in your situation, not sure how it will hold up to motors in a winch or drill. Never heard of anyone connecting a winch through a relay, not that it can't be done. I would think a blade switch would be a better alternative to a relay. I just saw one today, they're usually in the automotive section as a battery kill switch, and I think rated to over 100 amps.
John UK 06-01-2005, 07:14 AM As a side note, if I wanted to have a even bigger draw (and me being unable to find any relay bigger than 40 amps) is it possible to run 2 relays in parallel? is there any saftey concerns doing so?[/QUOTE]
Don't connect relays in parallel. They will always break at slightly different times and the last one breaks the whole current.
Have you considered a battery isolator for the winch? The same might also be used for the inverter. They certainly take large cables OK and are rated well above your needs.
Large capacity relays are available. Try searching for split charge relays. These are used to supply a second battery and are rated to carry the alternator output.
Here is a 180 amp relay http://shopping.hotbot.co.uk/9433en5766163407.html
John
Cougar4 06-01-2005, 10:31 AM Doing a search for battery disconnect switches turned up a number of places. Here is a link to one that may help you.
http://www.centechwire.com/catalog/accessories/bds1.shtml
Psydotek 06-01-2005, 10:32 AM www.rallylights.com carries battery disconnect switches too.
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