Question about regeneration spin up after going down big hill

[jpv74]

Hello all I will make this a quick question. Recently I was going down a long steep hill and letting my truck do the engine braking. Towards the bottom of the hill my truck started to wind up like a kids toy . Is this a bad thing to use engine braking on a hybrid? Have you guys experienced this? Whats the best way for the truck to release this energy? Thanks

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[Scott Asheville]

Over the last 100 years there have been arguments about physical braking vs compression braking. Teeth have been lost. Friendships broken. Probably marriages ended.

As far as hybrid or full BEV regenerative braking, it's a no brainer to let it happen. BEVs recover energy this way and it is designed to do that. Of course, regenerative braking cannot happen if the battery is fully charged. Regenerative braking is one reason why BEV brake pads essentially last forever.

If by "winding up" you mean the transmission is kicking into a lower gear and the engine revs, well that probably goes into the first paragraph above, which is compression braking. But you have a hybrid, so I'm not sure about that. It could be some weird combination of regen and compression braking.

Somebody who knows hybrids better than me, please correct anything I got wrong. I'll come back and edit any incorrect bits out.

 

[Sticks]

It's completely normal. Your regenerative braking fully charged the high-voltage battery, so the internal-combustion engine started doing more engine braking.

The shifter should be in L for prolonged engine braking.

 

[HeyBales]

Don't overcharge a battery.

So the engine is brought in and gearing changed for it to take the energy that can't be sent to the HVB because it's already topped off.
With eCVT that gearing can be whatever is called for.

You can't mess with what's going happen, so learn the sound so you know it's alright.

ETA - engine didn't start doing more, is if it was doing any.
It was brought online at some point, it was not being used at all prior.

L won't change much - except do faster regen until the battery is full which takes less time then, and then exactly what happens above with engine.

If the normal regen your Mode was using was good for almost the entire hill until the bottom, then that much regen was available - no matter how it was obtained.
You could have pressed the brake pedal while keeping it in regen, harder.
You could have changed the Mode to Eco for more auto-regen and no braking by you.

Doesn't matter - at some point max battery charge would have been reached sooner or later, and engine would have been brought in to take some load, and your usage of the brakes or the mode usage for regen would have relied on the engine instead of battery charging, and your real brakes could have been used for more if desired.

 

[Goose201]

This happened to me on a trip last summer out to the tetons and yellowstone in my hybrid. The first time it happened, i was a bit concerned, but then eventually assumed it was the battery being full or it was the battery needing cooled down and it being cooled.

 

[Ozarkbeard]

It happens if the battery is fully charged to the amount allowed, or if the battery has not warmed up yet in cold weather. In the latter case, The HV battery will not accept a charge until it has been warmed to a certain temperature. In this case, engine braking will begin, to assist the friction brakes in slowing down.

Someone correct me if I'm wrong, but IIRC, in this case, if the ICE is not running, the engine braking will occur with the ICE remaining off.

 

[The Real Maverick]

THERE CAN BE NO ENGINE BRAKING WITH THE ENGINE OFF.

If you meant "engine on and spinning really fast without fuel" then yes, this is exactly what it does. It "runs" without fuel to "use up" excess energy.

 

[The Real Maverick]

First- coasting or braking the wheels will turn the traction motor, and the traction motor will generate power, and the power will recharge the battery. Engine can be spinning or not spinning.

Second- battery is full as allowed - with continued coasting or braking the wheels continue to spin the traction motor, and the traction motor generates power, and sends the power to the generator, which then consumes this power by spinning up the engine without fuel. 999 MPG is shown on the screen instead of "electric".

Note: at no point do the wheels turn the engine directly, so the rpms of the engine can be highly variable at any time, proportional to how much excess "wattage" is being bled off.

 

[The Real Maverick]

Hello all I will make this a quick question. Recently I was going down a long steep hill and letting my truck do the engine braking. Towards the bottom of the hill my truck started to wind up like a kids toy . Is this a bad thing to use engine braking on a hybrid? Have you guys experienced this? Whats the best way for the truck to release this energy? Thanks

It is normal for this type of vehicle. The vehicle will not be harmed and you do not need to do anything special. See some other posts above.

 

[jpv74]

Well thanks for all of the replies. That all makes sense to me now. This long hill comes at the end of a 4 hour highway drive so my battery would have been fully charged before I took on the hill. Thanks for the info folks!

 

[Fdnewbie]

If you push the brake pedal harder, the brake pads contact the rotors, and you will use more brakes and less compression braking (the engine revving will reduce). Also, always remember, never be afraid of using the brakes.

 

[Ozarkbeard]

THERE CAN BE NO ENGINE BRAKING WITH THE ENGINE OFF.

If you meant "engine on and spinning really fast without fuel" then yes, this is exactly what it does. It "runs" without fuel to "use up" excess energy.

Thanks for the clarification, despite the all caps.

 

[HeyBales]

It was hard to hear with all the spinning engines making a whine!

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