Well, finally had a few free minutes today, so once I was done bolting in "Corey's Big Boy Seat Mod" to raise the front of the seats for better thigh support I had a chance to try out another mod I've been curious about. I will give a detailed version below, or just skip to the end for the summary.
The issue:
Most literature states that light braking kicks in the regenerative braking system with the hydraulic brakes kicking in when more braking is required. In reality, the Insight uses a fairly standard hydraulic braking system such that even under light pedal pressure, the hydraulic system is slightly actuated. The percentage of regenerative braking versus mechanical braking is dependent on how deftly the operator can touch the brake pedal. But even in the best circumstances, there appears to be a slight drag from the mechanical brakes.
In the quest for maximum efficiency, one would need to have pure regenerative braking (and supply the battery pack with the maximum amount of recharging). The regenerative system needs to be triggered independently of the hydraulic system. This brings the question, "what triggers the regenerative mode in the first place?" I had suspicions that the regen may be triggered by nothing more than the actuation of the brake lights as many cars already use a signal from the brake lights to disengage the lock-up torque converter in an automatic transmission.
To test this theory I performed the following procedure:
Materials required - two lengths of 14-16AWG Wire, 1 SPST Momentary switch Normally Open, basic soldering equipment
To get started I stripped ~1/2 inch of insulation off of each end of the two lengths of wire. Solder one length of wire to each terminal of the switch and "tin" the loose end of each wire with solder. Follow the cars brake pedal up to a switch. This is the switch that actuates the brake lights. It should have a connector with a black/white wire and a pure white wire facing the aft end of the car. Insert one end of the tinned wire alongside each factory wire. This is commonly called "backprobing" If you are a contortionist, you do not even need to pull the plug. The wires can also be removed with no permanent damage to the car. Once the wires are inserted and secure, turn the key to the "on" position and press the switch...the brake lights should illuminate. If not, double check the connections. Locate the switch in a convenient location.
In operation, when driving down the road and regenerative braking is desired, simply depress the switch. Your brake lights will illuminate to caution other drivers of your slowdown and the regenerative braking system only will be actuated. This insures that every watt of power is delivered to the battery instead of being burned away as heat at the brake rotors. If at any time you desire more braking the hydraulic brake pedal can be depressed as normal.
Testing - I took a ~5 mile drive through mixed traffic and a short trip on the highway. The modification did not set any codes or appear to affect any systems in a negative manner. So the good news is that it appears to work, and should be fairly failsafe. If the switch were ever to fail to close, you simply will not get regenerative braking until you step on the pedal (system will revert to normal operation as it will if you simply don't press the installed button) If the switch were to stick in the closed position, regenerative braking would be applied, however, you could simply disconnect the installed wires to revert to normal operation as well.
In summary, hooking a momentary switch in parallel to the brake light switch would give the user command of "100% regenerative braking mode" However, I can not vouch for the amount of savings this would generate...in theory it would probably be pretty small. But so is the investment in parts and labor.
Pretty clever. Can you tell a difference between regen only, and light pedal pressure? In other words, how much braking force does regen by itself have?
It may be me, but I feel like I can trigger regen only with light braking, but as you say, the brakes are mechanical (hydraulic) and should move if the pedal is moved.
I would probably use this trick on a particular long decel to an off-ramp I drive every day. But I wouldn't actually need the extra charge, as I rarely drop the SOC more than 1 or 2 bars in my usual driving.
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2000 #893
LMPG 73.3, same speed too
By "seat of the pants" it "seemed" like the car did not brake as hard by just pushing the button (although all bars on the charge indicator were lit) as it would when I tap the brake. (This would seem to indicate that, at least for me, the hydraulic brakes are slightly applied during regen mode)
If you are Fred Astaire on the pedals, you can probably hit the very "sweet spot" where the regen is kicked on but the hydraulic brakes aren't on too much. But me, clonking my size 13's around on those postage stamp sized pedals...maybe I tend to stab it a little harder. This mod is definitely scrounging the last few percent of economy. But the price is pretty cheap!
Willie:
I would expect that all the safeguards that apply when you tap the pedal would still apply when you use the button. All you are really doing is fooling the electrical system into thinking the brake pedal has been depressed while the hydraulic system thinks it has not yet been activated.
As Holicow pointed out, some people may be able to balance on this sweet-spot naturally. Another option could be to adjust the stock brake switch in or out to trip the regen at the earliest possible moment.
I just felt this was a quick, cheap, and easy way to insure that the car is making the maximum use of regen. It would seem to be especially helpful for drivers who routinely coast down for a long distance, or big footed people like me!
Also of note, I had hoped that the button might also act as sort of a "forced charge" setup where one could press the button to go into regen, then apply the accelerator at the same time. However, this does not appear to happen. In my test, when I held the button in and set up regen, then depressed the accelerator, the charge indicator swung into the "assist" range.
That's a neat idea. I'd considered something like that, but I didn't realize that it could be so simple to implement! Is there any way to your knowledge to "regulate" the amount of regen you get? Or will that method only give maximum regen?
As per the assist coming on with the gas, I think that someone made mention of that in a thread a couple of weeks ago. I believe the speculation was that the throttle control took precedence (or at least has a lot more numerical "weight" than) the brake control.
I just know I'm going to do this little mod in the next few days. Great idea!
Hmmmmmmmmm... so the brake lights come on but there is no loss of speed... this is also a great way to get rid of tailgaters without risking a rear-ender...
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Driving on down the road in my 2001 CVT, going "Boogety Boogety" ...and until avatars are provided, my car looks just like the original silver Insight on the header, above... =)
That is an interesting question...every time I pushed the button, the regen went to maximum...unless the engine speed was low, then the charge started dropping with speed.
boogetyboogety:
I wouldn't say there is "no" drop in speed...the regenerative braking does slow the car a bit. But you can be assured that 100% of the vehicles deceleration* is due to regen, not to the hydraulic brakes.
*Note: I'm saying 100% due to the regen, this is neglecting all other frictional forces which would be present under hydraulic braking as well.
Nice job Corey,
I took the lazy way out and backed
off on the brake light switch adjustment
(aprox 1/3 turn) so taking the play out
of the pedal with your foot would do
same(easy to feel). Like your mod
alot better. Where did you decide to
put the switch?
Jack Lee
Of course, you're right. Not "no" deceleration, but "very slight." Gotcha.
Which brings up a thought on my Rostra cruise-equipped CVT. I just know pressing your button will kick off my cruise control... ready for me to resume speed by pressing the Res/Accel cruise button . I've always disliked that the only real way to get out of cruise (while maintaining the speed memory) is to lightly stab the brake pedal with this setup... which only has the Set/Coast and Res/Accel buttons, but is missing that "middle" button that allows getting out of cruise without tapping the brake pedal. Or pressing both buttons at once, which shuts off cruise but eliminates the speed memory.
Ooooh, I'm going to like my Corey Button* even more now...
*Officially named in honor of you-know-who
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Driving on down the road in my 2001 CVT, going "Boogety Boogety" ...and until avatars are provided, my car looks just like the original silver Insight on the header, above... =)
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Corey's "Max-Regen" Brake Mod
