Thank you... yes, it helps answer. The motor is connected to a controller board, and apparently, the controller board is somewhat sensitive to voltage drop and it's run off a 12V battery, so as the motor is running, the 12.62 volts continues to drop over hours, so it's important. The improvement over today (with only 1 run of wire) would be reducing the voltage drop to 37.7 millivolts vs today at 75.36 (basically, a 50% improvement). I would assume it would run cooler as well, and less resistance, if the amperage were to run at 18A on occassion.

Voltage drop is not the problem -- it is battery capacity. The voltage drop is irrelevant when it comes to battery capacity. That is measured in Ampere-Hours. A battery only has so many of those, and when they're gone the battery voltage will drop like a brick in the rain.

 

I must have missed the fact that this is a Battery Powered Project .......

Not only will the Output Voltage gradually drop as the Battery becomes more Dis-Charged,
but the Battery also has an inherent "Internal-Resistance" which causes a
drop in Voltage with increasing Current Demands.

We still don't know anything about the project, or what the problem is .
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Voltage drop is not the problem -- it is battery capacity. The voltage drop is irrelevant when it comes to battery capacity. That is measured in Ampere-Hours. A battery only has so many of those, and when they're gone the battery voltage will drop like a brick in the rain.

Thanks.. is that just a regular rain or what if it's a major rain storm? Voltage drop due to the line is likely part of the problem. I understand the battery contains so much voltage, and as as I use the battery, the voltage will drop. The length of the wire run, the amps being pulled, bad connections, and the possibility of the wires heating up all impact voltage drop (if I understand the basics correctly).

I appreciate everyone's feedback and knowledge. I am going to give it a shot of using the 4 wires to deliver 12V battery (12.6 v) to the motor and see if it corrects the issue I am experiencing. The main item I was looking for is if I run 4 equal lengths tied together, does it give me lower voltage drop to my electric motor and controller and how does that compare to running just 6 AWG or 4 AWG vs my current run of 8 AWG. I will report back if my problem is fixed.

Thanks again everyone!

 

I must have missed the fact that this is a Battery Powered Project .......

Not only will the Output Voltage gradually drop as the Battery becomes more Dis-Charged,
but the Battery also has an inherent "Internal-Resistance" which causes a
drop in Voltage with increasing Current Demands.

We still don't know anything about the project, or what the problem is .
.
.
.

Sorry about that.. I assumed 12v would provide that information, but I assumed wrong. It's to power a trolling motor, and there's a remote that is used to control on/off/direction of the motor, and I have been told that voltage drop (since I am currently using 8AWG wire 20' to the motor) is the potential problem.

 

@L.Q.C. My meter does not unplug, and so that is not an option. To get around the aluminum wire problem with the connection above the meter I cut the feeders on my side of their crimp on splice, so that I am connecting copper to copper. And since I do the work standing on an 8 foot dry wooden ladder, and I am quite familiar with what to do, shocks are not a problem for me. BUT nobody else should try this!!
When I had to replace the cable down to the meter there was no other option, likewise when I had to connect another cable just down stream from the meter for the outside AC compressor feed. If an individual has an adequate understanding there should be no problems.
And the utility folks have never had an issue with the tag being cut. I did tell them that they are totally welcome to inspect their portion of the wiring at any time of any day if they so choose.

For trolling motor speed control the variations due to a changing supply voltage should not be any problem, and the complexity of additional wiring in a boat will probably outweigh any benefits of using doubled wires.
Given the importance of safety in a boat, versus the voltage drop in a fuse, the safe thing is to have a wire cutter near the battery connection to do a quick cut if a short circuit develops. At 12 volts there is no shock hazard but the power from a battery can cause a fire if there is a short circuit.

 

Sorry about that.. I assumed 12v would provide that information, but I assumed wrong. It's to power a trolling motor, and there's a remote that is used to control on/off/direction of the motor, and I have been told that voltage drop (since I am currently using 8AWG wire 20' to the motor) is the potential problem.

I'm sorry but I think what you have been told is misinformed. I urge you to try the experiment, and if the results make you happy, then so much the better.
Batteries apparently lose voltage because the internal resistance goes up (way more than the resistance difference between AWG #6 and AWG #8) as a result of the progress of a chemical reaction. Charging a rechargeable battery reverses that process. If voltage played ANY part in assessing battery capacity then it would show up in the measurement. But is doesn't the unit of measurement is Amperes times Hours, or Ampere-Hours.

For example a 12V battery could have more or less capacity than a 6V battery. You just can't which battery has more or less of anything from knowing just the voltage.

 

Trolling Motor,
Excellent, now we have a place to start.

Modern Trolling Motors are generally quite efficient,
your's might not be.

Your present Wiring Gauge has ZERO to do with ANYTHING in this situation,
the Wire terminations "MAY" have a very small effect if they look sketchy.

You still have not stated what problem you are trying to solve.

If you are simply trying to maximize Battery-Run-Time,
there may be several things you can investigate, or do.

The FIRST thing to consider is the condition of your Propeller,
it must be in Pristine, Factory-New-Condition,
with no nicks, cuts, roughness, or any imperfections of any kind.

Oh, and did I mention, PERFECT PROPELLER.

This deserves mentioning again ....... PERFECT PROPELLER.

The SECOND thing to consider is your method of Speed-Control ............

Many Trolling Motors have a VERY crude method of Speed-Control,
they simply have a large Power-Transistor,
(mounted inside the Motor housing for Water-Cooling),
and this Power-Transistor may be wired in series with the Motor at all times,
that would mean that you have a permanent ~0.7V to ~1.2V Voltage-Drop across the
Transistor under all conditions.
This Transistor is controlled by varying the Current supplied to it's "Base" Pin,
through a series of resistors in the Control-Housing.
This can easily add up to 30% or more, in wasted power.
If this is the type of set-up that you have, almost nothing else matters until
this situation is remedied by designing your own "Switch-Mode" Speed Controller.

The first thing to do is to determine exactly how your Trolling-Motor is Wired, IN DETAIL.

Create a Schematic Diagram, including the Values and/or Part-Numbers of all components.

There is a remote chance, (very remote), that if you call the Manufacturer,
they may send to you, or show you where to find,
a Wiring-Schematic and Parts list for your Trolling Motor.
It's worth a try.

If there are more than 2-Wires going down the tube to the Motor,
you will have to disassemble the Motor to determine exactly what is inside the housing.
If you find a Power-Transistor inside the Motor-Housing,
you will need to determine what type of Transistor "Package" it is in,
so that it can be replaced with a more appropriate, and far more efficient, MOSFET Transistor.
One Picture is worth a Thousand Words.

The FET can be easily controlled by a relatively simple
Pulse-Width-Modulated (PWM) Control Circuit,
which can have a simple, continuously variable, Potentiometer Control knob,
(a "Volume" Control),
or can be controlled with a Multi-Position-Switch for varying the Speed.

If you want to get really crazy, you can even control it via Blue-Tooth with your Phone.

There is basically nothing else you can do to improve performance
with the exception of buying a Better, and/or, Larger Battery.
You can also connect 2 Batteries in parallel,
IF, and ONLY IF,
the Batteries are identical in every way, including age.
If they are not identical, one Battery will run-down the other Battery.

You can also mount the Battery very close to the Motor,
and then run only low-Voltage Control wires to the "Control Station", what ever that might be.

DO NOT use your Engine Starter Battery to Power the Trolling Motor.
Use only a separate "Deep-Cycle" Battery.
If you want to buy a really top-notch Deep-Cycle-Battery, I recommend "Optima" Brand,
they are very expensive, and worth every penny.
They can be mounted up-side-down, or in any position.

When You get this stuff figured-out, post your Schematic here,
and one of the guys, or I, will show you how to convert to PWM using
an efficient FET Transistor, and a very small Control-Circuit-Board.
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Hmmm... I never did think that millivolts in the wires would amount to even a hill o' beans.

 

It may be that the present PWM driver circuit is more affected by the voltage than any other part of the system. I think that the TS has mentioned that a few times.

 

First, I want to thank everyone for their time responding to my posts, which weren't always clear. I do appreciate the help. I still have the dilemma (I got side tracked for awhile).

The issue is that I believe that voltage drop is impacting a controller that runs the trolling motor (speed, turning, GPS lock). The manufacturer has indicated that the voltage to the unit (that controls the board that takes commands from a remote) needs to be about 12V or more or you can have connectivity issues with the remote that is used to interact with the trolling motor (speeds, turning, GPS lock, etc.).

I put my boat back together, in normal configuration and took it out for a test drive, and here are the numbers that came back on voltage, as measured at the TM, at different speeds. The battery is <3 months old and tested good by throwing a 100amp test on it for 8 seconds, no dead cells, etc.

While starting at 12.67V, as I increase the speed on the motor, the amp draw increases, as does the voltage drop (as expected). Is this excessive (see chart) , and back to my original question, I have 2 positive and 2 negative 8AWG wires running about 18ft, but only using 1 set. using both sets together (same length) terminating together (2 positive, 2 negative) and running 1 wire the last foot of so (TM only has 2 wire inputs) would likely reduce the voltage drop by about 50%?
Thanks again!

 

Thanks for posting some data. Now we can see that the voltage drops 1.5 volts at 19 amps.This tells me that thereis a problem some place because with 2 number 8wires it should be much less.
The quick and easy test is to feel along the current path and find whatever gets hot. Somehow,18 watts are being turned into heat, which ought to make something a bit warmer.

So now for some more searching. The first place to check is at the battery terminals, and see if the battery voltage drops at all. Then, with a more sensitive meter, read the drop between the battery posts and the clamp that connects. THis should be a very small voltage. Then check between the clamp and the wire.

 

MisterBill2,

Are you telling me that that the voltage drop is too much for 1 positive and 1 negative wire running about 18ft is too much, that there's an issue along the path somewhere (or connections). Here's a diagram of the connections from the battery to the TM plug, note that only 2 wires (top 2 in diagram) are being used at this time to deliver electricity to the trolling motor.

 

YES, basicly, it seems like more of a voltage drop than there should be with that size of wire. But where are you measuring that voltage that dropped?
AND, just feeling the connection points should provide a clear hint as to where the voltage drop is. I doubt that it is in the wires themselves. Of course, it may also be that the battery voltage is dropping a bit.

 

You are measuring the "gross" voltage drop of the entire system,
but what you keep referring to is "The Wire Gauge" ............
If you want to determine the Voltage-Drop due to Wire-Resistance
then measure the actual Voltage-Drop of the Wire,
that is, connect your meter to each end of ONE of the Wires running to the Motor,
then double that Voltage number.

There is absolutely no way that you are loosing almost 10% of your Voltage,
in a huge Copper-Wire, with only ~20-Amps flowing through it.
It just can't happen that way.

You are measuring the "Voltage-Sag" of the Battery,
plus every other intermediate connection between the Battery and your testing points,
and then thinking that it's ONLY that fat Copper-Wire that is causing the Voltage-Drop.

As an example, a standard 12-gauge Building-Wire, 100-feet-long,
will have less than a ~5% Voltage-Drop at 20-Amps.

Your Voltage Drop is coming from something other than the Wire you are using.

Your measurement techniques will NOT demonstrate the cause of the Voltage-Drop.

Your setup can very comfortably use
standard, 10-gauge, Stranded, THHN-Insulated, Building Wire from Home-Depot,
and it would be difficult to accurately measure the
minuscule Voltage-Drop in that 36-feet of Wire at 20-Amps.

It will create less than a ~1% Voltage-Drop, that's less than ~0.12 Volts.

Your problem is elsewhere.
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You are measuring the "gross" voltage drop of the entire system,
but what you keep referring to is "The Wire Gauge" ............
If you want to determine the Voltage-Drop due to Wire-Resistance
then measure the actual Voltage-Drop of the Wire,
that is, connect your meter to each end of ONE of the Wires running to the Motor,
then double that Voltage number.

There is absolutely no way that you are loosing almost 10% of your Voltage,
in a huge Copper-Wire, with only ~20-Amps flowing through it.
It just can't happen that way.

You are measuring the "Voltage-Sag" of the Battery,
plus every other intermediate connection between the Battery and your testing points,
and then thinking that it's ONLY that fat Copper-Wire that is causing the Voltage-Drop.

As an example, a standard 12-gauge Building-Wire, 100-feet-long,
will have less than a ~5% Voltage-Drop at 20-Amps.

Your Voltage Drop is coming from something other than the Wire you are using.

Your measurement techniques will NOT demonstrate the cause of the Voltage-Drop.

Your setup can very comfortably use
standard, 10-gauge, Stranded, THHN-Insulated, Building Wire from Home-Depot,
and it would be difficult to accurately measure the
minuscule Voltage-Drop in that 36-feet of Wire at 20-Amps.

It will create less than a ~1% Voltage-Drop, that's less than ~0.12 Volts.

Your problem is elsewhere.

Thank you! Let me see what other data i have. I did measure voltage drop on just the positive line from battery to motor, when out of the water, so it was pulling less amps.

Its easier to measure in garage vs lake, so i cant get the amps up there. The only item between the battery and trolling motor is the breakers and any connectors. I can measure the resistance across the breakers and voltage drop.

I appreciate the replies

 

1) Try to establish a repeatable Motor Load for making measurements.

2) Charge Battery,

3) Measure Battery Voltage with no Load, and under continuous Load.
This must be measured between the Lead-Terminal-Posts of the Battery,
not the Cable-Connectors.
Write down both numbers.

4) Measure Voltage "across", or from point to point, under Load,
for every single connection or change between the Battery and the Motor.
Name these points, and write down the numbers.

It should then be obvious where your Voltage-Drop is coming from.

Something that is warm to the touch would be an indicator, BUT,
you are using very large wire which can carry away Heat very efficiently,
so using temperature may be misleading.
On the other hand, an Infa-Red-Thermometer may find the problem rather quickly.
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Post #35 repeats what I stated in much greater detail. Thus it is time to check eachtransition to see where the drop is. Of course, it might also be a string of small drops adding up.