Xringer's Prius C

[Xringer]

I'm not sure you could switch the ICE off & on, and do much better than the car's computer already does.

This 20 mile round trip was done in a very heavy traffic area, with hills.


You will notice that 62% (12.3 miles) of the trip was done in EV mode.
When the SOC is good, the car will stay in EV mode up to 45 MPH,
until the pack gets low or the hill gets steep etc.
The ICE only comes on when needed. It's so seamless, you can't tell
if it's running or not. You have to look at the power flow display.
I was surprised to see it run for 10 or 15 seconds and turn off.
It's amazing how fast the pack can recharge down hills or by ICE.
During that trip, the ICE may have been on & off 50+ times..

The EV range is short. Only about 1.25 miles.
But a slight downhill EV run can be much longer.
If you just want to move your car around a parking lot, without the ICE,
you just press the EV button when you turn the key to 'start'.
(Which turns on a 'Ready' display). If the SOC is ok, the ICE stays off.

Because of the way the battery is protected from getting a very low SOC,
it will last for many years. The car's computer program changes
the modes of operation very effectively.

The only EV hack I can think of is replacing the pack with a higher AH pack.
But, it's likely the control program would need to tweaked too.
I can't see that you would gain much, unless it was a plug-in.


My first hack idea was to add another 144v pack in parallel..
It might increase the EV range a bit.. Hard to say.
The rest of the system might be totally optimized to run with the pack..
BUT if it was charged from the grid. Maybe..

The plug-in idea might work if when you were coming home, you slowed
down under 45 for the last mile and hit the EV mode button..
When you got home, the pack would be in a lower SOC,
so a charge could be accepted via plug-in.
(Otherwise, the ICE will be doing all the charging).


Making the car lighter might increase it's EV range a bit. Take out the spare tire, tools & etc.?.


Some Prius Chat guys tow boats etc. But Toyota says not to tow at all.
Prius c Main Forum - PriusChat Forums
It will be hard to get warranty work done if you have been towing.

http://shop.tlcentral.com/store/pc/v...idproduct=1060

Not sure about the high speed MPG, but I read about one guy in Florida
who was running around at 85 MPH and complaining about 35 MPG.
You might be able to find out here: Prius c Fuel Economy - PriusChat Forums



The 'c' is the top dog of MPGs today. Only the EVs can beat it. (short range).
If you get a 'c', the most effective way to get the best MPGs is to learn to hypermile.

[Daox]

Originally Posted by RobertSmalls

Xringer,

I've got an eye on the Prius C. I'm impressed by its low price, light weight (2500lbs), small engine, and versatile hybrid system. The aerodynamics aren't as bad as most new cars, either. If I had one, I could probably press it into service towing 1000lbs, which means I wouldn't have to rent a truck when I want to move large things.

I'd like to know how much of my commute I could do on electricity with a Prius C. If you start with a full charge, how far can you get around town without engaging the gas engine? Rigging up a grid charger should be fairly easy, and developing an engine inhibitor should be possible.

I'm also interested in the fuel economy at extralegal speeds on the interstate. What kind of numbers does the Prius C generate at 75 mph?

RobertSmalls

I just went to the local hybrid group meet the other day. Wayne Mitchel (prius techie) did a presentation on the V and C. The C's range according to him is not even 1/2 mile (which makes sense because its pack is smaller than a liftback). The Prius' BMS won't allow you to drain the batteries under 45% and not above 80% (at least in a 2nd gen), so its not like you can really gain a whole lot by grid charging.

Highway is not where the C shines (not that its bad, just nowhere near your Insight). Wayne said that you're only getting about 60 mpg at 55 mph and it starts tanking once you get up to 65 mph. At 75 I wouldn't be surprised if you were down in the 40s. Its just not aerodynamic enough, and its geared higher than a liftback. In town you'll see much higher numbers as you can P&G very easily. Wayne achieved around 100 mpg in a small loop he does around the meeting site. He did the same loop in his 2010 liftback and got 85 mpg.

[Xringer]

I remember something about aerodynamic drag increasing with speed, not being linear.
Something like drag increasing at the square of the speed??

It's real easy to see in the (brick-like) Escape. On a flat road at 35-40 MPH, it gets 40+ MPG..
But on the highway it starts dropping off..

It's going to drop down to around 26 MPG at 60MPH and likely be less than 20 mpg at 70 MPH..

[RobertSmalls]

Thanks, Daox.

With a Cd of .29[1], I think it's safe to say the aerodynamics of the Prius C are just so-so. The light weight and efficient engine help make up for it, though.

I would expect modest gains from a grid charger, but it wouldn't require much effort, either. The C has a 144V NiMH pack, same as the Insight, which means I already have a charger for it.

If the 1KWh battery currently swings from 80% to 45%, that's .35KWh, which I reckon at 1mi without hypermiling. If you swing from 100% to 45%, it's about 1.5mi. :-/ Not great, but it's low-hanging fruit.

There's a part of me that sees a Prius C as a cheap platform on which to build a reliable plug-in hybrid NEV. I have a 9mi commute. A 10KWh lithium pack should do 20mi, weighs ~150lbs more than the current pack, and costs maybe $4000.

In order to match the road load of my Insight at 70mph, a Prius C with Insight tires would need a Cd of 0.20. That's not easy. Mod for mod, I don't expect the C to ever match the Insight. However, the Insight can't match the cargo capacity and EV potential of the C.

@Xringer: I proudly void warranties.

Originally Posted by Xringer

I remember something about aerodynamic drag increasing with speed, not being linear.
Something like drag increasing at the square of the speed?

F(drag)=1/2*CdA*rho*V².
So, yes, drag force is proportional to airspeed squared.

[Xringer]

Robert, what do you think of installing a second 144v pack in parallel with the existing pack?

[Daox]

Originally Posted by RobertSmalls

If the 1KWh battery currently swings from 80% to 45%, that's .35KWh, which I reckon at 1mi without hypermiling. If you swing from 100% to 45%, it's about 1.5mi. :-/ Not great, but it's low-hanging fruit.

If you charge above 80% the car will spin the engine using the electric motors to burn off the excess energy. You really only have 45% to 80% to work with unless you disable the Prius BMS.

There's a part of me that sees a Prius C as a cheap platform on which to build a reliable plug-in hybrid NEV. I have a 9mi commute. A 10KWh lithium pack should do 20mi, weighs ~150lbs more than the current pack, and costs maybe $4000.

Thats a great idea, and thats what I've done with my 2nd gen. The only drawback is the Prius C's limited EV speed. The Prius C's max EV speed is only 25 mph which isn't surprising since its geared higher than the liftback. The 2nd gen Prius has a max EV speed of 34 mph. I'm not sure about the 3rd gen, but I think its quite similar to the 2nd gen.

I think your best bet is going with a 2nd gen. You can get them for under $10k now and besides weighing 400 lbs more than a Prius C they have more benefits IMO (aero, space, used parts).


Installing a 2nd pack in parallel with the original pack has been done and is one of the few techniques (and probably one of the more effective) in making a PHEV Prius.

[Xringer]

"The Prius C's max EV speed is only 25 mph "

There must be something wrong with mine, since I was going up a slight hill at 40 MPH, in EV mode the other day..

I read the transition point to EV occurs when you drop down under 46 MPH.
CleanMPG Forums - View Single Post - Is there going to be a section for the new Prius C ?

I'm not sure, but I think I've been in EV mode going down hill at around 50 MPH..

"WS" is explained here.
http://techno-fandom.org/~hobbit/cars/warpstealth.html

[vskid3]

If my understanding of the Prius' powertrain is correct, EV mode should be physically possible up to the top speed, provided the motor can produce enough power to move the vehicle at that speed. The main motor is always spinning when the car is moving, whether the gas engine is on or not. I assume that the cutoff speeds are the point where the motor either can't move the vehicle on its own (in most circumstances) or that it uses too much power to have any kind of range. With a decent size battery and a controller that would allow it, I think the Prius could function as a 100% EV at any speed possible with the gas engine (as long motor can put out enough power to overcome the drag).

[Xringer]

http://techno-fandom.org/~hobbit/cars/hp-color.gif

Sweet spot refinement

Seems like the HP needed at lower speeds can be obtained from the pack.
Too bad the pack isn't a bit larger.

[Daox]

By EV mode I mean the mode you enter by pressing the "EV mode" button. You can drive on electric only in 'hybrid mode' after the engine has warmed up, but you can't use the electric motor nearly as agressively as you can in EV mode. You can travel at freeway speeds in EV mode, but not only does the electric motor have to provide power to move the car, it also is going to be providing power to spin the engine which is horribly inefficient. At least in the 2nd generation Prius, once you hit the 41 mph limit, if the engine isn't spinning one of the two electric motors is spinning around 10k rpm. To stop it from grenading (aka to slow it down), the engine must be spun.