SwedeSpeed - Volvo Performance Forum banner

1 - 20 of 39 Posts

·
Registered
Joined
·
658 Posts
Discussion Starter · #1 ·
When going down a long hill, especially on the highway, I've always just shifted down into B mode to give the battery some juice thanks to good old gravity.

But someone told me that it's more efficient to use the center display left panel to switch to Charge mode instead.

Does anyone know if there is an appreciable difference?
 

·
Registered
Joined
·
110 Posts
Manual says Charge activates the combustion engine. Is that what you want to do?

Install the Owners Manual on your mobile phone, it's very easy to search for a subject matter.

What might be interesting to understand is, at what point do the friction brakes engage over the regenerative braking, which could allow you to charge faster when going down a steep downhill.



Sent from my SM-G955U using Tapatalk
 

·
Registered
Joined
·
78 Posts
As I understand it the shifting to B recovers kinetic energy generated by momentum and gravity whereas setting the vehicle to Charge mode turns on the ICE generator which charges the battery using gasoline.

If the battery is depleted in the scenario you describe, ICE is on anyway and idling as you coast down a hill. This result in high MPGs for any ICE. Turning on the onboard generator will lower those MPGs but not appreciably. B mode would, from seat of the pants experience, only augment that charge.

If the battery is already at half to 3/4 charge or higher, engaging the ICE generator does not give much bang for the buck and I’d stick with B mode.

FWIW, I use power mode on uphills which turns on the generator and under normal driving partially mitigates the huge drain of an uphill climb. I use an individual mode (pure with hybrid ride height) and B on the downhill. If the battery is lower than half, I’ll also turn on Charge.

I’ll never forget a trip up to the mountains I took where I stopped at the base for lunch, charged for about 45 minutes while I stopped and ate. Gained a little more than a quarter charge and when I started the climb, in hybrid mode, the charge was gone in about a mile or so. Been using power mode ever since for hill climbing, even at low speeds.

If anyone has technical knowledge about the subject I wonder if B on a downhill plus Charge actually powers up the battery faster or if Charge is already the maximum input.


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
6,912 Posts
Long downhill with B mode works same as "Charge" mode as long as ICE doesn't engage.
In B mode, it will try to use battery and stop ICE when possible. This is fine as long as you don't want to keep the battery for later use.

Don't over-think it. As long as energy is not wasted you are efficient.
Following wastes energy:
- Hard braking that engages mechanic brake
- Using ICE to charge battery
- Using ICE at low speed or stop-and-go traffic

I would love to have a few miles of battery range for the city street driving of my trip. So when possible I'd just use battery "hold" at a few miles remaining, and switch to Pure mode to use the last 2 battery miles at end of trip.
 

·
Registered
Joined
·
3,640 Posts
When going down a long hill, especially on the highway, I've always just shifted down into B mode to give the battery some juice thanks to good old gravity.

But someone told me that it's more efficient to use the center display left panel to switch to Charge mode instead.

Does anyone know if there is an appreciable difference?
Regenerative braking (B) is more fuel efficient than using ICE every time (I.e., No fuel v. Fuel even while idling).

If you want to charge with your engine, charging downhill is more fuel efficient than uphill or level.

If you combine both Regenerative Braking and Charging while going downhill, it seems that one could charge faster.

With that said, I have experimented with the charging with ICE. It does not take long to go from an indicated “0%” hybrid charge to 25% in about 15-20 min. which can be enough for limited local during on the end of the trip. I also found that trying to charge between 75%-97% takes a longer time to avoid overcharging the hybrid battery. I am assuming that last point. I don’t do the 75-97% anymore.

If I do want to charge on level ground, I typically wait until I am up to speed. Charging at 60 mph is more fuel efficient than at 75 mph.

Lastly, I use Pure almost all of the time and ACC when it makes sense. I use charging via ICE minimally and I use Hold almost all of the time on the open road while trying to retain 50-75% charge for dense and/or local traffic. I seem to get much better overall fuel economy in that configuration.

Anyway, I have hoping for three years that there were more documented best practices from an engineers and Volvo.


Sent from my iPhone using Tapatalk Pro
 

·
Registered
Joined
·
1,921 Posts
When going down a long hill, especially on the highway, I've always just shifted down into B mode to give the battery some juice thanks to good old gravity.
Continue doing that. If you drive in HYBRID/PURE mode downhill, ICE will shutoff as well. :)

Burning gasoline to turn a generator (charging your battery) is less efficient that burning gas to propel your vehicle.
 

·
Registered
Joined
·
3,640 Posts
Continue doing that. If you drive in HYBRID/PURE mode downhill, ICE will shutoff as well. :)
That is great to know. I have hardly ever driven downhill.


Sent from my iPhone using Tapatalk Pro
 

·
Registered
Joined
·
129 Posts
I totally expected a "negative" conversation based on the title. lol.
 

·
Registered
Joined
·
251 Posts
Hot tip for long highway downhills, keep it 75MPH or lower.

If you stay under 75MPH, the larger electric motor in the rear axle can still regenerate power, and also the ICE can stay off (don't turn on Charge or Power mode, let the ICE turn off!). WAY more power regeneration and MPG extension that way.
If you let the vehicle creep above 75, then the ICE starts up and even if it's not burning fuel you're still throwing away energy through pumping losses, and you only have the smaller crank driven front electric motor/generator to scavenge electricity.
 

·
Registered
Joined
·
664 Posts
How is the re-gen braking on the T8? On Tesla’s it’s very aggressive (or can be setup in that way). By aggressive I mean, as soon as you lift your foot off the accelerator, the car almost comes to a complete stop, without using the mechanical brakes. Guess that’s why Tesla’s hardly ever need brakes replaced?
 

·
Registered
Joined
·
3,640 Posts
How is the re-gen braking on the T8? On Tesla’s it’s very aggressive (or can be setup in that way). By aggressive I mean, as soon as you lift your foot off the accelerator, the car almost comes to a complete stop, without using the mechanical brakes. Guess that’s why Tesla’s hardly ever need brakes replaced?
I cannot compare a T8 to a Tesla since I have never driven a Tesla.

With that said, the “B” gear selection is for more aggressive re-gen braking. I would say it is at least moderately aggressive - but compared to what?

In “B” gear, once your foot comes off of the accelerator the re-gen braking starts immediately. It can bring you to a stop but you would tick off the drivers behind you well before then.

While in “B” gear, as soon as you touch the brake pedal, re-gen starts the braking. As more pedal pressure is applied, up to a point, the more aggressive re-gen becomes. However, if you apply hard enough pressure, the mechanical brakes will be applied. This is indicated by the four orange ticks at the bottom of the re-gen scale.




Sent from my iPhone using Tapatalk Pro
 

·
Registered
Joined
·
1,158 Posts
I pretty much only drive the car in B range. I find the regenerative aspect somewhat weak when compared to our Chevy Bolt. With the Chevy Bolt you can drive with one foot as the regenerative braking can be aggressive enough to bring you to a complete stop and hold you there. It is also adjustable with a tab on the steering wheel. I would like the Volvo to have more aggressive regenerative braking but do not see it as too much of negative at this point. I find that I enjoy the Power mode so much that I am often only in that mode (still with the B on). On occasion if on a short trip I will use the hybrid mode. There are probably some hype milers out there who can adjust on the fly for the terrane and speed.
 

·
Registered
Joined
·
6,912 Posts
I prefer to use brake to regenerate as my foot can stay on brake pedal for more time. In case of quick braking is needed, my response will be much quicker than moving foot from gas pedal to brake.

I never got the idea of single pedal driving. It is a risk to safety, and not saving anything for your foot.
 

·
Registered
Joined
·
658 Posts
Discussion Starter · #14 ·
So apparently I was right, and B mode is the best thing to do going downhill. I have very rarely used Charge, just a couple of times when I was out of battery and wanted some for the end of my trip in the city.

Thanks to everyone who responded.
 

·
Registered
Joined
·
411 Posts
yes ty.....learned more about the T8....99% of my driving so far has been 20 miles to work...charge battery....20 miles back.....so stay on PURE mode and on battery....
 

·
Registered
Joined
·
50 Posts
B can be less aggressive if the battery is full or cold (beginning of the trip) but I can’t imagine an escenario where Charge could be more efficient but I’m too lazy too make the math and tell exactly by how much.

Like fusionRed said, if you can put the right pressure in the brake it could be similar to going in B, but you would loose some regeneration for the time where you switch from the gas to the brake pedal (it can’t be too many watts).
 

·
Registered
Joined
·
664 Posts
I cannot compare a T8 to a Tesla since I have never driven a Tesla.

With that said, the “B” gear selection is for more aggressive re-gen braking. I would say it is at least moderately aggressive - but compared to what?

In “B” gear, once your foot comes off of the accelerator the re-gen braking starts immediately. It can bring you to a stop but you would tick off the drivers behind you well before then.

While in “B” gear, as soon as you touch the brake pedal, re-gen starts the braking. As more pedal pressure is applied, up to a point, the more aggressive re-gen becomes. However, if you apply hard enough pressure, the mechanical brakes will be applied. This is indicated by the four orange ticks at the bottom of the re-gen scale.




Sent from my iPhone using Tapatalk Pro
This answers my question perfectly. Tesla’s are pretty aggressive on regen braking, but it sounds like the T8 does a good job of not using the mechanical brakes too much. Thanks for the info, now I got to drive a T8 to compare, but it sounds pretty good.
 

·
Registered
Joined
·
3,640 Posts
How does using ACC affect mileage?
The relationship of using ACC to fuel economy is mostly antidotal as I have not tried nor am I qualified to do any scientific study.

With that disclaimer, ACC seems to optimize regeneration of hybrid charging on a T8 including charging. It also seems to manage acceleration and regenerative braking more smoothly under normal conditions.

Anyway, that’s what I think but no one has shared any evidence either way.


Sent from my iPhone using Tapatalk Pro
 

·
Registered
Joined
·
7 Posts
How is the re-gen braking on the T8? On Tesla’s it’s very aggressive (or can be setup in that way). By aggressive I mean, as soon as you lift your foot off the accelerator, the car almost comes to a complete stop, without using the mechanical brakes. Guess that’s why Tesla’s hardly ever need brakes replaced?
The T8's regen braking is much more subtle than my husbands Tesla S. I hardly notice it in the T8, where in the Tesla it was quite uncomfortable until I got better at using it.
 
1 - 20 of 39 Posts
Top