Electrical Questions

[FJNos]

Hey all. I'm getting ready to undertake a electrical project in my FJ and I had a few questions. I'm planning on wiring everything into an RTMR block similar to what I drew up in the attached diagram. Initially I was going to wire up my own RTMR, but it wasn't going to be cost effective so I ended up getting a prewired one from Shockworks that came with a nice mount for the engine bay (LINK).

Since I'm going to running wire to the back of the truck for my rear lights I figured I would add a couple of 12v plugs in the trunk. Thinking about it more would I be better off setting up a small fuse block in the rear instead? I can't imagine I would use more than 60 amps off of that, so what size gauge would I need? It would probably be a 20-25 foot run from the battery so 4awg or 2awg?

Regarding crimping the 4awg cable for the RTMR power and ground, I have a hammer style crimper that I was use in a bench vise. Would that be sufficient?

Anything else I should consider before starting?

 

[DaveInDenver]

Sizing wire can be slightly confusing since it's not usually yes or no. Most people rely on rule of thumb charts which are usually conservative.

The key things you're balancing are cost and space against margin of safety (mainly a question of insulation rating) and voltage drop. Remember for your calculation that the circuit is a loop, so going 20 feet from the battery to the load requires 40 feet of conductor. If you use the frame as a return this sometimes can be essentially a very large conductor if you take care to make sure the connection is clean and large enough on both ends.

What do you anticipate running from the rear block? Looks like you have things I'd be concerned with voltage stability, radios for example, on the main block. Fridges can be voltage sensitive where excessive voltage drop can trip under voltage protection as well as increase wear on the motor. Lights aren't voltage sensitive necessarily but high voltage drop will make them dimmer.

So if you assume by 20 feet you mean 40 feet total (out and back) with non-critical uses where some voltage drop is acceptable then 60 A on 6 AWG will have 7.4% voltage drop (about 1 V) with at least 90°C insulation should work (I'm assuming an ambient of 40°C) in typical use.

If you want something with more margin then 4 AWG will be around 4.7% drop (about 0.6 V) for a 40 foot loop at 60 amps. Temperature rise will be negligible in this case so even 75°C insulation should be fine.

 

[FJNos]

Thanks for the detailed answer Dave. Yes full circuit would be around 40 feet I think, though I believe there is a factory ground point in the rear where the bottle jack mount is. I'd have to look into that.

From the rear block I would like to run at least 2 12v sockets and/or possibly an SB50 Anderson plug if I ever end up getting a fridge.

Any recommendations on where buy good quality cable for a reasonable price, either online or in Denver?

 

[bassguyry]

I installed a fuse block for a few additional 12V circuits in my 100 a couple of weeks back. I bought pretty much everything from Amazon, except the Blue Sea 12V panels. I ran 6AWG cable from the battery to the fuse block in the rear of the truck, and then 10AWG from the fuse block to both panels. Here's what I bought:

6AWG cable
10AWG cable
Crimper
Fuse Block (they make larger ones, if you need more circuits)
Heat Shrink Connectors

The cable definitely wasn't cheap, but I also wasn't interested in buying in bulk, which I think is where you'll really see the savings. I bought a couple of Duralast battery lug connectors from AutoZone for the 6AWG cable. I think they were about $3/ea.

 

[DaveInDenver]

Electrical suppliers:
https://risingsun4x4club.org/xf/threads/source-for-electrical-connectors.11861/

E&G is local:
http://www.eandgterminal.com

Other options:
https://www.parts-express.com
https://www.wiringproducts.com
https://www.waytekwire.com
https://www.delcity.com
https://www.powerwerx.com

 

[DaveInDenver]

I don't care a lot for those hammer crimpers. I use a set of monster crimpers but being in Grand Junction it's not much help. Pretty sure someone else in the club closer to you has them, too.

An SB50 is serious and probably overkill for a fridge. The smallest terminal you can get for those is 10 AWG. Regular 15/30/45A PowerPoles are fine for a fridge, it's what I use anyway.

 

[FJNos]

Cool thanks for the input guys. Del City is having a sale on wire. I picked up 50ft of 6 gauge welding cable for just under $20. Now I just need to find someone with a nice crimper.

 

[bassguyry]

Cool thanks for the input guys. Del City is having a sale on wire. I picked up 50ft of 6 gauge welding cable for just under $20. Now I just need to find someone with a nice crimper.

The crimper I linked to above (on Amazon) worked just fine on 6 gauge cable, just FYI.

 

[DaveInDenver]

The crimper I linked to above (on Amazon) worked just fine on 6 gauge cable, just FYI.

It's only listed to 10 AWG and even at that it's only for quick-and-dirty single dimpling split seam terminals. They don't do a double crimp (on the insulation strain-relief) and certainly aren't very good for crimping battery terminals and lugs. If anyone would like I can write up the differences.

 

[bassguyry]

It's only listed to 10 AWG and even at that it's only for quick-and-dirty single dimpling split seam terminals. They don't do a double crimp (on the insulation strain-relief) and certainly aren't very good for crimping battery terminals and lugs. If anyone would like I can write up the differences.

I'm well aware they're only listed for 10AWG. My point was that they worked just fine for my installation - the lugs were super tight after crimping. Thanks for setting me straight, though.

 

[DaveInDenver]

I'm well aware they're only listed for 10AWG. My point was that they worked just fine for my installation - the lugs were super tight after crimping. Thanks for setting me straight, though.

Just offering my $0.02 having done aerospace harnesses and having collected and calibrated lots of my own crimpers over the years.

A good crimp is more than just mashing them flat and with these larger closed barrel battery lugs you want to crimp enough to cold work them into a homogeneous mass without shearing any of the individual strands by over crimping. Dimpling is normally not the way to do them for the best conductivity. That's all those hammer crimpers do, too, just with more force.

 

[bassguyry]

Totally get where you're coming from, and again, I appreciate you setting me straight. I'll likely never run 6AWG cable again, and wasn't super interested in buying a tool that I'd only use once. I figured I'd give it a shot with the cheap Amazon crimpers, and if it worked, great. If not, I'd buy something else.

It's kind of like using a 7/16" socket because I can't find my damn 10mm socket - is it ideal? Nope. Will it work? Maybe. Do I need to go buy a lifetime supply of 10mm sockets? Absolutely.

 

[DaveInDenver]

Totally get where you're coming from, and again, I appreciate you setting me straight. I'll likely never run 6AWG cable again, and wasn't super interested in buying a tool that I'd only use once. I figured I'd give it a shot with the cheap Amazon crimpers, and if it worked, great. If not, I'd buy something else.

I'm just coming from a position that the expertise and capability to make good wires and cables exists in the club so no reason not to ask. I have the Delphi/Sumitomo/Yazaki factory sealed and unsealed crimpers, battery lugs up to 4/0, Molex, PowerPole, Fastex, coax, uninsulated barrel. No need to even spend the $20 for a one-time tool even.

It's kind of like using a 7/16" socket because I can't find my damn 10mm socket - is it ideal? Nope. Will it work? Maybe. Do I need to go buy a lifetime supply of 10mm sockets? Absolutely.

 

[Yeti]

I'm trying to finish up a similar aux 12v power run and was hoping someone near Arvada with a hydraulic crimper could help me complete the crimping of 3 terminal lugs. Wire is 2 AWG. Cable and lugs are ready to crimp.

Thanks
Greg

 

[J1000]

I've got the Harbor Freight hydraulic crimper and it works pretty well. You can come use it anytime. PM me for address I'm near C470 and Quincy.

https://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html

 

[Yeti]

Awesome thank you. That's the one I was going to buy if I could find one to use. Sending PM now.