Regeneration and Brake Lights

Every once in a while we get this topic intermixed on other threads.

The blogosphere has been active in this arena ever since the crop of new EV owners 'discovered' regeneration, with some of the most active threads being on the Volt hybrid forum where they beat this topic to death.

The issue is to ensure that gentle deceleration does not prematurely produce a 'nuisance' brakelight but that significant deceleration does indeed light it.

There is even a UN(!) performance-based specification for this area http://www.unece.org/fileadmin/DAM/t...gs/R13hr2e.pdf

5.2.22.4. Electric regenerative braking systems as defined in paragraph 2.17., which produce a retarding force upon release of the accelerator control, shall generate the signal mentioned above according to the following provisions:
Vehicle decelerations Signal generation
≤ 0.7 m/s² The signal shall not be generated
> 0.7 m/s² and ≤ 1.3 m/s² The signal may be generated
> 1.3 m/s² The signal shall be generated
In all cases the signal shall be de-activated at the latest when the deceleration has fallen below 0.7 m/s² 8.

Even though I would like more regen in 'B', I'm quite content with Mitsubishi's implementation, and I believe our i-MiEV falls in the lower and middle range of this spec, with our regen still too weak to require the brakelight activation; nevertheless, it behooves all of us to simply be aware of traffic behind us and use the brake pedal if we think a slowdown warning is advisable.

If anyone is paranoid over this, there are third-party add-ons such as this one which flashes during severe braking (I know nothing about this product, just found it Googling):
http://safelightstore.com/smart-safe-LED-brake-lights.html

With accelerometers now being standard on most (all?) new cars, software implementation of this can be readily done by the manufacturer so in the future I would hope to see greater regen options on EVs. Having four levels of regen (including N) was one of the main reasons I chose the i-MiEV.

It's never been much of an issue with me - I've driven manual transmission cars all my life and have always done the majority of my braking by downshifting. I sold a Toyota Supra that I put 165,000 miles on and advised the new owner that the brake pads Toyota put on it at the factory were the ones still on the car

I guess if you are the type who isn't always aware of what's happening behind you, then this could be a problem, but I keep a close eye on the mirrors even when I'm not slowing

Personally , I'd like to see the CHMSL give a flashing warning of cars slowing and not using the brakes - Maybe flashing at a rate proportional to the deceleration - Keep the brake lights for use only when the brakes are applied

Don

I feel B regen is significant...significant enough that it should engage the brake lights. D and E, I would say no. BUT...nobody listens to me.

I agree with fjpod that there should be lights in B mode. Around Pittsburgh, people almost hit you just coasting. I have to put it in neutral, push the pedal for lights with the turn signal on, then go back to Drive to keep from getting hit turning into work.

Years ago, back in the days when they had six taillights, I saw a Chevrolet "idea" car that had different colored taillights. When driving with your foot on the accelerator you would have two green lights showing in the rear, foot off the acceleartor and not on the brake, two yellow lights and finally foot on the brake two red lights. I always thought that was kind of a good idea (except if you were color blind). I have driven cars with regenerative braking for some time now and just keep an eye on the rearview mirror. If there is someone following I apply enough pedal pressure on the brake pedal to get the brake lights on. Using engine braking in a manual transmission ICE car can give a lot higher rate of decelleration then our regen modes so the same rule applies when I am driving them. It's just a lot harder to downshift when slowing and get the brake lights back on.

siai47 said:

I have driven cars with regenerative braking for some time now and just keep an eye on the rearview mirror. If there is someone following I apply enough pedal pressure on the brake pedal to get the brake lights on.

Click to expand...

Very well said siai47. That's exactly what I do too.

I drive in B mode all of the time and rarely need the friction brakes. Having done this for several months, I have come to firmly believe that braking is braking and should illuminate the brake lights. The driver behind me needs to know that I am decelerating and doesn't care how.

I would appreciate any ideas on how to get the i-MiEV to illuminate the brake lights during regenerative braking.

-- Art Z.

In addition to the link in my first post, you might see if these guys got off the ground after their Kickstarter crowdfunging: http://vololights.com/ There are a number of gadgets for bicycles; for example (I don't know if they went into production) http://www.lucidbrake.com/, and I'm sure some googling will uncover more.

We all understand what you're saying, but if you've ever followed a skittish person who rides the brakes you quickly realize how distracting and aggravating it would become if every deceleration turned on a brakelight - which is why there are performance-based specifications for this (with which I believe the i-MiEV complies). For myself, I'm always tuned in to cars around me and simply use my brake pedal for regen if needed.

<rant> As an example and off-topic, but related to lighting, I consider DRLs to be a disservice to motorcycles. Whereas DRLs have a legitimate place on two-lane roads for safety, I consider their proliferation and continuous use by cars in multi-lane traffic to no longer have the attention-drawing aspect that motorcycles with headlights ON enjoyed for many years. Light pollution, to its safety detriment.</rant>

azemon said:

. . . . I have come to firmly believe that braking is braking and should illuminate the brake lights. The driver behind me needs to know that I am decelerating and doesn't care how.

Click to expand...

If that was the case, then brakelight switches should be mounted under the accelerator pedal on every car ever built, because unless you're going down a steep hill, you're slowing anytime your foot isn't on the accelerator

I think that would be a huge step backwards. As it is now, many 'two-footed' auto trans drivers are going down the road intermittently flashing brakelights so often that you're pretty much forced to ignore them and then when they actually do begin to slow, it comes as a surprise to everybody - We sure don't need any more cars giving us 'false alarms'. I think there needs to be a 'standard' for how much deceleration requires a light and how much doesn't . . . . like in the link Joe posted

I would appreciate any ideas on how to get the i-MiEV to illuminate the brake lights during regenerative braking.

Click to expand...

I've bought some pieces to tinker with to make this happen - Haven't had the time to play with then yet

What you need is something to measure the current sent back to the battery during regeneration and then select some level of current (which represents some level of regenerative braking) to trip a relay to light the light(s). The charge/discharge needle buries itself in the blue at around 50 amps, which is not very much braking - You can get that amount regenerating in 'D' or 'Eco' and it's pretty similar to just taking your foot off the gas in a manual trans car. Something on the order of 75 amps of regen would be a likely level to think about lighting s light . . . . either just the CHMSL or the brakelights or both

Don

Don said:

What you need is something to measure the current sent back to the battery during regeneration and then select some level of current (which represents some level of regenerative braking) to trip a relay to light the light(s). The charge/discharge needle buries itself in the blue at around 50 amps, which is not very much braking - You can get that amount regenerating in 'D' or 'Eco' and it's pretty similar to just taking your foot off the gas in a manual trans car. Something on the order of 75 amps of regen would be a likely level to think about lighting s light . . . . either just the CHMSL or the brakelights or both

Don

Click to expand...

Yup. That's exactly what I want.

-- Art Z.