How I bettered my 5'ers brakes

JosephA wrote:
Like many I felt that the electric brakes on my fiver were weak and like many, set out to the internet to find an answer. Most answers were to check the condition of the shoes, magnets, etc. but the one that stood out was to check the amperage draw of the magnets. More internet searching showed that for the 12X2 brakes on the Dexter 7,000lb axles, each magnet should draw a max of 3amps @ 13.8VDC. After checking each magnet individually I found that each drew a healthy 3amps.

Thinking there was more to this I thought about how I checked each magnet. Power was applied to the individual magnet while all others were disconnected. Well what about if 2 or more magnets were tested at one time? Going for broke I measured the draw at the 7-way truck connector by manually applying full power from the brake controller and came up with 9.5amps total which was about only 80% of the expected 12amps.

After digging into the wiring a bit more I saw that the wires used from the 7-way connector back to the axles was 14awg. Was glad to see they did use a dedicated + and - for the brakes but 14awg to carry 160+ watts for a distance over 40ft? To cut to the chase I went to Lowe's and bought 45ft of 8awg stranded primary wire. I used the new primary wire for the - feed and used both of the original wires (14awg wire is about 1/2 the thickness of 8awg) for the +. Along the way I removed the crimps and soldered every connection. Now when I measure the draw at the 7-way connector I get a reading of 11.5amps and while still not perfect, there is a huge improvement in the trailer brakes. This combined with the Hawk SD brake shoes on the TV make for an absolutely incredible difference in stopping power.

Hope this helps someone.

Joseph

you found and fixed one of the major flaws in many trailer brake systems, inadequate wire size. Also, if you haven't done so check the wire size going through the axle to the far side brakes. Often it to is undersized. upgrade that with external wire run zip tied to the axle. And as a final update, ground the ground wire run from the 7 way at the frame at the front of the trailer AND back at the axle. Then tie the brake ground to the same lug. Now the ground run is in parallel with the frame, further reducing voltage drop.

Going from 14 gauge to 8 gauge cuts your resistance by a little more than a factor of 4. Each time you go down 3 sizes in AWG the resistance per unit length gets cut in half. (going up 3 sizes doubles the resistance).

the solution I did was to run two sections of #10 from the 7 way connector. One to the front axle, one to the rear axle. Then #12 to the opposite side of axle for the "outside" brake. Then again, ground the run at each end.

Before at full power (13V) I couldn't lock up the brakes on dry pavement. Now I can lock them up at 8V.