Prius c's battery should store 3x energy

I'm sticking to not much charging. I know the battery level must be maintained, therefore the engine will come to the rescue if necessary, but it would seriously degrade mileage if a significant portion of the total power output were to go into the battery and back out again.

In another thread, someone claimed to have connected a large power inverter to the hybrid battery of their Prius to power their house. They claim that the ICE kicks in to supply all the power needed. I don't doubt this at all, because it's very important for the system not to allow the main traction battery to become depleted. But this is a bit of a crisis-situation for the Prius. It's not the normal mode of operation.

 

It's a given that all Prius energy comes from the gas tank, directly or indirectly, so the issue is how efficiently it's used, including keeping the traction battery charged. There is much discussion around regen, coasting, pulse and glide etc, but their contribution is modest at best.

In a low speed / low load situation the car will go into EV, and the traction battery will be depleted to 40% SoC. At this point the ICE kicks in, mainly to boost SoC. This is not a rescue situation - it is a normal mode of operation for anyone whose miles are covered mainly in town.

In a moderate steady-speed / low load situation (above 42 mph) the car will predominantly use heretical mode. Momentum allows MG2 to generate and feed MG1, which over-drives the ICE, allowing the ICE revs to drop to about 1200, and reduce fuel consumption. SoC is steady at 60%, the traction battery is just about un-used, and the energy flow is efficient.

At higher speeds and/or load MG2 is needed to help drive the car, so energy from the ICE allows MG1 to generate and feed MG2 in turn, while still maintaining the traction battery. There is a delicate balancing act here to keep the ICE revs as low as possible, while not using the traction battery too much. The bulk of the energy flow is from MG1 to MG2 directly, not via the battery.

At very high speeds / heavy loads MG1 will reach maximum output, and traction battery SoC will start to fall. If this is prolonged, SoC will reach a minimum and the traction battery will cease to contribute - performance will be degraded, and mpg low.

Most of the time, the prius protects its battery from excessive charging by directing energy by the most efficient path. However, in the very light load situation where EV is possible, in the interests of very high mpg presumably, low SoC is allowed, then followed by substantial ICE use, mainly to boost the battery level.

 

Well you are consistent.

I think we've been over this before and others have supplied better insight than I originally did.
Power from the wall for a PiP being a whole different matter................
Near to 100% of the energy used in a hybrid vehicle comes from the ICE and the gas it burns.
If you are talking about regen braking, that recaptured energy was originally supplied by the ICE during acceleration.
If you are talking about regen coasting down-hill, then that energy was originally supplied by the ICE while going UP-hill.

There is no "free lunch" and absent solar cells or a cord to the wall, ALL of the expended energy comes from gasoline........unless maybe you
have a 40 MPH tail wind, which is pretty much a free boost.

 

I'm not sure where the argument lies. We both agree that the engine charges the battery when necessary. It's just basic physics that in order the get high mileage numbers, the system must minimize conversion losses due to generating electricity, which is converted, stored, converted again and then used to drive the car. The more the engine can couple directly to the wheels, the more fuel is saved. Regeneration captures what would normally be lost to friction, therefore conversion to electricity is necessary. As we saw with the Fisker, the least-efficient way to burn fuel is to charge a battery, and then drive the car from that stored energy.

 

You are absolutely right. But I'd pay the extra $1000 to double my EV range. Lithium batteries are dropping in price, look at the Nissan LEAF as an example, its battery is going for $7k if you need to buy a new replacement. That's for a 24k battery. Our battery is much much smaller than that.

 

I'm not sure where you get the "near to 100%" figure. In a regular hybrid, (Plug-ins excluded) all the energy comes from gasoline. The energy gained from regeneration is just a portion of the energy being recovered, that would have been wasted.

Unless you started on a very large hill, and never planned to go back up there, the net energy used by the car has all come from gasoline.

 

And yet you said "the ICE doesn't do much battery charging" which is wrong and in direct conflict with what you just NOW said.
THAT is where the disagreement is.

 

That is called a Plugin Hybrid.

As has been discussed in several threads here already, having a bigger battery doesn't really gain you that much......if any.

 

It gains enough. I'd take a P.I.C. any day of the week. The difference on Fuelly seems to be around 15 mpgs for the PIP vs the Standard Prius. I can't link it as the PIP page isn't working right now on Fuelly, but I had looked at it a week ago and remember the differences.
But why would it have to be a Plugin? Our battery is so small that it wouldn't "need" to be, it would just be optimal.

 

BECAUSE.......as has been discussed on here several times in the past few months.......
ALL of the energy put INTO the battery and then subsequently used for propulsion really comes from burning gas in the ICE.
(OK not all but 99.5% maybe).

Once you accept that, it's easy to see why having a bigger (non-plugin) battery will not, by itself, gain you much of anything.

 

I think everyone would want more EV range, but there's always a price for that. The EV range you get from a non plug-in is really stealing from the "regeneration piggy-bank." The more you take out of it, the more you reduce the fuel economy in HV mode. Since all the mileage comes from burning fuel, using it in EV mode amounts basically to a less-efficient way to burn fuel.

With a plug-in, you are getting your EV miles from a different source, therefore fuel mileage is irrelevant to EV miles; it only
applies to HV miles.

A larger, lighter HV battery (such as lithium vs ni-cad) would be an advantage in situations where it would frequently reach levels of charge saturation or depletion. I'm not sure where such an application would lie, but I'm sure the Toyota engineers have studied it in detail. I'd be surprised if the current 1.3 kWh battery is inadequate to utilize regenerated energy in most driving situations, but I could be wrong. I welcome any informed opinion on this.

 

If that were the case my Prius would be constantly empty, since I rarely brake. The fact is: I've seen the battery gradually fill itself, even when driving a constant speed down the highway. That energy didn't come from the brake, because I wasn't using it. No instead it came from the engine. (The same is true with my Insight and Civic hybrids... they charge off the engine if the battery drops below half-full.)

Try this experiment: Drain the battery to near-empty with EV mode. Now go on the interstate & drive a steady 50 mph. You will see the battery gradually fill itself, even when no braking is happening.

 

That makes perfect sense when you drain the battery, but that's not the driving mode the Prius was designed for. Since all the energy comes from burning fuel, it makes sense to use in the most efficient way. The least efficient way to use that fuel is to drive around in EV mode, which suffers from efficiency losses due to conversion. A study paper I found recently estimates those losses anywhere between 30 and 70 percent.

The hybrid battery is designed to capture energy that would normally be lost in coasting, braking and idling. It only makes sense that the most efficient scenario would minimize the amount of energy going into the battery directly from the gasoline engine. The Fisker was designed without a direct coupling between the engine and the drive-train, therefore the numbers based on fuel-economy alone (excluding plug-in energy) were very poor.

 

Troy:
It's not worth it.
Trust me.

 

I'm still waiting for the "pulse and glide is the best so anything else you're doing is stupid" argument. And yet pulse and glide sheds light on where else a hybrid captures energy. P&G works because an engine is not efficient at a steady speed. Extra torque is lost. However, a hybrid can capture much of this extra torque. I understand that converting energy to the battery and taking it back out is not exactly efficient. However, if the energy captured would have been otherwise lost, then it's still a gain. That's why natural EV mode (i.e., not pushing the button to force it) is a good thing. It's cashing in on energy from braking, coasting, and extra torque that would have been lost in a standard car. And, yes, P&G may be more efficient but it's not normally practical.

 

He gets it.

 

Minimizing would miss out on opportunity. The information we keep providing shows that.

With both my ScanGauge and Torque app, I can clearly see that at times of low engine load, the battery-level going up... especially when the vehicle is not even moving.

My guess is not having access to that level of detail is contributing to these on-going misunderstandings.

 

Except more power and more range. But who wants that?

 

But what good is EV range in a non-plug-in?
And how does a bigger battery increase horsepower, exactly?

 

We are basically talking about just putting in a bigger battery, not engineering a whole new car.

You wouldn't get more "power" because the amount of instantaneous power drawn from the battery is "design limited", by the size of the motor and a built-in safety factor.

You wouldn't get more "range" because ALL of the energy consumed still comes from the gas in the tank.