SQOD Squad - Stupid Question Of the Day (27 Viewers)

[linuxgod]

This is kind of a hypothetical but I’m working on a project where the answer will help me a bit. So I would appreciate any input to help me learn.

If a run two wires back from my battery to my cargo area (one for positive and one for negative) and connect these to a DC-DC converter to increase the voltage to 24V.
30 amps will be going into the converter and 15 will be going out as the voltage is doubled.

When I’m considering the gauge of the wire from and to the battery, I know the blue sea systems wire chart is meant to consider the full length of the circuit (out and back), but could I make the negative wire going back to the battery smaller gauge since in will be only half of the amperage at that point?

And yes, I fear this question highlights a complete misunderstanding of the way electricity works….

Voltage doesn't matter for wire size, amps do. 14 gauge will do 15 amps, 12 gauge is for 20 amps, and 10 gauge is for 30 amps. After that I have to look it up but I think 8ga = 40A. Keep in mind you shouldn't plan to sustain >80% load, so to run a continuous 30A load you need an 8ga wire, but a short peak is fine on a 10ga wire so long as the continuous load is <=24A.

Now if you're DC-DC converting to 24V, then your 24V loop (+ from the converter to the device(s), - going back to the converter) could be 14ga, but the 12V run to and from the converter should be 10ga minimum (and probably 8ga if you're going to sustain 30A).

BTW on the 12V side if your DC-DC converter is in the trunk you can ground to the body (i.e. a 3rd row seat bolt) and that effectively increases your return wire gauge since that ground is going to be way thicker than any wire you run.

 

[lx200inAR]

This is kind of a hypothetical but I’m working on a project where the answer will help me a bit. So I would appreciate any input to help me learn.

If a run two wires back from my battery to my cargo area (one for positive and one for negative) and connect these to a DC-DC converter to increase the voltage to 24V.
30 amps will be going into the converter and 15 will be going out as the voltage is doubled.

When I’m considering the gauge of the wire from and to the battery, I know the blue sea systems wire chart is meant to consider the full length of the circuit (out and back), but could I make the negative wire going back to the battery smaller gauge since in will be only half of the amperage at that point?

And yes, I fear this question highlights a complete misunderstanding of the way electricity works….

@linuxgod Definitely already has this covered but should add, once you put the DC to DC converter in, everything on the 24v side of that converter has to be treated as a new circuit. So your 24v runs will only exist downstream of the DC to DC converter. It will still be 12v up to the DC to DC converter for + and - wires and the wire will have to be sized appropriately (whether that is using the frame as a return or using the same gauge wire as your + wire).

 

[MCtree]

Voltage doesn't matter for wire size, amps do. 14 gauge will do 15 amps, 12 gauge is for 20 amps, and 10 gauge is for 30 amps. After that I have to look it up but I think 8ga = 40A. Keep in mind you shouldn't plan to sustain >80% load, so to run a continuous 30A load you need an 8ga wire, but a short peak is fine on a 10ga wire so long as the continuous load is <=24A.

Now if you're DC-DC converting to 24V, then your 24V loop (+ from the converter to the device(s), - going back to the converter) could be 14ga, but the 12V run to and from the converter should be 10ga minimum (and probably 8ga if you're going to sustain 30A).

BTW on the 12V side if your DC-DC converter is in the trunk you can ground to the body (i.e. a 3rd row seat bolt) and that effectively increases your return wire gauge since that ground is going to be way thicker than any wire you run.

Ah. Okay. Thanks.
I guess I need to look at them as two separate loops. The 12V circuit between the converter and the battery and then the 24V circuit between the converter and the load device.
It just seems odd if it’s all 360 watts than the negative wouldn’t all be at the lower amperage since it’s all on the negative side of the load.

And yeah, I know that the vehicle body can be used as the return of the circuit.
But that then makes me wonder why anybody would ever run a return line?

 

[TeCKis300]

This is kind of a hypothetical but I’m working on a project where the answer will help me a bit. So I would appreciate any input to help me learn.

If a run two wires back from my battery to my cargo area (one for positive and one for negative) and connect these to a DC-DC converter to increase the voltage to 24V.
30 amps will be going into the converter and 15 will be going out as the voltage is doubled.

When I’m considering the gauge of the wire from and to the battery, I know the blue sea systems wire chart is meant to consider the full length of the circuit (out and back), but could I make the negative wire going back to the battery smaller gauge since in will be only half of the amperage at that point?

And yes, I fear this question highlights a complete misunderstanding of the way electricity works….

All good questions. In regards to the ground wire, best practice is not to run an independent ground back to the battery. You really do want to use chassis as the ground. What that means is use a short section of wire, to ground to a chassis bolt nearest to the DC-DC converter. Make sure to abrade the paint to ensure a solid electrical connection.

Reason why you don't want to run a ground is that there is a risk in failure modes with the main chassis ground, that this new ground wire becomes the ground path for many accessories. Something it was never sized for, then creating a fire risk.

 

[MCtree]

@linuxgod Definitely already has this covered but should add, once you put the DC to DC converter in, everything on the 24v side of that converter has to be treated as a new circuit. So your 24v runs will only exist downstream of the DC to DC converter. It will still be 12v up to the DC to DC converter for + and - wires and the wire will have to be sized appropriately (whether that is using the frame as a return or using the same gauge wire as your + wire).

Thank you, that helps.

The reason I am pondering this is kind of along the lines of what you say. So if the circuit to the converter is 25feet (out and back) and then the circuit after the converter is another 10’, when I’m using the blue sea wire gauge chart, should I consider each length separately since they will have different amperage’s? Or do I need to somehow consider the total 35ft length?

Edit: in seeing your response, @TeCKis300 , perhaps this question is moot.

 

[cruisin4bruisins]

Great thread idea...

I've searched mud and google, and forgot to check before I left this morning....does anyone know the height of the heritage with the rack installed. Picture of my parking garage @ work behind. 8'2" clearance....

View attachment 3586893

Was this picture taken in Boston per chance? Specifically in seaport?

 

[Nothinghead]

So if the circuit to the converter is 25feet (out and back) and then the circuit after the converter is another 10’, when I’m using the blue sea wire gauge chart, should I consider each length separately since they will have different amperage’s? Or do I need to somehow consider the total 35ft length?

As he says below, you have two completely separate circuits: one is the 12v side and the other on the 24v side so choose your wiring based on each individual circuit.

@linuxgod Definitely already has this covered but should add, once you put the DC to DC converter in, everything on the 24v side of that converter has to be treated as a new circuit. So your 24v runs will only exist downstream of the DC to DC converter. It will still be 12v up to the DC to DC converter for + and - wires and the wire will have to be sized appropriately (whether that is using the frame as a return or using the same gauge wire as your + wire).

 

[MCtree]

As usual, I do appreciate everybody’s input here. It is helpful.

I mean, I am sure I will still find a way to burn my LC to the ground, but I appreciate the education.

 

[das100]

Was this picture taken in Boston per chance? Specifically in seaport?

Few hours south in Arlington, VA..couple miles outside of DC. Never been to Boston, would like to take it in one day.

 

[cruisin4bruisins]

Few hours south in Arlington, VA..couple miles outside of DC. Never been to Boston, would like to take it in one day.

That's so funny this looks exactly like outside my office in Boston, I've also seen a black 200 series with bronze rims park on the street, looks identical to your rig, I'll take a pic if i see it again lol I'm actually moving from Boston to Raleigh, NC in a couple months and my parents live in Arlington, I recommend not coming here in the winter, beautiful in the summer though

 

[das100]

That's so funny this looks exactly like outside my office in Boston, I've also seen a black 200 series with bronze rims park on the street, looks identical to your rig, I'll take a pic if i see it again lol I'm actually moving from Boston to Raleigh, NC in a couple months and my parents live in Arlington, I recommend not coming here in the winter, beautiful in the summer though

That is too funny. This is right outside my office in Clarendon and I just got back from Raleigh picking it up on Monday. I think you’ll like it…seemed like a fun mix of busy and quiet.

 

[HighRanch]

.

 

[AnyMal]

Voltage doesn't matter for wire size, amps do. 14 gauge will do 15 amps, 12 gauge is for 20 amps, and 10 gauge is for 30 amps. After that I have to look it up but I think 8ga = 40A. Keep in mind you shouldn't plan to sustain >80% load, so to run a continuous 30A load you need an 8ga wire, but a short peak is fine on a 10ga wire so long as the continuous load is <=24A.

Now if you're DC-DC converting to 24V, then your 24V loop (+ from the converter to the device(s), - going back to the converter) could be 14ga, but the 12V run to and from the converter should be 10ga minimum (and probably 8ga if you're going to sustain 30A).

BTW on the 12V side if your DC-DC converter is in the trunk you can ground to the body (i.e. a 3rd row seat bolt) and that effectively increases your return wire gauge since that ground is going to be way thicker than any wire you run.

Also remember most circuits are designed with a 20% overcapacity.

 

[AZLX570]

2013 LX

I forgot to reset the trip meter after I changed my oil/reset maintenance reminder. Is there any way to see how many miles are left in the 5K interval?

Am deciding on whether to change it early based on an upcoming road trip.

 

[gaijin]

2013 LX

I forgot to reset the trip meter after I changed my oil/reset maintenance reminder. Is there any way to see how many miles are left in the 5K interval?

Am deciding on whether to change it early based on an upcoming road trip.

Go ahead and change your oil and filter - start over.

 

[AZLX570]

Got it. An early 1k or at most 2k miles won't hurt anything - cheap.

Speaking of the maintenance reminder, is it ~500 miles that the message starts popping up?

 

[linuxgod]

2013 LX

I forgot to reset the trip meter after I changed my oil/reset maintenance reminder. Is there any way to see how many miles are left in the 5K interval?

Am deciding on whether to change it early based on an upcoming road trip.

Not sure your road trip distance but I’ve sent oil samples to blackstone at ~6500 miles where I had done 2000 miles of pure city stop-and-go, 3500 miles of towing at 70-75 in 4th gear, about 100-150 miles of 4Lo trails, and then a bit of urban/suburban driving and they said there was plenty of TBN left and to repeat with 8000 miles and send them another sample. So if you might go 6000-6500 miles on your oil for one cycle I really wouldn’t worry… I wouldn’t routinely go 10k miles between oil changes like the book says but you probably could do it and still put 250-300k on your engine

 

[m12345y]

A little discouraging that the wrenches I like so much don’t seem to be available anymore..

I’d just look for a 20-200 inch-lbf wrench. Then eventually get a 15-85 or 100ft-lbf. To be really effective with a 200 you probably also need a 75-250 for some of the front suspension stuff.

It sucks but doing all this work requires the proper tools. I think between my cars and bikes I’m up to five torque wrenches at this point..

Thanks for the tips and encouragement; I did it, replaced all four globes and AHC fluid. Two front ones need drill and hammer, two rear ones quick and easy.

But I fear I have air in my lines:
1) When I bleed the fronts (both 2nd and 3rd/last time), the initial burst appears to be thick and darker pink, but quickly become clear and light pink as seen from the vinyl tube. But then looking at the tub, it seems to be more like air bubbles than anything else (sediments)
2) When pressuring up, I hear a quick and clearly audible, not necessarily loud, (air) discharge sound. It's like those buses release air pressure brakes.

PS. the fluid tank and initial bleed was terrible brown.

Any advice?

 

[bloc]

Ok, I know the mirror select switch needs to be on either side to trigger the side-view mirror adjustment in Reverse.

But.. how do I store a new reverse mirror position? I've adjusted them, then tried every combination I can think of setting 1/2/3 program spots while in park, in reverse, in neutral, drive.. I've tried clearing the key - assigned seating position memory, everything. Yet the mirrors keep going to the same incorrect spot on reverse.

And yes I've read the owner's manual.. I can't see anything specific about this.

Thoughts?

 

[linuxgod]

Ok, I know the mirror select switch needs to be on either side to trigger the side-view mirror adjustment in Reverse.

But.. how do I store a new reverse mirror position? I've adjusted them, then tried every combination I can think of setting 1/2/3 program spots while in park, in reverse, in neutral, drive.. I've tried clearing the key - assigned seating position memory, everything. Yet the mirrors keep going to the same incorrect spot on reverse.

And yes I've read the owner's manual.. I can't see anything specific about this.

Thoughts?

To set the mirror setting: Press Set then 1, 2, or 3. That’s it.

I don’t think there’s a way to change the mirror position when you go into reverse, but if it’s set to L or R they will point downwards when you reverse, if it’s in the center they don’t move