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Old 07-28-2009, 10:54 AM   #31
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wouldn't the resistance of the connector, prob deans, nullify the loss of using smaller gauge wire?
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Old 07-28-2009, 11:50 AM   #32
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wouldn't the resistance of the connector, prob deans, nullify the loss of using smaller gauge wire?
No, losses compound.
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Old 07-28-2009, 12:40 PM   #33
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No, losses compound.
so say the connector is losing .3v and the smaller wire .1v

that setup would have .4v less than bigger hardwired?
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Old 07-28-2009, 12:57 PM   #34
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so say the connector is losing .3v and the smaller wire .1v

that setup would have .4v less than bigger hardwired?
Yes... but its nowhere NEAR half a volt. You need to add a zero or two in there after the period.
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Old 07-28-2009, 03:43 PM   #35
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so do you guys think the TQ 13AWG has more strands of wire than stock 12AWG Sphere and Deans Wet Noodle 12AWG wires?

I'm coming close to getting a Hakko Soldering Station so I can be prepared to swap out motor wires, as soon as I decide on the wire.
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Old 07-29-2009, 12:04 AM   #36
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Here is an example using common wire sizes and how to figure out your expected voltage drop. Most of the time you will not be on the wood (full throttle).

If you are going to make short runs attach a heat sink to the bare wire to prevent the solder from flowing up the cable. The more flexible the cable the easier it is to fit in your car.

The TQ 13AWG and 10AWG products are as flexable as the wet noodle 12 AWG product. If you have de-soldered your motor wires or caused the jacket to get wet looking you should shorten the wire length further or switch to the 10 AWG.

1ft 14 awg copper wire = 0.00257 ohms
1ft 12 awg copper wire = 0.00162 ohms
1ft 10 awg copper wire = 0.00101 ohms

How Many Amps Does My Motor Draw:
4.5T Novak = 530 Watts @ 7.4V
P = IE
I = Watts / Volts
I = 71.62 Amps Draw

What is the Voltage Drop:
V = AMPS x OHMS

14 AWG = 0.1840V
12 AWG = 0.1160V
10 AWG = 0.0729V
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Last edited by Capt'N_Slow; 07-29-2009 at 12:29 AM.
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Old 07-29-2009, 09:18 AM   #37
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Another item that everyone seems to ignore is that internally to the ESC, all of the power to the motor is basically flowing through effectively a single PC board trace to the solder post. That PC board trace is nowhere near 13 gauge wire.

Probably the only difference you could (potentially) notice would be from a dead stop, where the motor is drawing the most current. At full throttle down the straight, the motor isn't drawing anywhere near the current that is does from a dead stop. From the examples listed above, if your motor maxed out at 130A current draw, it might only draw 15A going down the straight.

As an example, a 6 minute run for me in 17.5 TC at the Carpet Nats used about 2200mAh (or 2.2Ah). Since it was a 6 minute run (1/10 of an hour), the average discharge rate was approximately 22A (2.2Ah / 0.1h) = 22A

Use the easiest wire to work with. Most of the guys in 1/12 scale use 16ga wire, since it doesn't bind the rear pod up.
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Old 07-29-2009, 09:27 AM   #38
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Solid copper wire and multistrand wire do not have the same resistance or current capacity. What you do show though is the voltage drop is VERY low. Also that 4.5T will pull a lot more amps then that under hard acceleration. Those dyno numbers are not taken under much load. Although current loads higher then that are for very short periods of time but the high current spikes can cause heat build up in the wire if it is under spec. I highly doubt anyone could need more then TQ 13 gauge for any 7.4V application. If you were to try insane speed runs with 11V+ systems you might want to upgrade. Otherwise I challange anyone to notice a difference in feel or lap times on the track with anything more.
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Old 07-29-2009, 09:48 AM   #39
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Based on your comment, can we make the assumption that 40C (40A) batteries delivers well above average 22A. That's all you need? Anything above would be a waste since Motor + ESC can not draw that much power?!

Is my assumption flawed? Just trying to understand the physics behind this.

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Originally Posted by CarbonJoe View Post
Probably the only difference you could (potentially) notice would be from a dead stop, where the motor is drawing the most current. At full throttle down the straight, the motor isn't drawing anywhere near the current that is does from a dead stop. From the examples listed above, if your motor maxed out at 130A current draw, it might only draw 15A going down the straight.

As an example, a 6 minute run for me in 17.5 TC at the Carpet Nats used about 2200mAh (or 2.2Ah). Since it was a 6 minute run (1/10 of an hour), the average discharge rate was approximately 22A (2.2Ah / 0.1h) = 22A
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Old 07-29-2009, 10:55 AM   #40
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Originally Posted by javacrazy View Post
Based on your comment, can we make the assumption that 40C (40A) batteries delivers well above average 22A. That's all you need? Anything above would be a waste since Motor + ESC can not draw that much power?!

Is my assumption flawed? Just trying to understand the physics behind this.
In general, most LiPo packs are rated at their continuous current capability (like 40c), and their peak current is generally 2x their continuous current rating. So, a 40c 5000mAh is usually capable of 200A continuous, 400A peak.

The discussion of LiPo ratings, internal resistance, etc. is outside the scope of this thread, but suffice it to say that no RC motor is going to draw 200A continuous. It would melt in short order. Peak current for various motors I'm not sure about, other than the general statement that all motors are going to draw their peak current from a dead start. What has been discussed in various LiPo threads is that in general, the total capacity is more important than some arbitrary current rating, since the less of the capacity you use, the higher the average voltage is.
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Old 07-29-2009, 02:25 PM   #41
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Good points. I wonder if the technology of Li-po's are getting "better" for their own good? Since current ESC's and Motors are probably not capable of harnessing the type of Amp draw that (for example) a 5200 40C+ Li-po can supposedly discharge at, right now, thus not needing the smaller gauge motor/battery wires at the moment. I mean ESC's do get hot and so do motors today...I guess we will need to see 'hardier' components that would handle such Amp draw and still keep cool. Time will tell.

Hmm...interesting. Maybe TQ13 in BLACK it is?!
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Old 07-29-2009, 04:51 PM   #42
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Quote:
Originally Posted by Capt'N_Slow View Post
Here is an example using common wire sizes and how to figure out your expected voltage drop. Most of the time you will not be on the wood (full throttle).

If you are going to make short runs attach a heat sink to the bare wire to prevent the solder from flowing up the cable. The more flexible the cable the easier it is to fit in your car.

The TQ 13AWG and 10AWG products are as flexable as the wet noodle 12 AWG product. If you have de-soldered your motor wires or caused the jacket to get wet looking you should shorten the wire length further or switch to the 10 AWG.

1ft 14 awg copper wire = 0.00257 ohms
1ft 12 awg copper wire = 0.00162 ohms
1ft 10 awg copper wire = 0.00101 ohms

How Many Amps Does My Motor Draw:
4.5T Novak = 530 Watts @ 7.4V
P = IE
I = Watts / Volts
I = 71.62 Amps Draw

What is the Voltage Drop:
V = AMPS x OHMS

14 AWG = 0.1840V
12 AWG = 0.1160V
10 AWG = 0.0729V
While the math is correct, the derivation is wrong. The rated 540W is the power output of the 4.5T motor, and is not the power input. What you want is the power input to calculate the voltage drop on the wires. As an example, refer to this dyno information of a 13.5t Novak motor. The power input is well over 700W, but the power output is only around 70W @ 3200RPM. Novak 13.5T Sentry Dyno Data RAW. Notice that there are errors up to 3600 RPMs because the sensor was not able to record current past 106Amps. We have fitted a 200 amp sensor to the dyno, yet I have no data to show at the moment, however I suspect even a 13.5t motor producing a max of only 205W can draw around 130Amps before 3000rpms.

What this means is that the current draw is much higher than what you calculated therefore the voltage drop is higher. Please refer to my other post, the voltage drop can be as different as a 0.15V for 1' of wire when comparing 12AWG and 13AWG for a 13.5t motor.
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Old 07-29-2009, 04:55 PM   #43
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Quote:
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the voltage drop can be as different as a 0.15V for 1' of wire when comparing 12AWG and 13AWG for a 13.5t motor.
Thank goodness all my wires are only a few inches long
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Old 07-29-2009, 05:38 PM   #44
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mattnin, I fully agree with you in regards. Without a doubt using real world amp draw numbers for a 4.5T motor instead of using novak's specification would be more relavent.

I just wanted to answer the question in a simple but factual way. Speaking from experence using mod 4.5 to 6.5T motors I've had my connections desolder causing my esc to blow and have had the insulation get wet or melt off. 100+ amps draw is not unspeakable given the right conditions.

Most of the time you are either rolling into full throttle or out but hardly have any time at the wood.
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Old 07-29-2009, 05:47 PM   #45
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Originally Posted by seaball View Post
funny thought:
this miniscule (and imperceptable) voltage difference was the basis mfr's used to separate $40 packs from $80 packs when round cells were king. further, an even smaller difference in voltage has been a key element of the 'sponsored vs. privateer' equipment agrument for just as long.

now, we've moved on to software updates ...
the answer to the original question depends on what you want to prioritize. a larger wire is going to show a smaller voltage drop without question. but, if it were me, i'd err to the side of color every time. (r/c is hurting for style to begin with).

exactly.

V x A=Watts, watts is power.

Sure the difference in volts is small, rise in amps is cube to rise in volts or there abouts. The result may be 20watts extra or 5% more power with a 400W system. May seem insignificant but as we say on the flying field "ounces add up to pounds".
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