...which is the point of using a relay.

Thanks, the chassis ground question was what I was thinking of. I hadn't thought about not having enough capacity to handle the amperage; does anyone know if there's a big ground wire (e.g. battery or alternator to chassis ground) or just a small one? I'll poke my head under the hood to look tomorrow, but I'm not sure I'll be able to tell at a glance.

 

I understand how a relay works. I have installed a few. I don't see how it is the solution to the OPs first post, if he is trying not to connect the high amp wire directly to his battery.

 

If it isn't powered when the truck is shut off it won't affect the BMS.

 

Ok, that makes sense.

 

I looked at a random WARN winch and it looks like it’s rated at 400A at max pull. I highly doubt the voltage monitor will handle that. You may be able to hook something up that will disconnect the voltage monitor when the winch is in use. That should (might?) force the alternator into a default output mode that will help keep the voltage up while operating the winch.

 

Basically this is true and when truck is running, tapping directly off Battery Negative for limited usage will not have an overwhelming change to the BMS measured SOC. it re-calculates every 6 hours of sleep period.

I would be more concerned with features like a stereo, continuous lighting or a second battery being always hooked up.

Note, there are two different types of BMS sensors. For non-S/S vehicles, Ford uses a Hall Sensor (doughnut around the cable). Ideally is to route wiring thru this but a winch cable wouldn't fit or connect to chassis ground. The second style used for S/S vehicles is a sensor mounted directly on battery negative post. it really provides a secondary post which you can attach wiring since the sensor is part of the battery terminal.

Edit for following: I just checked the rating for the BMS sensor attached to the battery and can handle up to 1500A

 

Have you considered adding the Snow Plow Pkg, to disable unnecessary electrical loads during winch operation?

 

What accessory wire are you guys talking about? Nobody should be tapping into any wires for winch power. Direct connection to battery for that... relays for turning it on/off if your winch supports it. Same goes for high power light bars... never wire power THROUGH a switch use a relay. But use a relay that can handle the power... winches draw a LOT of power. I don't remember what size fuse but I'd recon at minimum a 50amper is in there and most relays you find are MAYBE 20amps. I use 40amp fuses myself but still, my winch is hard wired to my battery... it's always got power. Then to activate it you use your wiring harness/switch/controller/etc.. almost every winch has one of these for trucks.

Also never power a winch when the truck is off... that's a LOT of power you are drawing from the battery, even with the Fords system, you shouldn't do that on any truck. Always start the truck.

 

They are talking about running a hot wire from the battery to a relay, to the winch, to the chassis.

They are talking about using a switch to energize the relay.

They are talking about powering that switch from a wire that is only hot when the truck's ignition is either ON or on ACC. That way, if the truck is turned off, you can not accidentally leave the winch powered, draining the battery.

 

...again I suggest looking into adding the snow plow pkg to use a switched circuit to activate the winch - same as with a snow plow. It's very easy to do.


https://www.f150forum.com/f118/2015-...trofit-381030/