Re-Wiring the brakes.
My 35' ~10,000 lb GVWR trailer brakes were wired with 14 gauge wire and very poor crimps. All the crimps on that I've seen so far are pretty bad... I'm going to redo it with a quality crimp tool ...
Forum Discussion
RCMAN46 writes "This forum and others have a lot of bad information on how a modern proportional inertia brake controller such as the popular Prodigy P2 and P3 works.
These controllers are not zombies. "
They ARE "zombies", they can not and do not COMPENSATE FOR ANY WIRE RESISTANCE between the controller and brake magnets.
You set the max output voltage and that IS THE MAX the controller can output. These controllers use PWM outputs and basically they do not output any more voltage than the input source and actually they output slightly LESS than the input voltage (13.8V battery voltage is gonna get you 12.8 or so max pulse AT THE BRAKE CONTROLLER NOT AT THE BRAKE MAGNETS).
"They are in fact very sophisticated computer controlled devices that work very well.
The controller will very the current output to the trailer dependent on the amount of deceleration the controllers inertia detector sees. This is the feedback the controller gets."
Like I stated, these controllers do not ADD voltage ABOVE THE BATTERY VOLTAGE to get the MAXIMUM BRAKING POWER (making up for wire resistance, hence the reason MANY folk can not get the brakes to lock up during the setup phase of installation..
"With a sound trailer brake system that can be set up as per the manufacture's instructions that does not require maximum gain it will not make any difference if the trailer wiring is 14 gauge or 10 gauge. The gain setting basically makes this compensation."
14ga wire IS NOT a "sound trailer brake system", 14ga wire creates a very large voltage drop.
Controller cannot provide full 12V to the brake magnets if there is a lot of WIRE RESISTANCE.
The P2 and P3 "gain" control only controls up to the battery voltage and NOTHING MORE.
The "boost" settings are nothing more than the controller IMMEDIATELY applying a percentage of the PRESET max output ("gain") to the brakes BEFORE the controller is able to calculate the actual deceleration and also does not add extra voltage ABOVE the battery voltage to compensate for high wire resistance.
"The overall maximum current seen with 12 volts at the brake magnets
is about 12 amps. 14 gauge wire can more than handle 12 amps."
14 ga wire will have enough resistance that you WILL NEVER achieve 12A and therefore you WILL NEVER ACHIEVE the maximum brake capacity.
It isn't about current handling but more of an issue of line resistance vs the magnet resistance.
For a moment think of the magnets as resistors.
Each magnet will be approx 4 ohms and resistance in parallel divides by the quantity of resistors in parallel.
so QTY of FOUR 4 ohm resistors in parallel will give you 1 ohm of resistance.
Wire has a certain amount of resistance per ft based on the wire ga size..
You NEED to take into consideration not only the + wire but the ground wire also since BOTH wires have resistance.. So in our example we will take a 25ft wire run and double the run to 50ft..
18 ga wire resistance per ft .00639 50ft .3195 ohms
16 ga wire resistance per ft .00402 ohms 50ft .201 ohms
14 Ga wire resistance per ft .002525 ohms 50ft .12625 ohms
12 ga wire resistance per ft .001588 ohms 50ft .0794 ohms
10 ga wire reststance per ft .001 ohms 50ft .05 ohms
8 ga wire resistance per ft .00064 ohms 50ft .032 ohms
2 pairs of 10Ga per ft approx .0005 ohms 50ft .025 ohms
Resistors in SERIES you ADD the resistance together..
18 ga wire at 50ft plus magnet resistance of 1 ohm (FOUR magnet coils in parallel) you will have line resistance of 1.395 ohms and max current to the magnets as 8.6 A wire voltage drop is 3.4V! You get about 72% of max possible brake power a loss of 28% due to wire resistance..
18 ga 50ft + four magnets 1.3195 ohms 8.6A 3.4V loss due to wire 28% reduction in brakes
16 ga 50ft + four magnets 1.201 ohms 9.99A 2V loss due to wire 16% reduction in brakes
14 Ga 50ft + four magnets 1.12625 ohms 10.65A 1.3V loss due to wire 11% reduction in brakes
12 ga 50ft + four magnets 1.0794 ohms 11.12A .88V loss due to wire 7% reduction in brakes
10 ga 50ft + four magnets 1.05 ohms 11.43A .57V loss due to wire 4.7% reduction in brakes
8 ga 50ft + four magnets 1.032 ohms 11.63A .37V loss due to wire 3% reduction in brakes
2 pairs of 10ga 50ft + four magnets 1.025 ohms 11.71A .29V loss due to wire 2.4% reduction in brakes
So if we use the baseline of 14Ga wire which in our example has a loss of 11% and upgrade to two pairs of 10Ga wire we would now only see a 2.4% loss which IS an improvement of 22% of your braking power!
A 22% improvement will allow you to reduce your brake controller output!
A 22% improvement in braking power over 14ga is no chump change and is well worth the time and expense..
Now about this time folks are wondering why not just add second 14 ga pair..
Well you could, however one trailer I found SIX FACTORY non outdoor splices between the tongue and first axle, and ALL the splices were badly weather damaged. The cheapskate factory decided to use a bunch of factory floor cuttings on my trailer.. that should have been tossed out.
You ARE better to forget about the factory 14ga wire and run new HEAVIER wire and get the job done right.
These controllers are not zombies. "
They ARE "zombies", they can not and do not COMPENSATE FOR ANY WIRE RESISTANCE between the controller and brake magnets.
You set the max output voltage and that IS THE MAX the controller can output. These controllers use PWM outputs and basically they do not output any more voltage than the input source and actually they output slightly LESS than the input voltage (13.8V battery voltage is gonna get you 12.8 or so max pulse AT THE BRAKE CONTROLLER NOT AT THE BRAKE MAGNETS).
"They are in fact very sophisticated computer controlled devices that work very well.
The controller will very the current output to the trailer dependent on the amount of deceleration the controllers inertia detector sees. This is the feedback the controller gets."
Like I stated, these controllers do not ADD voltage ABOVE THE BATTERY VOLTAGE to get the MAXIMUM BRAKING POWER (making up for wire resistance, hence the reason MANY folk can not get the brakes to lock up during the setup phase of installation..
"With a sound trailer brake system that can be set up as per the manufacture's instructions that does not require maximum gain it will not make any difference if the trailer wiring is 14 gauge or 10 gauge. The gain setting basically makes this compensation."
14ga wire IS NOT a "sound trailer brake system", 14ga wire creates a very large voltage drop.
Controller cannot provide full 12V to the brake magnets if there is a lot of WIRE RESISTANCE.
The P2 and P3 "gain" control only controls up to the battery voltage and NOTHING MORE.
The "boost" settings are nothing more than the controller IMMEDIATELY applying a percentage of the PRESET max output ("gain") to the brakes BEFORE the controller is able to calculate the actual deceleration and also does not add extra voltage ABOVE the battery voltage to compensate for high wire resistance.
"The overall maximum current seen with 12 volts at the brake magnets
is about 12 amps. 14 gauge wire can more than handle 12 amps."
14 ga wire will have enough resistance that you WILL NEVER achieve 12A and therefore you WILL NEVER ACHIEVE the maximum brake capacity.
It isn't about current handling but more of an issue of line resistance vs the magnet resistance.
For a moment think of the magnets as resistors.
Each magnet will be approx 4 ohms and resistance in parallel divides by the quantity of resistors in parallel.
so QTY of FOUR 4 ohm resistors in parallel will give you 1 ohm of resistance.
Wire has a certain amount of resistance per ft based on the wire ga size..
You NEED to take into consideration not only the + wire but the ground wire also since BOTH wires have resistance.. So in our example we will take a 25ft wire run and double the run to 50ft..
18 ga wire resistance per ft .00639 50ft .3195 ohms
16 ga wire resistance per ft .00402 ohms 50ft .201 ohms
14 Ga wire resistance per ft .002525 ohms 50ft .12625 ohms
12 ga wire resistance per ft .001588 ohms 50ft .0794 ohms
10 ga wire reststance per ft .001 ohms 50ft .05 ohms
8 ga wire resistance per ft .00064 ohms 50ft .032 ohms
2 pairs of 10Ga per ft approx .0005 ohms 50ft .025 ohms
Resistors in SERIES you ADD the resistance together..
18 ga wire at 50ft plus magnet resistance of 1 ohm (FOUR magnet coils in parallel) you will have line resistance of 1.395 ohms and max current to the magnets as 8.6 A wire voltage drop is 3.4V! You get about 72% of max possible brake power a loss of 28% due to wire resistance..
18 ga 50ft + four magnets 1.3195 ohms 8.6A 3.4V loss due to wire 28% reduction in brakes
16 ga 50ft + four magnets 1.201 ohms 9.99A 2V loss due to wire 16% reduction in brakes
14 Ga 50ft + four magnets 1.12625 ohms 10.65A 1.3V loss due to wire 11% reduction in brakes
12 ga 50ft + four magnets 1.0794 ohms 11.12A .88V loss due to wire 7% reduction in brakes
10 ga 50ft + four magnets 1.05 ohms 11.43A .57V loss due to wire 4.7% reduction in brakes
8 ga 50ft + four magnets 1.032 ohms 11.63A .37V loss due to wire 3% reduction in brakes
2 pairs of 10ga 50ft + four magnets 1.025 ohms 11.71A .29V loss due to wire 2.4% reduction in brakes
So if we use the baseline of 14Ga wire which in our example has a loss of 11% and upgrade to two pairs of 10Ga wire we would now only see a 2.4% loss which IS an improvement of 22% of your braking power!
A 22% improvement will allow you to reduce your brake controller output!
A 22% improvement in braking power over 14ga is no chump change and is well worth the time and expense..
Now about this time folks are wondering why not just add second 14 ga pair..
Well you could, however one trailer I found SIX FACTORY non outdoor splices between the tongue and first axle, and ALL the splices were badly weather damaged. The cheapskate factory decided to use a bunch of factory floor cuttings on my trailer.. that should have been tossed out.
You ARE better to forget about the factory 14ga wire and run new HEAVIER wire and get the job done right.
