How to improve the electric brakes

dieselengineer said:

So I pulled in a set of number 12s in addition to the stock wiring.

Click to expand...

Not sure what you mean. Sorry.

Chuck

12 gauge wires?

I was on my previous trailers forum and this rewiring of the brakes was a thread. They also ran heavy wire but also mentioned was that they said the wires should be the same length to all the magnets. Since I don't consider myself an electrical wizard whats your thoughts on wire length for equal amps-volts to the brakes?---Ken

No expert here by any stretch Ken but that seems to make sense. My understanding is with electronic brake controllers is that they send a voltage to the brakes that is proportional to the amount of braking being done on the tow vehicle.

If I am close on that, and if the total circuit resistance for each side of the trailer was not similar (i.e. different lengths of wire, different gauges of wire, corroded electrical connections etc.), the side with more resistance could receive a lower voltage and apply less braking than the side with less resistance.

This is just me thinking this through out loud and may not be how these braking systems really work.

Sounds like we need to hear from some of our resident experts. Chime in boys

Jim

I certainly am no expert either, but I think the difference you may see if the wires were slightly different in length would be minimal. Voltage drop is really an issue with long runs. If your wire to the right side was 12" longer I don't believe you would ever know it in performance. Now 30' is a different story. So using the original posters measurements you are probably looking at .07 of a volt drop in a foot of wire approximately.

The whole concept is an excellent one and I would agree worth doing, but I would not be overly concerned about the exact length. Actually if I recall right the wire goes to one wheel then to the other, I don't believe there is a wire for the right side and one for the left. So if you wanted to equalize the braking I would run the wire to the opposite side first.

Voltage drop is much greater with low voltage than with high voltage, and dc current drops faster than ac also.

I would love better brake response, where did you tap in the 12's? I have never traced the system back to the source

Before running extra wiring to the brakes, I would recommend checking voltage to each brake with the emergency break-a-way pin removed and RV connected to shore power. This will duplicate normal driving condition with the batteries charging. The voltage at each wheel should be the same as the RV battery voltage. If not, the wiring between the hitch pin and wheels needs attention.

To check voltage when connected to TV, have engine running and the manual brake controller lever pushed to the full braking position, if 12 volts at the wheels, the wiring is sufficient, if not, the controller and/or wiring may have a problem.

When adjusting each brake, pull the emergency break-a-way pin to measure voltage and verify the brake will lock-up the wheel. All wheel brakes should have the same voltage.

I was told that if the break away pin is pulled while the tv is connected that it would fry the controller, sound right?

Uncle Rog said:

I was told that if the break away pin is pulled while the tv is connected that it would fry the controller, sound right?

Click to expand...

Roger,

Negative...............the controller will not fry if pin is removed. Several of us have had the pin pull out during travel when the cable was pinched in the hitch during a turn. The only thing that fried was my brain until I realized why I was having trouble moving during a left turn at a road construction area. Some of the other inconvenienced drivers may have fried a little.

Forrest

I fried my ego after I learned that I didn't break my break-away switch but that I had already nipped the wires close to the switch. Oops.

Jim

diesel,

What was the voltage gain running the #12 wires to the magnets vs the 10 volts via the factory wiring under the same battery supply conditions?

Forrest

Jim and Forrest, thanks for telling your stories on yourselves! Ha...

Oh geeze, like I need another project.

I copied this from the alco axle paperwork I have.

System voltage is measured at the magnets by connecting a volt
meter to the magnet lead wires. Connect the trailer wire connector to
the tow vehicle. The engine of the tow vehicle should be running. The
voltage should start at 0 volts. As the controller bar is slowly actuated, it
should gradually increase to about 12 volts. If the increase is not
gradual the brakes would apply instantaneously. The lower the
threshold voltage the smoother the brakes will apply.
System amperage is the amperage being
drawn by all brakes on the trailer. Single
magnet amperage can be measured with an
ammeter attached at the magnet lead wires.
Follow procedure above. Each magnet should
draw about 3 amps at 12 volts. To check the
total system the controller output to the brakes
must be disconnected and the ammeter put
into series in the circuit. With magnets cold
(70o F), the ammeter should read about 3
amps for each brake or 12 amps for a tandem
axle trailer (4 brakes). (Amperage is affected
by the length and gauge of wire between
ammeter and brake as well as between the
power source and brakes.)

So I found a voltage drop calculator on line and with 14 ga wire and a 25 ft one way run the drop is nearly 16%.
12 ga reduces the drop to 10%
10 ga the drop is a little over 6%
8 ga drops to just under 4%
6 ga is about 2.5%
well you get the idea.

Here is the calculator I used http://nooutage.com/vdrop.htm

So,...... looks like I got another project.

I went back and researched the SOB site and this is what other info I found. They use Dexter on this brand and Dexter recommended a minimum of #12 wire , which was not present on these trailers. They were replacing with #10 wire and stressing to make solder connections on the install . The problem areas were the connections at the magnets and insulation wearing off the wires running inside the axle, to much wire inside the drum rubbing on brake parts and corrosion at the crimped wire locations.
This has been great info guys, this is what the forum was meant for, like my DW says I need all the help I can get. ----Ken

I am using a BrakeSmart brake controller.

BrakeSmart controllers are capable of indicating volts and amps on the display. This takes the guess work out of the brakes electrical condition. Mine is indicating 13.4 volts with engine running and 9 amps at full braking. BrakeSmart Tech advised the amps should be 12 amps for maximum braking. The reason for only 9 amps is because the existing wiring (#12 or #14) is to small causing high resistance. They recommend #8 from hitch-pin to center of axles and continue #10 to brake magnets. However, they did say that the 9 amps is sufficient under normal conditions and full braking (12 amps) may never be required. Full braking with 12 amps could result in brakes locking up, which not a good thing.

I am going to leave things the way they are, with over 20k miles towing I never felt the need for more trailer brakes.

Those of you moving 11 tons down the road should really consider the brake controller. $400.00 for the best is a small price to pay considering the risk.