Hi,

New to the forum and have some questions about the GM full size hybrids. Had a 2000 Silverado a few years ago and loved it. Perfect with the bed for putting all sort of things in and 4wd meant I had no problems during the winter. But the milage and size in combination with the 3 door extended cab meant it wasn't ideal at the time. However with the crew cab Silverado It would be more user friendly. After checking it out I realized that the electric drive figures isn't the best. So I'm wondering if it would be possible to improve or upgrade the driveline? Bigger electric motors and more modern/increased battery capacity? The hybrid technology and especially the battery technology has come a long way since the second generation GM hybrids was introduced.
Also wondering about the 6.0 V8. What can you improve MPG wise there? The GM LS motors are one of the most tune friendly motors I would say.

Best regards

Niklas

 

Are you referencing the GM 2-Mode or something newer?

 

Referencing to the 2-Mode hybrids.

 

The two drive motor/generators in the 2-Mode are more than twice the power that the standard HV battery can provide to them.


Good luck finding anyone to "tune"

 

So you are telling me that the electric motors are theoretically able to push the vehicle to greater speeds than 30MPH, but it's the battery that's the limitation? What is the electric motors power and battery pack specs for the GM 2-Mode hybrids?

 

It is not "theory" the drive motors are very capable.


Motors are at least 60kW each.


Battery is rated below 35kW

 

if anyone is still active on this I am curious about a couple of things. I got a Tahoe Hybrid in the fall and its a great truck, mileage is pretty good on the freeway (~22mpg) but stinks around town. I haven't done a lot of testing but it seems like its mid teens. I haven't owned a conventional gas Tahoe for comparison though, maybe in slow stop and go traffic they get 10mpg lol.

Based on my research though I am seeing the same thing you mention here that the battery is really the limitation. I installed the torque app on my phone and added some formulas which was actually kind of fun. I can now see what others say which is above 60 amps the gas engine kicks in and while tracking with the app I can see the battery fills very fast while braking and also drains really fast, making it seem like its really undersized. There is a lot of wasted energy bringing this monster to a stop that we are not bothering to capture, and how can anyone get this beast moving with less than 60 amps unless you are really tolerant to irate drivers behind you. Since the current flow is related to the battery size I wonder if anyone has researched into hooking up a second battery in parallel? Would that totally confuse the computer? I don't expect it would up the 60 amp limit which is probably coded in software somewhere but could it be possible to at least charge and discharge for a longer duration?

Just curious, love the truck and sad that no one has made anything this versatile and nice looking since. My only option for a large family is a Chrysler Pacifica, which has amazing technology but my wife thinks is too ugly haha, that and I don't want to spend that kind of money.

 

Regarding the bolded/italics/underlined part, it's not undersized. It's deteriorated, and it's nearing end of life.

Nobody is pursuing this because it's not viable. 22mpg is great. Mid teens in town is great. Compare the two on http://fueleconomy.gov

The battery is not the limitation. The thing people don't see is that 100% of all motive power ultimately comes from gas. Period. No exception. The ONLY energy added is when you fill up the tank. The system is sized for optimal balance between fuel economy, power and cost. The hybrid system is nothing more than a kinetic energy recover and storage system. If your capacity is larger than the amount needed to recover the kinetic energy, then it's oversized, and you're just hauling dead weight.

The energy you put in the battery, regardless of size, will ALWAYS be ultimately from gas.

Consider this as an expectation adjustment:

Hybrid batteries lose capacity over time - a lot of capacity. It's not at all uncommon for batteries to drop to 30% of new rated capacity before they fail. Over that 70% deterioration, there is very little loss in fuel economy and is just as easily attributed to the normal economy loss associated with an aging/wearing engine.

So, if losing 70% of your battery capacity doesn't significantly impact mileage, why would doubling or tripling your battery capacity significantly impact mileage?

It won't.

Until you've expanded the capacity by 10X and you get some useful all-EV range, and you start adding electrical energy to the vehicle by charging, you're not going to get significant mileage improvements.

 

Thanks for the reply, totally agree that the only energy in the system comes from the gas in the tank if its not a plug in hybrid. The only energy available from the hybrid system comes from regenerative braking if I understand (maybe it charges a little off the gas motor but it seems negligible). My thought was such a heavy vehicle should be able to generate (I guess I should say recover since its not adding any new energy) a lot of energy but maybe it doesn't add up to much since a lot of the slowing down probably comes from friction in the tires, air resistance etc. It could be that for a vehicle of this design (big, heavy, square, large tires etc.) this is just the best you can do.

I sometimes forget that a lot of the efficiency in a Prius actually has nothing to do with the hybrid drive and more to do with the fact that its small, light, aerodynamic, has low rolling resistance tires, etc. Nowadays a comparable gas car doesn't get a lot worse mileage.

I guess for the big Tahoe if we ever expect it to use less gas we will have to hope they put it on a serious diet or create a plug in version where we can offset some of the energy demands from the gasoline to a battery (which adds weight though lol, hard to win)

 

If your city braking is too aggressive, you will be using brake pads more than Re-Gen.


Likewise on your accel pedal. You will use more gas.