Tricking the system into full regen /wo brake blending?

[cashcow]

Just wondering on any possible ideas toward tricking the system into providing full regenerative braking with out depressing the brakes? This whole regenerative brake blending thing is really not the best. If it could be more like a Tesla where full regenerative braking is available off the bat it would be best. If it could be done for B mode only that could be better as you could use D for brake blending still if it is your thing. I'm just wondering what sort of lines we should tap into and scan for what codes exactly.

I am thinking there has to be a signal sent which let's the system know the brakes are being depressed and by how much. If it is just a signal it could maybe be scanned and recorded then decoded and hopefully make use of it. I do wonder if doing this would affect the ABS? For example... is it just a code that states increase magnetic/regenerative braking by this much... or physical brakes are being depressed this much? If it is the first then it should be no issue, I think, as it is just a signal to increase the magnetic braking, but the other would likely have issues as it is a clear statement on the position of the physical brakes.

Another thing is how is this handled when you have the accelerator pressed then depressed the physical brakes with out lifting your foot off the accelerator?

 

[TonyWilliams]

Just put it in B mode.

That is maximum regen.

 

[cashcow]

Hi Tony,

Ok, I am a little confused. I have noticed that even in B when depressing the brakes some regen increases? I thought the regen system was a brake/regen blend... but is only this for D and not for B? B is max? I am sure I have seen my regen increase while in B and depressing the brakes....

 

[TonyWilliams]

Hi Tony,

Ok, I am a little confused. I have noticed that even in B when depressing the brakes some regen increases? I thought the regen system was a brake/regen blend... but is only this for D and not for B? B is max? I am sure I have seen my regen increase while in B and depressing the brakes....

The max regen is 120 amps in "B", and 60 amps in "D".

No car (that I'm aware of) throws in all the regen just because you lifted your foot from the brake pedal.

If you go down a steep enough hill, and let off the accelerator pedal, the RAV4 will generate full regen without braking.

Obviously, regen has a lot of limitations:

1) cold battery

2) full battery

3) increasing speed with zero brake application (that's why you need a hill, increasing speed increases regen up to the limits)

4) brake pedal position (additional regen will be added up to the 120/60 amp limits, if the battery is not too cold or full)

 

[miimura]

As Tony mentioned in #4, at lower speeds, even in B, the car will not use the maximum available regen. When you apply the brakes at times like that, it will apply more regen blended with the brakes.

There are good reasons that the car is programmed the way it is. If you forced more regen there would be a lot more times when you would run into traction control situations and the system is not programmed to deal with that in an elegant way. I had a situation like that where the regen cut out due to a momentary low traction situation and it was very abrupt and alarming the way it cut the regen to regain traction.

 

[cashcow]

It would still be nice to be able to control regen directly just like with the physical brakes. I see what you mean about having traction issues due to the speed and limited/lowered spinning of the wheels. Not enough spinning combined with speed = traction issues. Still it feels to me that as I drive the rav4 ev there could be more regen added at times with out having traction issues. The not so good scenarios would be rain/snow/dirty/oily road (If ever)/ etc. I personally would like to have more control over the regen amount being applied instead of 2 settings + pre=programmed pattern based on speed. The Chevy bolt's regen on demand paddle had me pretty interested, but I am not entirely sure if it is just another 'low to high' pre-set regen setting instead of an available full range for you to pick. Though after reading around it DOES sound like it is just predetermined settings.

the issue you mention is similar to this that I read sometime ago

https://teslamotorsclub.com/tmc/threads/regenerative-braking-safety-issue.52053/

I still would want to have a more direct control of applied regen. A full and complete range spectrum would be preferable for my taste instead of 2 or 3 hard settings . Perhaps control with a paddle on the column of the steering wheel like the bolt or some other easy to access approach. certainly having to go through the screen in the MS wouldn't be the best in a quick thought situation. I just don't like brake blending. If it was more like full regen application first in the first half of the brake depression then after that apply the physical brakes then that would be more to my liking. Right now as I recall at high speed the more you depress the brake the more regen you get but by then the physical brakes have already been applied a long long time ago.

If regen works just like the physical brakes if note better (Brake pads get wet and rotors get hot) then why not apply the full amount first during brake depression then use the physical brakes?

Of course like you mentioned its not so easy because maybe the batter is full (I remember this with my nissan leaf!) or the battery might be cold (Have not noticed this since I live in los angeles) but for battery full you could set a software cap on the battery so it isn't ever truly 'full' and for cold battery... why not use an aggressive battery thermal management approach so its always ready?

sorry for the long post. This would likely be a pretty complex project.

 

[smkettner]

A light touch does seem to max out the regen pretty fast in B mode.
I doubt there is much more to gain in the scheme of things.

Seems well balanced to me and allows the right foot to relax a bit instead of constantly feathering to get the right braking. Just let it coast a bit and stop tailgating where you need to get on the brakes so fast.

 

[cashcow]

Thank you I try to remain in N as much as humanly possible and try to avoid using the brakes and D + B. If not possible then I default to D then to B always trying to aim for that switch of the light. If I have to use the brakes then something went horribly wrong . Needless to say I drive slow. I just wish sometimes there was more versatility to the regen function and other things.

 

[n3ckf]

note what tony said, especially *battery temperature*.

if the battery is not above about 55F, it will not allow full regen.

So... the *best* way to use the car in the winter is have it on the charger right up till the time you leave that runs the battery heater/cooler to get it into the "right" range so that regen will work well.

I think you actually have to be charging for this to work (ie. if it finishes before you leave it will not keep the battery at the right temp by cycling the charger, it'll just sit there not doing anything). What i often do though is go out to the car 10-15 min before i want to leave, engage the cabin heater (which starts discharging the battery) and then cycle the plug so the car starts charging (which it'll do for 10-15 min which is usually enough to get hte battery to the right temp)

Since my house is up in the mountains, i often bother to do this in the winter before i'm going to leave on a longer drive where i care about range.

 

[cashcow]

Hi there thanks for the reply
I've been sleeping out of my rav4 ev for the past.... 4 or so months. I got it back sometime in July. I roll up the windows and just leave the blower on eco hi lowest setting. no a/c or heater. I believe the temp management system is on while power is on so ... my rav4 ev should be hot and ready at just about all times!

 

[TonyWilliams]

Hi there thanks for the reply
I've been sleeping out of my rav4 ev for the past.... 4 or so months. I got it back sometime in July. I roll up the windows and just leave the blower on eco hi lowest setting. no a/c or heater. I believe the temp management system is on while power is on so ... my rav4 ev should be hot and ready at just about all times!

The battery heater is only on when:

1) The vehicle is in READY
2) The pre-conditioning climate control is on (from the app or webpage)
3) The vehicle is actively charging

It is entirely possible that you have a fan going, and no battery heater.

 

[michael]

What is the objection to lightly applying the brake pedal to obtain maximum regen? How is this any worse than using a paddle?

I find the blended braking very familiar and and am happy with it.

Other EVs I am familiar with lock out friction braking for the first part of brake pedal application (Focus and FIT for sure work this way). Does the Rav not have this feature?

 

[jgblair]

Hi Tony,

I am confused. I thought that the battery heater is on whenever it is cold enough and the car is in Ready. So if you are driving when it is cold and your battery was not already warmed up before you left, the heater would be on and decreasing your range. Is that incorrect or did I misunderstand your post above?

John

 

[TonyWilliams]

Hi Tony,

I am confused. I thought that the battery heater is on whenever it is cold enough and the car is in Ready. So if you are driving when it is cold and your battery was not already warmed up before you left, the heater would be on and decreasing your range. Is that incorrect or did I misunderstand your post above?

John

The heater won't come on at all until below about 15C / 60F.

So, READY, charging, or pre-climate.... and less that 15C.

 

[cashcow]

As Tony mentioned in #4, at lower speeds, even in B, the car will not use the maximum available regen. When you apply the brakes at times like that, it will apply more regen blended with the brakes.

There are good reasons that the car is programmed the way it is. If you forced more regen there would be a lot more times when you would run into traction control situations and the system is not programmed to deal with that in an elegant way. I had a situation like that where the regen cut out due to a momentary low traction situation and it was very abrupt and alarming the way it cut the regen to regain traction.

Hi Miimura,

Would it be safe to say that the regen applied varies depending on the speed the vehicle is traveling? In other words... the odometer reading? How else would the vehicle know when to apply so and so amount of regen in a 'safe' pre-programed way? This makes sense because when I am traveling in the city the amount of regenerative force I feel is quite difference than when traveling on the highway.

It looks like the rav4 ev even at high speeds still has more regen available because when i press the brakes lightly even in B I still gain one or two or three extra regen bars @ high speed.

I wonder... if the rav4 ev bases this on the speed of the vehicle (Tire Revolutions) then changing the tire size should affect this.

Bigger tires would lessen regen
Smaller tires would increase regen

Smaller tire = odometer read higher
Bigger Tires = odometer read lower

Would this be accurate?

 

[miimura]

As Tony mentioned in #4, at lower speeds, even in B, the car will not use the maximum available regen. When you apply the brakes at times like that, it will apply more regen blended with the brakes.

There are good reasons that the car is programmed the way it is. If you forced more regen there would be a lot more times when you would run into traction control situations and the system is not programmed to deal with that in an elegant way. I had a situation like that where the regen cut out due to a momentary low traction situation and it was very abrupt and alarming the way it cut the regen to regain traction.

Hi Miimura,

Would it be safe to say that the regen applied varies depending on the speed the vehicle is traveling? In other words... the odometer reading? How else would the vehicle know when to apply so and so amount of regen in a 'safe' pre-programed way? This makes sense because when I am traveling in the city the amount of regenerative force I feel is quite difference than when traveling on the highway.

It looks like the rav4 ev even at high speeds still has more regen available because when i press the brakes lightly even in B I still gain one or two or three extra regen bars @ high speed.

I wonder... if the rav4 ev bases this on the speed of the vehicle (Tire Revolutions) then changing the tire size should affect this.

Bigger tires would lessen regen
Smaller tires would increase regen

Smaller tire = odometer read higher
Bigger Tires = odometer read lower

Would this be accurate?

I have definitely observed that more regen (more purple bars) are available at higher speeds. Also, as you come to a stop, the regen tapers to zero and the car will not completely stop without friction brakes.

To the extent that the tire size throws the speedometer and odometer out of calibration, it should have equal effect on the regen system. However, I think it would be difficult to detect the difference by the seat of your pants without putting some ridiculously small tires on the car. The torque amplification would be much more obvious. Then again, how much easier do you need it to be to peel out in a RAV4 EV?

 

[cashcow]

I have definitely observed that more regen (more purple bars) are available at higher speeds. Also, as you come to a stop, the regen tapers to zero and the car will not completely stop without friction brakes.

To the extent that the tire size throws the speedometer and odometer out of calibration, it should have equal effect on the regen system. However, I think it would be difficult to detect the difference by the seat of your pants without putting some ridiculously small tires on the car. The torque amplification would be much more obvious. Then again, how much easier do you need it to be to peel out in a RAV4 EV?

Yes we would have to put on some small tires to feel a difference. I'm not sure how the difference would feel but looking up a tire size to odometer calculator online I see the following:

https://tiresize.com/speedometer-calibration/

Going From size 17 tires to size 15 tires will make the car run at 60.44 when you odo says 65.

R15 is basically Prius size though prius can take a tire of R14 size too.

R14 would bring speed down to 58.16.

The downside of this is that you would be putting more miles on the rav4 ev because you'd be traveling at 58 but your odo will say 65. You'd eat your warranty quicker.

On the other hand! If you put on big tires you'd travel more and put on less miles on the odo.

Biggest tires I've seen on the rav4 are r22

This would make your odo show you are going at 65 but actually be traveling at 76.4! So you'd be putting on less miles in the odo for as long as you know at what you truly are traveling.

This would also raise the top speed on the rav since it is software limited to 100 in sport mode. New top speed should be 117.53!

The opposite for the smaller size r14 would be 89.48 while the odo shows "100"

Funny info: You'd need a tire size r7 to travel at 64.93 while odo shows "100" and a tire size r31 to travel at 149.1 while odo shows 100. Well, not sure if that would even be possible based on the battery pack power out put and other factors. I just thought it would be fun to share .

I find interesting that you can extend your extended warranty just by adding taller tires to your rav4 ev. The R22 give you an extra 11.4 miles for every 65 showing in the odo per hour of travel at that speed.

Unless my math is wrong for every 1200 miles you log in you will actually go 1410.41 which is a free 210.41 miles per month if that is what you clock monthly.

So say you get the 125k mile extended warranty when your rav is just about to hit 36k in the odo. If you were to drive with the size r22 tires over the course of the miles left in your rav (Should be 89k miles left) you'd actually get 104,605.41k miles instead of 89k which, unless I am wrong, is an extra 15,605.41 miles!

With r31 tires you'd go 132,695.15 miles which is an extra 43,695.15 miles!

Nice! Thoughts?


@toyota @tundra On 30" DUB Bandidos Wrapped In 255/30R30

 

[Weekdayskier]

It looks like you are confusing wheel diameter with tire diameter. 14, 15, 17 are wheel diameters in inches.

If you are trying to decrease overall weight, a smaller diameter wheel or a lighter wheel will have less momentum. This would result in faster acceleration. I may be wrong, but that same loss in momentum might actually produce less regen. The actual effects, however, would be minimal in a vehicle that weighs in at nearly 4 thousand pounds.

If you decrease the tire size, you will be running at a higher rpm. From my days of playing with 4 x 4's, a change in diameter by say 10% will change your speedometer reading by 10%. This will also result in faster acceleration, since the lever arm is shorter. For regen, you could get more revolutions, but it probably would not offset the need for more revolutions while driving.

Bottom line is this. I don't think we can improve on what the engineers originally designed in terms of efficiency. They don't just randomly choose gear ratios, which is what changing tire size is effectively doing. Engineers are very technical and calculated in their decisions.

 

[cashcow]

It looks like you are confusing wheel diameter with tire diameter. 14, 15, 17 are wheel diameters in inches.

If you are trying to decrease overall weight, a smaller diameter wheel or a lighter wheel will have less momentum. This would result in faster acceleration. I may be wrong, but that same loss in momentum might actually produce less regen. The actual effects, however, would be minimal in a vehicle that weighs in at nearly 4 thousand pounds.

If you decrease the tire size, you will be running at a higher rpm. From my days of playing with 4 x 4's, a change in diameter by say 10% will change your speedometer reading by 10%. This will also result in faster acceleration, since the lever arm is shorter. For regen, you could get more revolutions, but it probably would not offset the need for more revolutions while driving.

Bottom line is this. I don't think we can improve on what the engineers originally designed in terms of efficiency. They don't just randomly choose gear ratios, which is what changing tire size is effectively doing. Engineers are very technical and calculated in their decisions.

Thanks that sounds very well evaluated. What are your thoughts of the added benefit in stretching out your extended warranty by going up with taller tires?

 

[davewill]

Thanks that sounds very well evaluated. What are your thoughts of the added benefit in stretching out your extended warranty by going up with taller tires?

Toyota isn't stupid. If an expensive repair comes up near the end of the warranty mileage and they find you have bigger tires, they are likely to figure the amount the odometer is off and recalculate your mileage. Also, purposefully faking the odometer reading is against the law some places, and a scummy thing to do everywhere.