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Discussion Starter #1
Regarding regenerative braking, does anyone know if the brake pads immediately kick in when you depress the brake pedal or do they only kick in when the required braking power exceeds the braking capacity of the regenerative braking system?

The reason I ask is it affects how I should drive to maximize efficiency. Supposing a light turns red in the distance, if the brake pads don't kick in under light braking, then it seems to make sense to brake early to avoid heavy braking later and losing energy through the brake pads. On the other hand, if the brake pads are used regardless, it might make more sense to coast and brake later in hopes that the light turns green.

Anyhow, this is my first experience driving a hybrid, so I appreciate any knowledge on this you can share!
 

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Discussion Starter #2
That and I'm also wondering about it for going down long downhill stretches. If I ride the brake pedal, am I simply using regenerative braking or am I using the brake pads and have to worry about the brakes overheating?
 

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Well, you're stepping out of car club area and into engineering area, but I believe regenerative brakes do NOT use the brake pads. In other words, if you just remove your foot from the accelerator while moving forward, the electric motor will begin absorbing energy (vs wasting that energy as heat if you step on the brake).

However, to your specific point, when you actually step on the brake pedal you are then using regenerative and friction brakes. I'm fairly sure the car manufacturers would not allow the consumer to step on the brake pedal and NOT engage the brakes. That would be unsafe. So you are using the brake pads in that instance but it's a combination of both braking methods. If a light changes in the distance, I actually think the answer is the same for hybrid and non-hybrid cars - a slow controlled stop is always best for the equipment.

I doubt you need to worry about overheating brakes though (unless you are coming down a mountain, not a hill). In that case, I would downshift to bring some engine braking into the mix. :)
 

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Discussion Starter #4 (Edited)
I'm fairly sure the car manufacturers would not allow the consumer to step on the brake pedal and NOT engage the brakes. That would be unsafe.
From what I've read in several places, apparently the Lexus RX and Prius both increase regenerative braking when you step on the pedal and only apply the actual friction brakes when necessary. So I'm still not entirely sure about the Crosstrek. However, I suspect that the braking capacity of the Crosstrek's electric motor is significantly less than that of the Prius.

I wonder if it's possible to figure this out somehow regarding the Crosstrek.

See:
Regenerative Brakes | Forums | Tesla Motors
Questions about the Prius Braking System
Greenlings: How do hybrids and electric vehicles blend regenerative and friction braking?
"Switching" from Regenerative to Friction Braking a Myth? | PriusChat
etc.
 

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Discussion Starter #6 (Edited)
In case anyone is interested, AWDfreak at the Club Crosstrek forum called Subaru and got this answer from them:

Brake pedal effort or travel make no difference to how the regenerative braking system operates.

The XV Hybrid uses a conventional hydraulic braking system, and is pretty much the same as the non-hybrid XV. It is not a brake-by-wire system.

In summary, off the go pedal initiates the regenerative braking, while using the brakes simply just uses the conventional hydraulic braking just as a non-hybrid XV would.
It's a little bit disappointing that energy is being wasted whenever you step on the brake pedal compared to a more advanced hybrid system like the Prius. It's not surprising though as I would think the regenerative braking capacity is much lower due to the less powerful electric motor.

This will definitely affect how I drive approaching a red light: step on the brake lightly to enter EV mode then let go and coast with regenerative braking in hopes that the light will turn green.
 

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Remember that Subaru created a mild parallel hybrid system to augment the internal combustion engine. This was not a ground-up, purpose-built, full-on hybrid designed for super-excellent fuel economy. If that is what you were looking for, the XV Hybrid should not have been your choice...

However.....if your intent was to own an affordable, reliable, eco-friendly, go almost anywhere in any conditions on any road vehicle, then you bought the right car.
 

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One thing to add regarding using the brakes: if you are to slightly press on the brake peddle, just enough for the brake light to trip yet not enough to cause the calipers to push on the disks you are getting the added benefit of having the engine shut down. This works at speeds of approx. 81kmph and under, resulting in fuel savings when going down long hills as the engine will remain off with the battery being recharged and no gas being used. It would be of greater benefit if the engine simply shut down when taking you foot off the accelerator without having to slightly press down on the brake to activate the engine shut off. I would think they could flash the ECU to allow for this added benefit(engine shutting down once foot is taken off the accelerator without the need of using the brake) and at some point I hope this update is made. I simply don't understand why Subaru didn't set the system up differently as this would seem to be of greater benefit from the fuel savings standpoint/brake wear and would add nothing to the cost. The hybrid system in the XV definitely does not have the sophistication of the 2012 Prius ( I understand this as a cost savings measure and reduced R&D time before Subaru brought this car to the market) I had before but it is a lot more versatile and overall more fun to drive.
 

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Discussion Starter #9
Remember that Subaru created a mild parallel hybrid system to augment the internal combustion engine. This was not a ground-up, purpose-built, full-on hybrid designed for super-excellent fuel economy. If that is what you were looking for, the XV Hybrid should not have been your choice...

However.....if your intent was to own an affordable, reliable, eco-friendly, go almost anywhere in any conditions on any road vehicle, then you bought the right car.
Point taken, and I definitely took that into consideration when I bought the car (which I love, by the way!). That being said, the main reason I brought up this whole issue was to figure out how to get the most efficiency out of what I have available to me. Of course, it would have been nicer if the braking system were more sophisticated, but I'm happy with what I have and understand that having a more sophisticated hybrid system would have probably led to either poorer performance or higher price.
 

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Discussion Starter #10
One thing to add regarding using the brakes: if you are to slightly press on the brake peddle, just enough for the brake light to trip yet not enough to cause the calipers to push on the disks you are getting the added benefit of having the engine shut down. This works at speeds of approx. 81kmph and under and results fuel savings when going down long hills as the engine will remain off with the battery being recharged and no gas being used.
Hmm, very interesting. I hadn't thought of that before and will have to try that out sometime.
 

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Referring to prior post - good tip - I discovered this by accident (have only had car two days) - and the display will actually show this happening - very cool.
 

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Something to further add to the discussion in terms of how the regenerative braking works: I may be wrong ( one of the previous posts on this thread mentioned that brake pressure has nothing to do with how much regen is applied) but I am convinced that lightly putting pressure not only shuts down the engine at speeds below 80kmph but also gets the generator spinning faster/ or possibly with greater power generation. The reason I say this is that even when the engine is not shutting down due to excessive speed or not being warmed up enough when pressure is put on the break peddle I hear a distinct whirring noise and a feeling of drag. This occurs with even very light pressure on the break peddle. It feels as if the regen increases more when pressure is applied than simply taking your foot off the accelerator. I know there was mention of this being incorrect from an earlier post based on a reply from Subaru but from what I'm hearing and feeling tells me otherwise. In the coming weeks I plan on installing a Scan gauge that should tell me if I'm correct. Would be interested if anyone who has being driving the Hybrid has also taken note as to my own observations.
 

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how often should hybrid brakes be replaced then?
 

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I've owned our Crosstek Hybrid for several months now, have owned a dozen cars and previously worked in electronics. I live in a city surrounded by hills, so that I can sometimes coast 2 miles or so. I bought the Crosstek hoping that despite it's AWD it could make the most of our situation. 2 wheel drive is not an option for us. The Crosstek uses a mild hybrid system that doesn't have enough power to electrically drive by itself. Others have suggested that it does not do regenerative braking with the brake pedal depressed but I'm quite sure it does. The Crosstek seems to me to be a kind of experimental model testing the technologies and the market. People aren't used to hybrids and the technology is changing rapidly. Drivers will notice that the battery gauge typically reads as less than fully charged. This is normal and intentional as the battery is used to absorb braking energy that would normally be wasted. After mild braking down a 2 mile hill my battery is usually at 100%. Some of the braking energy may be wasted as heat but most of it isn't. The Crosstek system though, can't do regenerative braking without running the engine. This does use some gas but saves it later on. A characteristic of some batteries is that they are degraded somewhat by being fully charged or discharged. Temperature is a factor as well. Electric AWD vehicles can operate with 90 mpg efficiency and zero pollution but they are super expensive right now. Building a 30mpg hybrid AWD vehicle that brings so many technologies together is a nice accomplishment. Hopefully Subaru will use the knowledge gained to make even more refined ones.
 
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