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After I have come down a long hill and my battery is fully charged, while still on the hill and not requiring any power, my ICE comes on. Anyone know why? Seems a waste of gas when there is plenty of battery power when and if I need power. Any suggestion on how to keep this from happening?
 

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After I have come down a long hill and my battery is fully charged, while still on the hill and not requiring any power, my ICE comes on. Anyone know why? Seems a waste of gas when there is plenty of battery power when and if I need power. Any suggestion on how to keep this from happening?
I think someone said the ice is turning to help brake the car since no Regen because the battery is full. Though turning no gas is being used?
 

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This seems to be the case. Since the battery is "full", there's nowhere to store any regen. So the ICE is engaged to provide some compression braking. I personally don't feel the ICE is helping much, and would prefer the car simply switch to the mechanical brakes. Since I encounter this every morning leaving my home, I either turn off on an earlier street that lets me burn a percent of battery power, then continue down another street and gain that percent back in regen, or I just shift into neutral and coast downhill, using the brakes to slow me. One of a few things I think the engineers could have done differently.

And yes, gas is being used, because my MPG will drop from 999 while it's running, even though it's not actually powering the car at all.
 

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This is another mystery. Trying to get additional engine braking via manual downshift in Sport mode is an exercise in futility. Why then does programming force engine downshifting when the battery cannot absorb any more regen? The only reason I can think of is that the engine has variable valve timing and can improve actual engine braking. If that is the case, fuel use is virtually absent and the display change is just predicated on not being in EV mode.

Lots of reports of engine coming on when battery is saturated going downhill, but they never give enough details to suit me. I'd be interested to know if this behavior happens when cruise control is on and set to a specific speed and if the speed is maintained (a low set speed on a really steep hill would be the most interesting). Alternatively, does the engine come on when you are just "coasting" downhill with your foot off the throttle?

By the way, there is one situation I'm in almost daily where the instant mpg display is clearly screwy. I'm at the top of a short hill in EV (in my hybrid) and shift into neutral for a half mile coast to the next stop (if I leave it in gear, I cannot make it to the stop). During this period, no EV light is lit (can't be in EV as I'm not in gear". Yet before I come to a complete stop, the instant mpg is close to, but not maxed out. If the light is red, I put it back in gear, and regen immediately shows on the power meter, but EV light is still not on. As best I can tell audibly, the engine is off the whole time. I guess I could put on my OBD reader and see what engine rpms are doing to tell if it is on or off.
 

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Lots of reports of engine coming on when battery is saturated going downhill, but they never give enough details to suit me. I'd be interested to know if this behavior happens when cruise control is on and set to a specific speed and if the speed is maintained (a low set speed on a really steep hill would be the most interesting). Alternatively, does the engine come on when you are just "coasting" downhill with your foot off the throttle?
Here's my scenario. I pull out of the garage, up a 8% sloped driveway. I still show 100% as I crest the driveway (it's only about 25'). From then on, I'm coasting to a stop sign, then going down about a 12-14% grade for 1/2 mile. Other than a slight acceleration from the stop sign to start downhill, it's all foot on the brake to maintain speed the whole way down. I've never tried using the cruise going down. Just over 1/2 way down (about 1/4 mile from the garage), the engine will fire up, often quite loudly (high RPM), but doesn't really seem to add any compression braking. Once I reach the bottom of the hill and stop at the intersection, the engine will shut back off. The trip MPG, which was showing 999 at first, has dropped, but I can't recall exactly how much. If I take the car out of gear, there's no regen, and the engine does not start. I can't keep my foot off the brake, because it's too steep and I would pick up too much speed before reaching the bottom, where the road tees and I would hit a building if I went straight. :)

I found another option, which is to turn onto a slight uphill street just before I reach the point the ICE starts, travel a couple hundred yards, then continue downhill on a different street. Since I've used just enough EV power to switch roads, the ICE never fires up, and I'm back to 99% SoC at the bottom. That's what I now do most mornings, which is why I can't recall exactly what the trip MPG display says when the ICE starts. :D
 

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While I'm certainly no expert the only thing I can compare it to is the Prius. I would think they would be both engineered pretty similarly. The Prius seemed to get the battery filled more quickly than the Niro. When going down hill and the battery gets filled you can hear the engine really rev. The ICE would just be spinning to provide engine braking and the fuel would be off. Also a lot of times when you stopped (for a stop sign or light) at the bottom of the hill if the battery was too filled the ICE would spin like it was trying to start, but with the fuel off it wouldn't start. This was to take the little extra charge out of the battery. I would think the Niro may work the same but since I'm not in a hilly area anymore I've never seen the battery get close to full.
 

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One tends to notice such things on a quarter horsepower bicycle powered by vegetables. What looks flat to car drivers ... No regen either but coasting is delightful.
 
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