Plug-in Prius...whats the point.?

Hi MicroAmps,

I am unfamiliar with units used down under, so forgive my use of US units.

The Prius' max EV speed is about 43 mph. The EV Prius speed limit does not have anything to due with maximum battery power output, but rather is a transmission limit to protect one of the electric motor/generators from spinning too fast. But Prius speed of course goes up to about 100 mph, which is where your analogy with grandpa's scooter goes awry.

At higher power output demands, nothing prevents you from using your battery's power; it is just supplemented by the ICE as needed, and less ICE is required this way.

The holy grail is more capacity. Higher battery power would be nice, but good enough as it is in the current Prius -- about 20 KW.

ICE: Internal Combustion Engine

 

Hi Microamps -

The point of a "plug-in" Prius is that the electric motor can augment the ICE at a wide range of speeds. It is just that under 35mph, the car is capable of running purely on electric power.

Even if you drive a lot of highway miles, the electric motor helps for acceleration. For city driving with a lot of stop-and-go and stretches under 50mph, having extra battery power can help even more. That is why people are experimenting with larger batteries in the Prius which can plug-in to recharge.

Today, I had to take several small trips at different times: To the bank, to the post office, to the store. (These trips couldve been linked with brain usage, but the brain wasn't working full-time today.) The majority of this time was spent on local streets at under 35mph.

A plug-in Prius would've worked great in my case, because little or no gasoline would have been consumed, and the batteries would be recharged off the grid when I got home at a cost considerably less than gas.

While these early experiments are very encouraging, batteries need to get cheaper and smaller (for the same power output) in order to become a really practical production item.

- Bob R.

 

Bob,

I find it useful to think of a PHEV just the opposite: The ICE can augment the batteries.

 

Basically, you're right; the usefulness is limited. I've heard folks say it's mainly useful for short-hop errand-running, where you don't want to use the ICE in its least efficient mode for, say, under 10 minutes, just to run down to the store.

 

You are basically under the impression that the electric motor is only used in EV mode, at city speeds. That isn't actually the case.

Just watch the Energy Monitor while cruising down the highway when the charge-level is in the green. You'll be quite surprised at just how much electric motor contributes. MPG is higher than usual during that time. Now just imagine what the effect would be with a much higher capacity battery-pack charged via a plug. Highway efficiency would be remarkably impressive.

 

considering the much higher conversion and efficiency ratings of line power, its much greater potential to generate cleaner power, and the ample opportunities to recharge, i think an extended range hybrid that only uses gasoline as a backup instead of the primary source of power is a no brainer and inevitable.

we have only lately realized that battery technology can be greatly improved and instead of yesterday's notions of not even trying for better EV vehicles because of limited range and weight/space issues, there is actually measurable progress on the road right now.

 

I guess my first post was unclear.

If you have X Kwh of battery capacity charged from the grid, it will displace petrol use for an equivalent energy amount.

Sometimes in EV only mode, sometimes in conjunction with the ICE.

 

we kinda have two threads going on nearly the same thing, so i will repeat. if we had a Prius that could go 20-30 miles on 100% EV power, even if it only worked at 40 mph or less, it would be a huge increase in performance.

our mileage is killed because of low speed driving. stops and starts kills us. hybrids only partially address those issues. even under the best of circumstances, we are lucky to be in EV mode 50% of the time. imagine if it was 100% for the first 20 miles every day. and all we needed to insure that range was 4-6 hours of plug time.

rumor has it that Toyota will intro a hybrid with Lith power in '08. give me an upgrade option of at least 20 miles EV and im in...

 

There are two considerations playing out here.

One is energy use, and where it is from
Two is ICE efficiency

If the comparison is between a Prius and a PHEV-Prius, both will have very efficient ICE use. Wayne Brown has added extra capacity to his Prius but does not plug it in as far as I know, and reports improved fuel economy. If he lives in a hilly area I can understand the improvement, but I think it fair to say that for most people the differences will be mild. In city driving, energy lost in braking will be the same. On the highway, energy used to overcome air resistance will be the same.

The real advantage is simply displacement of petrol by grid electricity. Pure EV or combined EV/ICE does not really matter. Worse case scenario with a driver who knows what they are doing: short bursts of ICE during accelerations (offset by 20 kW motor input) and 0.2 gallons gas/hour at speeds greater than 43 mph, up to speeds requiring less than 20 kW.

IT WOULD BE FANTASTIC

 

The car can, and will, run on electric-only up to 42mph. It normally doesn't, because it doesn't have that much battery capacity, and doesn't want to drain it. But if a plug-in conversion can persuade the system that it's got plenty of spare battery charge, and should be bleeding it off, then it will very much favour electric-running.

If you've ever reached 8 bars, then you will have seen that the car behaves quite differently - it will much more readily pull away from a stop without firing up the engine at all, simply because it wants to drain the battery. I'm assuming that a proper plug-in conversion would push the car towards its "8-bar" behaviour - attempting to drain the battery during travel - otherwise there wouldn't be much point; you'd end up at the end of a trip with a still full auxiliary battery!

And I don't know what your commute is like, but I certainly don't get above 30mph most days of the week.

 

That is exactly how the CalCars ECU is programmed.