Re-Wiring the brakes.

+1 Gdetrailer

My 5th wouldn't lock on loose gravel with the original wiring. I did some improvements and increased total current by about 1 amp. This was enough to lock easily on hard-packed gravel and almost lock on pavement. Big difference.

Main wires give the biggest improvement. The long wires that cross by the axles will give you a very slight improvement. Changing wires to individual magnets is not worth the effort.

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.

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 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.

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.

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.

As for the wiring becoming a fuse the Prodigy controller will not output more than the gain setting even with a dead short. This would be about 12 amps with a maximum gain setting which a 14 gauge wire can handle continuously.

Bottom line if you want to rewire with 10 gauge do so. If you are going to rewire the trailer I still suggest a separate run for each side and eliminate the troubled wiring in the axle tubes.

But if you are having brake problems 10 gauge wire may not correct the problem. There are many more factors that need to be considered first.

mrekim wrote:
What is the issue with the twin contact style? The TV pin goes between the contacts and makes a connection on both sides.

With a single contact, I guess the TV pin would press against the single blade on one side and the plastic connector on the other side.

Am I missing something?

Yes you are missing the fact that the cumulative insertion force is well over 300ft to insert the twin contact style terminals. The inserted connector will only have <1mm of contact.
The low contact insertion will result in a connector that is not stable during use between the vehicles. Intermittent connections and vehicle warnings will occur from normal vibration and stress applied to the cable.
The other problems are dimension alignment of the terminals in the over mold. Bargeman doesn't use a premold to hold the terminals during over mold process. The terminals will move during the injection of the rubber and cause misalignment. This will cause even higher insertion force.
The flat blade style terminals will have 9-10mm of insertion contact. This will hold the connector securely during use.
Just upgrade to the flat blade style terminal and leave all of these problems behind.
MM49

What is the issue with the twin contact style? The TV pin goes between the contacts and makes a connection on both sides.

With a single contact, I guess the TV pin would press against the single blade on one side and the plastic connector on the other side.

Am I missing something?

mrekim wrote:
I'm working up a parts list now....

BenK wrote:

I'd get a NEMA 4 junction box with a 30amp minimum terminal block mounted on the
inside. That TB needs to have 'U' jumpers to tie several terminals to become the
hot and ground...plus the control lines for the rest of the trailer

Right now there's a 4" galvanized box on the tongue. It's a standard "in the wall" electrical box. At some point that box will have to go, but I'm going to leave it for the time being. I plan to terminate everything into that box.

So the work in that box will be:
1) Convert everything to ring terminals
2) Remove the two 6 gauge wires and twist nuts and replace with 10 gauge and ring terminals
3) replace the 1 14 gauge pair for the brakes with 4 14 gauge pairs.
4) Add terminal blocks for the ring terminals.






My current thought is to get a few 65Amp terminal blocks. The only reason for the 65 amp version is that they have #10 screws vs #8 so I can torque them down tighter. I have to get 4 circuit versions in order for them to fit in the box. I'm hoping that 4 will fit reasonably well - 2 on the back an one on the top and one on the bottom.


All the wires will get marine grade (heat shrink with glue) #10 ring terminals.

You might as well upgrade the whip to your vehicle. Make sure that you get one with the blade style terminals in the trailer side. Don't use a Bargeman twin contact style. Twin contact terminals will not work with you tow vehicle. The very best whip on the market is a Hopkins flat blade style with tin coated terminals. Pollack makes a nice assembled whip with Sanoprene soft wire.
MM49

I'm working up a parts list now....

BenK wrote:

I'd get a NEMA 4 junction box with a 30amp minimum terminal block mounted on the
inside. That TB needs to have 'U' jumpers to tie several terminals to become the
hot and ground...plus the control lines for the rest of the trailer

Right now there's a 4" galvanized box on the tongue. It's a standard "in the wall" electrical box. At some point that box will have to go, but I'm going to leave it for the time being. I plan to terminate everything into that box.

So the work in that box will be:
1) Convert everything to ring terminals
2) Remove the two 6 gauge wires and twist nuts and replace with 10 gauge and ring terminals
3) replace the 1 14 gauge pair for the brakes with 4 14 gauge pairs.
4) Add terminal blocks for the ring terminals.






My current thought is to get a few 65Amp terminal blocks. The only reason for the 65 amp version is that they have #10 screws vs #8 so I can torque them down tighter. I have to get 4 circuit versions in order for them to fit in the box. I'm hoping that 4 will fit reasonably well - 2 on the back an one on the top and one on the bottom.


All the wires will get marine grade (heat shrink with glue) #10 ring terminals.

It's only going to be as good as the weakest link in this food-chain and that will
be the connector between the TV & trailer

I'd get a NEMA 4 junction box with a 30amp minimum terminal block mounted on the
inside. That TB needs to have 'U' jumpers to tie several terminals to become the
hot and ground...plus the control lines for the rest of the trailer

Then from that point you can decide spider (wagon wheel with it the hub and the
points the spokes) or one big lead 'back' there

Make sure to use ring lugs and NOT spade lugs.

If you don't have lots of experience crimping lugs...practice, practice...

Suggest buying your connectors in large, contractor quantities. Especially
if you are going to be working on your own stuff. I also buy'm on sale
so the per connector cost many times is less than half of list.

Here is one of my electrical setups when doing the harness for my
Suburban


I no longer own a trailer, but borrow often. Some allow me to update
their's when I've decided going to borrow often.

I use a #10 AWG with a ring lug to their trailer end of the connector
Then run one #10 AWG wire 'back' there and then split it to both sides.

Since not mine and they won't pay for the install...just a 'thank you'
I don't put a NEMA 4 box back there. Just water proof the splice

Good point on including return wiring. I redid the math. 16G "home runs" are slightly worse than a single 10G run and 14G home run is slightly better. The voltage at magnet for 16,14,10 respectively are: 12.18V, 12.40V, and 12.27V. Double 10G would result in 12.51 to each magnet. All from a 12.8 volt source.


I'm not too worried about the new wire shorting out. It will be placed in a wire loom, that's part of redoing the job correctly. If the magnets short out, the 18G wires coming from the magnet will act as a fuse. I would hope they would melt back until there was an open circuit. Hopefully the brake controller would see the additional current draw an warn with an overload. I haven't had this happen and the instructions for mine indicate that an overload warning exists, but does not provide details on when that alarm would fire.

Here's the in order from "Best" to "Worst" for upgrade options:

1) Dual 10G - either 1 per side or one for front axle and 1 for rear axle. Junction at axle to split off from 10G wire.

2) Home run 14G. Junction at TV plug junction.

3) Single 10G to axles. Junction at axles.

4) Home run 16G. Junction at TV plug junction.


I'm still leaning towards #2 because I like the home run idea.

mrekim wrote:
Here's a nice voltage drop calculator:


http://www.bulkwire.com/wireresistance.asp

Assumptions:
12.8 Volts at battery
4 Ohm per magnet
25 foot cable run


1 10G case:
If the 4 magnet are at the end of 1 10G wire run the the wire "sees" a 1 ohm resistance.

Wire Resistance: .04054.
Voltage at magnets : 12.3 Volts


4 16 G case:
In this case, since there are 4 wire runs, we use 4 ohms as the resistance at the end of the wire.

Wire Resistance: 0.10211
Voltage at magnet: 12.48

So, it appears that home running 16G wire would produce a somewhat better result than running 10G and then a star configuration from there.

I've simplified things and ignored the star at the end of the 10G wire. I'm hoping that simplification isn't skewing things too much...

[ EDIT ]

I redid the math and assumed a 20' run of 10G and then 4 5' runs of 10G. I got 12.52 volts to each magnet that way. So it still seems that, in theory, I would get the same results as as 10G wire.

I also looked for a 2nd way to check my math. The cross sectional area of the 10G wire is 5.26 mm and 16G is 1.31 mm. Well 5.26 / 4 = 1.315, so it appears that 4 16 gauge wires is electrically the same as one 10 gauge.


[ / EDIT ]

Your resistance assumptions need to be doubled since the ground return MUST be terminated at the front of the trailer.. And the ground wire resistance will be the same as the plus wire. Both resistances add together..

So instead of 25ft of wire it is now 50 ft of wire and your resistance from that wire is now double.. Hence the reason as to why going to at least 10 ga wire IS better and doubling up on 10 ga is even better yet..

Additionally any 16 ga wire used will become a "fuse" so to speak if just one of the 16 ga wires (or magnets) happen to short out. A short on the 16ga wire will eventually cause the insulation to melt or burn..

16 ga wire in a very short distance like from the magnet coil to the outside of the drum back is ok since the distance is short and possible damage is minimal..