Trailer talk: Brake controller settings

[idoco]

Curious what settings people are using for their brake controllers and how they arrived at those settings?

Talking to a few people it seems as if the regen allows for a much lower assist setting. At least compared to what you would get following the manufacturer's recommended instructions.

 

[ohmman]

Good question.

I have my Prodigy P2 set at 3.0, mostly hoping to lose as little energy as possible to heat and braking. My goal is always to recapture as much as possible using regen.

I had a very unscientific method of turning that up to about 6.0 when driving through mountains and turning it as low as 1.0 in city environments. I haven’t done the latter again as just managing speed and deceleration has the same effect without the potential danger of underbraking.

I’m interested to hear the experience of others.

 

[qadaemon]

Tekonsha Prodigy P3 set to 4.5 for the double axle camper, and basically off for the single axle flatbed utility trailer. Haven't hauled a substantial load larger than a few sheets of plywood on that though.

 

[Big Earl]

As regenerative braking is controlled by the accelerator, you should be able to configure your trailer brakes for the best, most balanced braking performance without worrying about losing too much energy due to friction braking (as long as you don't use the friction brakes unnecessarily).

 

[qadaemon]

As regenerative braking is controlled by the accelerator, you should be able to configure your trailer brakes for the best, most balanced braking performance without worrying about losing too much energy due to friction braking (as long as you don't use the friction brakes unnecessarily).

The hard part with adjusting the brake controller--at least on my older X--is the controller uses the brake light rather than the brake pedal as an input (it also uses it's own accelerometer). The brake light is often on during regen without the brake pedal being pushed. I'd like it to use minimal trailer brakes under regen without the brake pedal pushed and more trailer brake with it pushed. I can do it manually by setting the controller for low gain, then pull the boost lever while using the pedal, but that has its own issues.

 

[ohmman]

The hard part with adjusting the brake controller--at least on my older X--is the controller uses the brake light rather than the brake pedal as an input (it also uses it's own accelerometer). The brake light is often on during regen without the brake pedal being pushed. I'd like it to use minimal trailer brakes under regen without the brake pedal pushed and more trailer brake with it pushed. I can do it manually by setting the controller for low gain, then pull the boost lever while using the pedal, but that has its own issues.

Correct me if I'm wrong, but I believe the Prodigy (and other proportional brake controllers) use deceleration and not the actual brake light to signal trailer braking. This is a reason mounting direction and levelness is so important on the controller. It is sensing the movement of the vehicle. My controller display shows braking independent of the X brake lights, so I feel pretty certain that's how it works.

Perhaps you have a different type of controller.

 

[Big Earl]

The hard part with adjusting the brake controller--at least on my older X--is the controller uses the brake light rather than the brake pedal as an input (it also uses it's own accelerometer). The brake light is often on during regen without the brake pedal being pushed. I'd like it to use minimal trailer brakes under regen without the brake pedal pushed and more trailer brake with it pushed. I can do it manually by setting the controller for low gain, then pull the boost lever while using the pedal, but that has its own issues.

Ah yes - that would definitely eat into a lot of regeneration.

 

[qadaemon]

Correct me if I'm wrong, but I believe the Prodigy (and other proportional brake controllers) use deceleration and not the actual brake light to signal trailer braking. This is a reason mounting direction and levelness is so important on the controller. It is sensing the movement of the vehicle. My controller display shows braking independent of the X brake lights, so I feel pretty certain that's how it works.

Perhaps you have a different type of controller.

I wonder if that's a difference between the P2 and P3? I think it uses brake light as an input for its calculation along with the accelerometer, but I could be wrong.

I'm assuming that from a couple behaviors I've noticed/become annoyed with: If I tap the brakes to kill cruise control but still hold the same speed with the accelerator, the controller applies the trailer brakes for a second or more even though the car is not decelerating. It also turns on & off trailer hold rapidly while reversing. I think I push the brake pedal right at the spot where the lights flicker while parking, which turns it on and off rapidly. Both of these occurred on the truck I had previously with the same model controller installed. On the X, I leave the controller in the glove box most of the time, so it "forgets" I disabled trailer hold once I unplug it. Very annoying.

 

[ohmman]

I wonder if that's a difference between the P2 and P3? I think it uses brake light as an input for its calculation along with the accelerometer, but I could be wrong.

You are not wrong. I was mistaken. I checked the pinout for the controller harness and it looks something like this:

Black: +12V power
White: Ground
Blue: To trailer brake (via 7-pin)
Red: Stop Lamp input

So the controller receives a signal when the vehicle's brake lights have illuminated, and proportionally controls via the reading from the internal accelerometer.

I swore that I'd seen the controller come on even when my lights weren't on, but I guess that's just an artifact of middle age.

 

[ecarfan]

Correct me if I'm wrong, but I believe the Prodigy (and other proportional brake controllers) use deceleration and not the actual brake light to signal trailer braking. This is a reason mounting direction and levelness is so important on the controller. It is sensing the movement of the vehicle....

I was mistaken. ...So the controller receives a signal when the vehicle's brake lights have illuminated, and proportionally controls via the reading from the internal accelerometer.

Just to help me understand this discussion: it appears that it is not necessary to mount the controller so that it is perfectly level (or very close to perfectly level). Correct?

This page for the 90885 Prodigy P2 states “No level adjustment necessary - it adjusts itself to varying terrain as you drive”
. Tekonsha!

 

[qadaemon]

You are not wrong. I was mistaken. I checked the pinout for the controller harness and it looks something like this:

Black: +12V power
White: Ground
Blue: To trailer brake (via 7-pin)
Red: Stop Lamp input

So the controller receives a signal when the vehicle's brake lights have illuminated, and proportionally controls via the reading from the internal accelerometer.

I swore that I'd seen the controller come on even when my lights weren't on, but I guess that's just an artifact of middle age.

You know, I have a P2 on my stick-shift Wrangler TJ; I'm pretty sure it brakes the trailer when downshifting/engine braking even if I'm not on the pedal. We're likely both technically correct--the best kind of correct!

Just to help me understand this discussion: it appears that it is not necessary to mount the controller so that it is perfectly level (or very close to perfectly level). Correct?

Yes, within reason. It can't be mounted vertically for instance. The P3 is almost horizontal in the X, and the P2 probably 30-ish degrees in the Wrangler. Both work just fine.

 

[adelman]

I wonder if that's a difference between the P2 and P3? I think it uses brake light as an input for its calculation along with the accelerometer, but I could be wrong.

According to Tekonsha the Prodigy P2 and P3 both have the same behavior; the difference is in the screen and diagnostic abilities.

There is no magic number for trailer brake setup. You need to test tow your trailer fully loaded, at about 25mph, and while coasting apply maximum brakes using the manual lever on the brake controller. The trailer brakes should NOT lock up causing the trailer to skid. The idea setting for safety/stability of the tow is to have the trailer stop itself, and that occurs with the highest setting that will not skid the trailer. This setting will increase with increased weight in the trailer, and decrease in conditions that decrease traction (like rain).

If you run a setting LOWER than this, you're letting the cars brakes/regen do more of the work. You're trading safety to get efficiency. You WILL have longer stopping distances. As someone who almost stuffed his Model X into a car in front of him (because I had just loaded a trailer and pulled out of a loading dock and hadn't yet adjusted the controller) (to make matters worse, the car in front was pulling another trailer I owned!), I wouldn't make this trade.

I'll point out that for freeway driving (minimal braking and regen opportunities), reducing the setting sacrifices, high speed stopping distance for minimal gain. If you want to do this, the time to do it is in city driving, low speed, lots of regen. Might as well just leave the brake controller off.

If you want to "compare settings", I think the number to compare is the ratio of how you set the controller to the "skid point" (the setting just lower than the point where you can skid the trailer tires with manual trailer brake application).

As someone who retrofitted brakes onto a 1200# trailer, I can tell you that I would never make this trade.

 

[idoco]

while coasting

Coasting as in shift to neutral or coasting as in remove foot from accelerator and let regen kick in?

 

[adelman]

Coasting as in shift to neutral or coasting as in remove foot from accelerator and let regen kick in?

Shouldn't matter. Even if the brake controller is kicking in during the regen scenario, it should be very lightly and the lever will override that and go to a higher braking voltage, which is what you're trying to check. As long as you keep the vehicle moving at approximately 20-30mph during the test.