battery use

Don't speed. As with any car MPGs fall off fast above 65 MPH or so.

Check tire pressures at least monthly. Also, many people inflate the original tires to 42/40 PSI front/rear because it noticeably improves MPGs, but it does make the ride and handling harsher.

Don't use "B" in ordinary driving! It reduces MPGs. It's only there as an alternative to riding the brakes on a long downgrade. There's no city in the US where you need to use "B".

Driving technique short-path zen:
- Accelerate briskly (this makes most efficient use of the engine)
- Gliding (no arrows on the "Energy" display) is better than coasting
- Coasting is better than braking
- Braking is better than stopping
Figuring out how to apply those principles in real situations is an exercise for the driver.

 

It is hard to know where to start. The regen system is more efficient than gliding in certain situations. Gliding accrues an energy deficit by using the battery, so it is not a free ride. Regenerating reclaims energy that would otherwise be wasted as heat. When the car gets up to 40 mph, you have a certain amount of kinetic energy, which has been supplied by the engine. How you use that energy is up to you, and how the car got to 40 in the first place, whether by using the engine or by pushing it yourself, does not enter into the efficiency equations. Gliding is one way to try to maximize the energy use. It was developed long before hybrid vehicles were available, and works even better when you have on-board energy storage via the battery. However, gliding uses up energy via the synergy drive and the battery which will have to be replaced, so the mileage number on the display is higher than the actual mileage you will get after taking into account the battery usage.

I tried the following yesterday:

Using a cycle of two p&g and one p&c over a 15 minute time frame, I
got 73+ mpg, and only drew the battery down 2%; the 73 mpg was
close to the actual mileage, since the battery was recharged by the p&c
during the run and the draw-down was much less than normal p&g

I guess my point is that there might be better modes than p&g using the rest of the hybrid system, but we have to look for them. P&g was developed for non-hybrid cars. and there may be better ways of doing things. P&c works a lot better than would have been evident from the various posting here, and there are a lot of other modes that need to be investigated.

I want to point out that the battery is going to be charged, even if the engine has to be operated in an inefficient mode. The control system wants the battery to be 60% or higher. While the engine likes to run under a moderate load, it does not like to accelerate. Acceleration takes energy and reduces mileage. The instantaneous mileage readout will demonstrate that. If, during p&g, the control system is also recharging the battery during the acceleration phase, the overall efficiency will drop. Keeping the battery above 60% will minimize the charging-during-acceleration losses. Using a p&c periodically will also keep the battery charged. Whether it is a better mode has not been determined.

I think it is time to move on to other topics. Five pages of posting is enough.

I am headed to Burning Man this year....anyone else going?

Pat

 

I suspect a terminology problem: "gliding" (as I thought most people use the term, and as I explicitly defined it above to try to make sure there was no confusion) is the no-arrows condition, which does not use the traction battery. Your remarks apply to coasting, which does make use of the battery.

 

I suspect a terminology problem: "gliding" (as I thought most people used it, and as I explicitly defined it above to try to make sure there was no confusion) is the no-arrows condition, which does not use the traction battery. Your remarks apply to coasting, which does make use of the battery. It really is more energy efficient to avoid use of the battery.

 

You'll find, if you read through all of drysider's comments in this thread, that when he says that "Gliding accrues an energy deficit by using the battery", what he means is that since the generator is not supplying electricity to the battery while you glide, the battery is being slowly drained for the purposes of keeping the vehicle operating (powering the various ECUs, headlights, A/C, accessories, etc). With a scanguageII you can see that with a no arows glide there typically are a few amps being drawn from the battery.

Of course this power is being drawn from the vehicle even if you are generating via coast or regen braking. This is the one point I can just about agree with drysider on. If you can regen the exact amount that the vehicle is using, then you can go straight from generator to use while avoiding drawing that power from the battery. This reduces the conversion losses.

Unfortunately, even a regen coast seems to regen too much and send power into the battery. Regen braking even more so, obviously. So perhaps somewhere on the edge between glide and coast, just barely regen might be the optimal method of slowing the vehicle as far as MPG is concerned.

The best possible option as far as MPG is concerned is put nothing into the battery and take nothing out. Since this is not possible in normal daily driving, the next best is take as little out of the battery as possibe, and put back in only as much as you take out. It's the "put back only as much as you take out" that seems to have drysider stuck. He seems to find that since you have to put some back in, it is best to do it with regen braking. I agree with him only in so far as if you need to use the brakes, then regen braking is the way to go.

However, the only reason you need to use the brakes is because you needed (or wanted) to accelerate more than was necessary to glide to a stop. As such the regen power really came from the excessive acceleration, and therfore is really just using the ICE as a generator for that power and storing it temporarily as kinetic energy.

It would have been better to go straight from the generator to the batery rather than through the kinetic energy path. Using the kinetic energy storage, you expose the available energy to losses from aerodynamic and rolling friction and you have to go through the generator twice (once to convert to kinetic and again to convert back) exposing the energy to an extra conversion loss.

From what I've been reading, this is where fdrysider keeps getting lost. He seems to start his analysis at the moment the decision is made to slow down and he seems to assume that wether gliding or braking that decision is made at the same instant in time. The reason gliding is more efficient is that in order to glide, you must either be traveling slower or make your decision to slow earlier then you would if braking. Either way you've used less fuel prior to the decision to glide (acceleration to a slower velocity, or acceleration for a shorter duration).

Drysider also keeps mentioning that when you glide to a stop you've thrown all that kinetic energy away to heat meaning that aerodynamic drag and rolling friction have completely wiped out any kinetic energy you had, but then he goes on to assume that with regen you can reclaim some of that kinetic energy that would have been wiped out. He fails to realize that in order to use braking, you need to travel at a higher speed for a longer distance than if you glide. Therefore, over the same distance stop-to-stop, you'll actually increase your frictional loses with braking, not decrease them. All the kinetic energy lost during a glide is also lost during braking (and then some), but any excessive kinetic energy you've created beyond the frictional losses can be reclaimed (less some conversion losses). The point of gliding is to not create the excessive kinetic energy in the first place.

 

Quick question what dose the ECO button do?