Hey,

So I recently bought my wife a 2017 Accord Hybrid EX-L. This last weekend, I took it to North Carolina on a short ski trip. I noticed that when the car is in brake mode, the brake lights are illuminated. My other car is a Nissan Leaf EV, so I understand how braking mode works and what it accomplishes. The Leaf does not light up it's tail lights in brake mode. The Accord replaced a VW TDI, which I drove in the mountains previously, and in that car, we used the Sport mode or the manual-auto shifting to downshift the car to slower speeds on descents.. the point being that I know how to drive in the mountains and brake mode is a critical function for that type of driving.

So I was driving down the mountain on Saturday night with the transmission selector in Brake Mode. I was all alone on a dark patch of road and noticed that the third (center) tail light was illuminated. Confused, I checked in the side mirrors and all three tail lights were glowing brightly. I brought the car to a stop, switched to Drive (normal) mode, and applied/released the brake pedal -- sure enough.. applying the brake pedal illuminated the tail lights the same way. I was shocked by this.. And I believe it is completely wrong (poor design).

Brake Mode regenerates electricity.. but the more important purpose is to slow the vehicle on long descents. It behaves almost exactly like putting a conventional vehicle in Low gear..

Why does it matter about those brake lights?

Well, when you drive down a long descent, you must slow the vehicle using the engine to avoid overheating and damaging the brakes. In normal vehicles, the driver downshifts and only uses the brakes to further slow (or to stop a vehicle in an emergency). If your brake lights are lit continuously, it confuses drivers in following vehicles. Eventually, they ignore your tail lights and assume that there is a malfunction or you just suck at driving in the mountains. They also become desensitized to the tail lights and start following normally. If that lead car as to stop (say that a deer steps into the road), then the lead driver slams on the brakes -- which elicits no change to the tail lights in the Accord Hybrid since they were already illuminated by Brake Mode. This is very dangerous.

So your car is already illuminating the tail lights and has no additional signals or warnings when you really do apply the brakes.

I called the 1-800 customer care number to open a ticket on this. I'm not in the mountains much, but I do go up a couple times a year. The fact that brake mode triggers the tail lights makes me look like an idiot and annoys the drivers in cars behind me. If I get rear ended in a emergency stop situation, I would definitely bring Honda into the accident situation (as in litigation).

So the message to Accord Hybrid owners is -- when you are in brake mode, and the car is being slowed, then your break lights are on. If you drive in areas where brake mode is necessary on big hills, be aware that other drivers will think you are riding the brakes all the way down. And more importantly, that applying the actual brakes will not trigger any additional illumination.. so you might get hit in an emergency stop situation.

To any Honda engineers who read this.. I would ask.. why if I put a conventional Accord in Low Gear, no tail lights, but if I put the Hybrid in Brake Mode, the tail lights illuminate? Surely there must be a way to turn this off? It is occurring due to a specific setting in the software. I presume the guy who coded it has never driven in the mountains.. sigh.

Annoyed mountain operator.

 

Brake mode does not equal low gear though. In a low gear, if given no acceleration, and on a continuous decline, the engine revs will slow until an equilibrium is reached an no more braking will occur. With B mode on in the Accord Hybrid, you will slow continuously (or at least until the battery is fully charged, not sure what happens then).

As a side note, brakes overheating will be less of an issue in the regular drive mode because the Accord will only use the friction brakes if you need significant braking or if the battery is full.

 

Thanks for the reply. I'm hoping that a Honda person is out there on these boards.. it's a long shot I know..

If you put the Accord Hybrid in Brake Mode and drive down a long enough hill that the battery maxes out, the car then engages the wet clutch connecting the gas engine and lets the wheels turn the dormant engine. The first time it happened, I looked around the dash trying to figure out what the sound was. The power transfer diagram did not show the engine turning, but I can't think of anything else it could be. At that point, if I touched the brakes, there would be no regen.. only the conventional friction brakes. In function, on hills, brake mode is equivalent in function to 'Low' on conventional automatic transmissions. You are right, it does regen, but in the mountains, the more critical function is to slow the vehicle to a manageable speed while avoiding cooking your brake pads and disks.

Having the brake lights on for this prolonged period under circumstances when other vehicles operate in low gear is just wrong. It is also potentially dangerous as it eliminates the driver's ability to warn trailing vehicles of an imminent (or emergency) stop.

Another disappointment of mine (and I knew it going into the purchase) is that the Accord Hybrid effectively uses the gas tank as a means of storing energy. The 1.3 KWH battery is woefully inadequate for anything but the shortest of electric-only operations. When you drive up a long steep hill, the car immediately goes to the gas engine and to maintain proper speed, the engine races quite loudly. The electric motor is driving the car, and the gas motor is powering the electric motor (this is by design). But the small battery is exhausted quickly on climbs. Conversely, on long descents, the battery is fully charged almost immediately, and the car reverts to dragging the inert gas motor to control speed. Drawn to the natural conclusion of climbs and descents, the car cannot store enough energy in the battery on the descent to help much on the next climb. In that sense, it is less efficient than it could be if it had more battery.

Overall, the Accord works well in day-to-day flatlander driving. I can get 50+ mpg driving modestly in my surface road commute. For my trip to NC, we drove over 600 miles and used around one full tank of gas. So the car works well under normal circumstances. But that small battery and dependence of gas->electric propulsion under load makes the car less than ideal for use in the mountains. 99% of my driving is flatland stuff, so the car is fine.. But I wouldn't recommend it for someone who lives or spends a lot of time driving in the mountains.

I'm kind of hoping that I can find a Honda representative on one of these boards, since I think the tail light - brake mode link is a software one and we might be able to change it with a minor tweak.

Thanks for your input. Hope the information I provide helps other Accord Hybrid owners to recognize the limitations of the vehicle.

Still annoyed mountain operator

 

This is definitely NOT the case with my 2017 Accord Hybrid, and I am 100% certain it is not the case with any Accords. So definitely not a "design issue."

Being in B does not bring the brake Lights on in my car.

I recommend you engage the emergency break all the way up, start the car, put it in B, make sure it is not moving, get out and check. No brake lights on in my case, driving or parked.

 

I think it might be based on how much g forces are being applied by braking, so the light will come on over a certain amount of braking force being applied. That would make the most sense.

 

It would make more sense than coming on all the time, but I don't think it would be right to do so at all. You can see the 3rd brake light when it illuminates from the rear view mirror, and it has never come on when in B.

 

I own a 2017 Honda Accord Hybrid. When driving at night, I can look in the rear view mirror to see when if my center brake light is illuminated.

Sometimes in foothill areas of Atlanta, I have used B-mode to reduce my speed. I have never seen the brake lights on when I pull my foot off the accelerator.

 

If you're already braking, and then start braking harder, your tail lights don't change.

I don't see this as an issue.