Self-Charging in the Prime

Well, I'm in Westminster, so you know exactly where I am! The approach to the Johnson tunnel is still the hardest hill I've ever found in the US to climb. 8 miles, 5-7%, no breaks, 60mph the whole way. I've done it in the fully-loaded Prime, and maintained the speed limit the whole way.

Look at this elevation profile. Starts out around 4% and then changes to a straight up 6-7% the whole way.

 

So is it better to use EV mode when going uphill or use Hybrid mode (of course have some battery depleted so when going down hill, it has a chance to recharge)? Also for those that switch to hybrid mode when entering the highway, are you concerned the ICE hasn't had a chance to warm up and you are taxing it with high speed driving?

 

Definitely HV on the big hills. It won't stay in EV on that hill anyway.

No, and you shouldn't be either. It'll use EV as necessary to let the engine warm up.

 

Dang, compared to my 2010, I was hoping for greater improvement than that. At least in slower congested conditions like my past commute.

That car commuted 34 miles round trip, starting at the maximum elevation of 500 feet, with several descents (to near sea level) and climbs along the way for almost 2000 feet gross climb. (Round trip obviously has a net change of zero.) During the great weather season -- and no full highway speed due to congestion -- it commonly achieved 72 mpg roundtrip, peaking at 76.

I was hoping that a regular Gen4 at Colorado elevations could get a considerable boost from that. But maybe there are enough higher uncongested speeds in your route to rule out a direct comparison.

 

Those all included at least some 55 or 65 zones.

 

We were really packed, too. I didn't try to maintain the speed limit. I think I was going about 50 which had me passing some people and others passing me sounding like jet planes.

@Lee Jay had exactly the right answer. Save the EV for easier stuff, but you will want to get to the top of a mountain like that with a fairly empty battery. I don't think I charged a WHOLE lot going down that particular grade on the east side of the pass, but I'm glad I had plenty of room. As for the engine starting while accelerating or at highway speed, the EV system takes most of the load while the engine warms up, mostly with an eye toward minimizing emissions, and that has the bonus of making life easier for the ICE. When you switch from EV to HV, watch your instantaneous mpg or your remaining miles of EV and you'll see what we mean.

 

According to my limited experience, the best way to use CHG mode is downhill, with an empty battery.
In such conditions the engine load is reduced due to the slope, hence the fuel consumption is not so bad.. this is especially true in cold weather because going downhill in EV means that you have to use the heat pump to warm up the cabin, with the high risk to get the end of the descent with a battery as empty as at the start.

 

I am new to this place and appreciate all the great information on this forum!

I found a great video explanation of the Prime’s functionality
Please share