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When driving down the mountains, the battery fills up really fast. With all the bars fully charged now, it continues to show the battery is still being charged but the van makes a loud revving sound like the engine is growling(but the engine isnt running).

Does anyone know what this might be? Its very annoying.
 

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When driving down the mountains, the battery fills up really fast. With all the bars fully charged now, it continues to show the battery is still being charged but the van makes a loud revving sound like the engine is growling(but the engine isnt running).

Does anyone know what this might be? Its very annoying.
Engine braking. Very normal, computer controlled. It is "loudish", but saves some on your brake pads. I think regen braking is more effective but when the batteries are full there is no place else to send those electrons, so it switches to the friction/compression of the engine to slow you down......kind of like those annoying loud 18 wheelers using their engines for braking.
 

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One of my few gripes is the HV battery is too small. I do a lot of mountain driving and fill it up frequently and switch to engine braking. The computer controls revs so it won't hurt the engine and it saves your brakes but it can be loud, I've had it rev up to 5000rpm on steep descents. I'm mostly annoyed at all that energy I paid for in fuel getting lost.
 

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The engine braking is used to prevent free-wheeling (as if the car was in neutral). ICE vehicles in drive always have some engine braking effect when in drive and your foot is off the accelerator pedal. When regenerative braking cannot be used, the engine braking does take over. As far as I know, the braking system does not switch to friction brakes unless your foot is on the brake pedal. The only exception to this is when the cruise control is being used and it is necessary to slow the car because the car in front has slowed (or stopped). The braking system then will use the friction brakes (and will also light the brake lights when it is pressing the brake pedal for you.)
 

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The other thread about engine braking mentions that it also helps braking components stay cool. Overheated brakes have dramatically less stopping power.
This is true for ICE vehicles too, which is why automatic transmissions have almost always had an "overdrive" gear that could be disengaged or a 2/L position on the shifter, and more recently, sequential gear selection via "manual mode"
 

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Pretty sure there’s no fuel injection going on when engine braking and the engine is just acting like a big air pump being driven by the wheels.
Actually, in Toyota hybrids, it's actually the engine acting an a big air pump driven electrically by MG1. The wheels drive MG2 to generate electricity, and when the batteries get full, the electrical power is dumped to spin MG1.
EricD has a point, that if the batteries were bigger, the fuel used to get up that hill would be recovered as electrical energy and stored for later use rather than being dumped.
 

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Pretty sure there’s no fuel injection going on when engine braking and the engine is just acting like a big air pump being driven by the wheels.
Right, I've verified via odb there is no fuel burn. I was talking about the fuel burned getting me UP the mountain and gaining me gravitational potential energy. That energy fills up the tiny HV battery in a few miles and then all the rest of that potential energy I gained from fuel burn just goes to heat.
 

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Actually, in Toyota hybrids, it's actually the engine acting an a big air pump driven electrically by MG1. The wheels drive MG2 to generate electricity, and when the batteries get full, the electrical power is dumped to spin MG1.
EricD has a point, that if the batteries were bigger, the fuel used to get up that hill would be recovered as electrical energy and stored for later use rather than being dumped.
A bigger battery would certainly be nicer, but that adds cost. With a bigger battery, you could add a plug, and then potentially have 30-50 miles of EV only range. Of course, more cost. This is why EV vehicles are expensive.
 

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So this is a question is still have after nearly a year of ownership: when pressing lightly on the brakes and I can see it is charging the battery. So if I'm going down hill, I would hold the brake at 25-40% to maximize the charging. Does this actually engage the physical brakes? Or is it purely regenerative engine braking? I just don't want to be riding the physical brakes down a mountain.
 

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As long as the needle on the ECO gauge is not at the bottom and the battery is not fully charged, you are using regeneration until about 17 mph. 17 mph and below is where the friction brakes start being used as regeneration is no longer as effective at slowing the car. Note that both regeneration and friction brakes are used together.
 
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