Dual Battery Setups! Let's see them! Multiple Batteries Thread!

Yeah, this is the part that scares me - poking through the skirt.

 

I did this since I knew I was going to be running multiple feeds. Currently I only have the Switch-Pros feeding thru but dual battery switch and front camera is coming up.
https://www.tacomaworld.com/threads/wires-through-the-firewall-the-right-way.531829/

 

Yup. The chart on this page has the same info, just a bit less cluttered:
http://www.offroaders.com/technical/12-volt-wiring-tech-gauge-to-amps/

@Mugshot89 switches are a gimmie. Fuses might not be. Just make sure you fuse everything thats hot. aka from the battery to the bus bar, and then the lead running to each thing. Also, using the frame as ground could lead to problems in the future when the connection(s) start to corrode. If its in your budget, probably just as well to run a dedicated neg. line back to the bus bar.

 

What guage wire did you run from your Aux battery to the Body ground point on the fender? It looks like you still have the factory Starting battery to Body ground link 8 or 4ga.. NOT GOOD. That link be large enough to match the run to the Aux battery plus any other grounds you have attatched to it..

 

Pretty easy on the OR... there's a plug on the firewall that the brake booster partially covers on other trims that will work with a new grommet and loom. I ran all my cables through there and while the MT trucks have to deal with the clutch pedal bracket on the inside (really just make sure you don't scrape insulation off the wires), for an AT truck it's super easy to just pull them through the insulation and run them up into the dash.

 

It works as long you never get a ground fault elsewhere. Not doing a chassis ground at the load, (or as close as possible) you set up the potential to destroy equipment with stray current. There are only a few narrow cases where it's a less bad idea.

 

What do you mean stray current?

 

maybe he meant a short?

 

Hi, thanks for this insight - I'm just using the wire that came with the kit - "USA made, high strand count, 2 AWG welding cable is used in our kits." Can you expand a bit on your point? Basically, the body ground needs to be higher gauge than everything else?

 

That little wire from the fender to the Starting battery is a bottle neck, it needs to accomodate everything upstream from it.

 

what's the formula for calculating this?

 

Use a wire gauge chart (several were linked on the previous page of this thread) and find the maximum amperage you could theoretically see in the system.

 

Cheers - TW continues to be an amazing educational resource!

 

Find the amps or watts rating of your accessories attached to the aux battery(convert them all to amps), add them up(maybe add some margin), use a chart linked from the others to determine cable size for the length from the aux battery to the starting battery. The little link from the starting battery to the firewall needs to be that size wire. Just think of connecting a garden hose to the business end of a firehose connected to a fire hydrant . You ain't putting out no fires with it, except with wiring it could start a fire.

 

@Sandman614 I think you're confusing power wire requirements with grounds. Power wires are gauged for consistantly carrying amps and not losing voltage over long runs. Ground wires only momentarily carry amps until circuit protection kicks in...voltage drop not important.

 

Electricity doesn't read wire diagrams. It will always find the path of least resistance. Stray current is when current finds different paths then intended. An example: I was wiring my boat, and inadvertently disconnected a critical ground. Each time I turned on the running lights, the horn would let out a low groan. There was less resistance for the current to ground it's way through the horn.

The classic "worst case scenario" is if the primary ground wire attaching your battery to chassis were to fail. You decide to run a ground wire back to the battery for some lights, or a two way radio, or something. If the primary battery ground fails, engine crank current has the potential to go through your installed equipments ground wire, which takes it through the equipment. If the ground is fused, then you'll probably pop the fuse. If not, you'll likely destroy that equipment, and melt that wire. Hopefully you don't start a fire.

 

Electricity flows in a circle the ground wires should be sized the same as positive wires.

 

That assumes the piece of equipment has a "chassis ground" though, like a household AC appliance would. Do DC devices have that? Specifically things like LED bars, air compressors, fridges, etc? I dont think they do, but Im not sure. Maybe radios do, but again, Im not sure

 

is there a possibility you can fab me the exact same one you have, i am trying to bolt on a air tank in the aux batt location thanks

 

Sort of, yes. With DC, it's different reasoning. It's not a safety ground like an AC appliance. Most (not all) DC device chassis are DC grounded. Its quite often I've seen a two way radio work just fine with the ground wire disconnected. Which is not terrible, but can add some problems. With a two way radio install, you definitely want/need the chassis ground wire to be a lower impedance path to ground then the coax shield. The coax shield almost always is grounded at the antenna install point to setup an RF ground plane. The coax shield is also grounded to the radio chassis. It's less then ideal to have the coax braid carrying DC ground current. Running a sufficiently long enough wire back to the battery, could possibly raise it's resistance enough that the radio grounds through the coax braid instead. With every install I do, I make sure to power the radio with the coax disconnected, and the radio not yet bolted to it's bracket. To make sure I have found a working chassis ground for my ground wire.

A coworker wired up a fire truck wrong one time. All the strobe lights and the back up "beep, beep, beep" alarm were finding a ground path through the two way radio, and through the coax. The coax was carrying more current then it could and started to melt. Almost started a fire on a fire truck, lol.