Auxiliary battery wiring

[THEOZMAN]

for the BCDC charger you don't really need more than 8. and if you have 4 awg laying around, I would definitely use that. using 4 awg will give you the ability to do a jumpstart switch. so if your main battery died you can link the 2 directly, bypassing the BCDC and you can start the car off of the secondary.

 

[r2m]

Don't skimp on wire gauge. Use a wire gauge calculator like one of these:

http://www.paigewire.com/pumpWireCalc.aspx?AspxAutoDetectCookieSupport=1

Voltage Drop Calculator | Southwire

www.southwire.com

Online Wire Size Calculators & Tables

This wire size calculator will calculate the appropriate wire gauge for a circuit based on amps, voltage, distance, and load. This website provides a wire size calculator, voltage drop calculator, wire ampacity charts and more.

wiresizecalculator.net

The last one may be your the best calculator since you can input the distance/length of your wire.

 

[giovanni]

Don't skimp on wire gauge. Use a wire gauge calculator like one of these:

Couldn't agree more - particularly for long duration power use. I can *sort of* understand why Lexus used a smaller wire for the power seat motor - because it is a very short duration use case. When planning for long duration battery charge or inverter use case, you should err on the side of larger wire.

 

[THEOZMAN]

Couldn't agree more - particularly for long duration power use. I can *sort of* understand why Lexus used a smaller wire for the power seat motor - because it is a very short duration use case. When planning for long duration battery charge or inverter use case, you should err on the side of larger wire.

Accurate statement. That's why I am recommending using about 20 Amps with my connectors based on the factory wire size.

 

[arod2051]

Don't skimp on wire gauge. Use a wire gauge calculator like one of these:

http://www.paigewire.com/pumpWireCalc.aspx?AspxAutoDetectCookieSupport=1

Voltage Drop Calculator | Southwire

www.southwire.com

Online Wire Size Calculators & Tables

This wire size calculator will calculate the appropriate wire gauge for a circuit based on amps, voltage, distance, and load. This website provides a wire size calculator, voltage drop calculator, wire ampacity charts and more.

wiresizecalculator.net

The last one may be your the best calculator since you can input the distance/length of your wire.

Thanks for the links. I went to all of them. They are for AC voltage, so they ask for single-phase or multi-phase. I followed your guidance and looked for DC calculators. I don't know if this is good or not, but this is the link I found at the top of google:

Wire Size & Voltage Drop Calculator | GRE Alpha

This calculator will give you simple and quick estimates of wire length, expected voltage drop, and wire gauge. Type in your data and get your preferred wire size.

grealpha.com

I used the assumptions:

- 3% V-drop tolerance (1225D accepts down to 9V, so this is well above spec)
- 16 ft (I measured 15 feet with overages for bends, angles, etc -> then added a foot)
- 30A (At LiFePo4 profile of 14.5V the output current is 25.9A)

The calculator gives me 6awg.

 

[giovanni]

Here's the best / simplest wire size chart I've seen for DC. Note that it says to use the "round trip" distance - but this is designed for a boat where the ground is another wire, not a big chassis like we have on these vehicles.

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

 

[arod2051]

Here's the best / simplest wire size chart I've seen for DC. Note that it says to use the "round trip" distance - but this is designed for a boat where the ground is another wire, not a big chassis like we have on these vehicles.

Part 1: Choosing the Correct Wire Size for a DC Circuit - Blue Sea Systems

Engineering high quality marine electrical components for safety, reliability and performance

www.bluesea.com

I am also providing a current return path via same gauge back to starter batt.

This calculator and redarc datasheet says 8AWG is good to go.

That said, if I can fit 6awg, I'll fit that in.

 

[arod2051]

To close out this thread, we determined there is no good alternative 12v wiring that exists in the in the rear cargo area of a 2014+ base or premium model. The Luxury model can use the 12v wiring for the 3rd row seats.

I ended up dragging 6awg wire from the starter batt through the existing firewall grommet and along the sills, after unclipping the plastic. Hopefully, the pics explain better.

I am going to setup a distribution board that, hopefully, can sit inside the cavity between the rear side plastic and the wheel well quarter panel. I am going to put it split conduit in the engine bay but leave it open in the sill channel.