Software that controls Prius

You're way off base. The primary criteria for the Prius is to reduce emissions, and to do so it needs heat for the catalytic converter. That's why the engine comes on early and stays on until the system is heated. As for use of the electrical system, the more the car runs on electricity the worse the overall mileage. Ideally you want the car to only run on the engine at the most efficient speed, but of course it's impossible to do that in the real world, so it does the best it can. It's a common rookie mistake to think that electric driving equals good mileage, but it doesn't work that way. All that electrical power comes from burning gas in the engine, and it's more efficient to not convert it to electricity to convert to chemical energy in the battery just to convert back to electricity to convert back to mechanical energy. If that last sentence seems a bit long and complicated, you are starting to get the point.

Tom

 

Well, there's quite a bit of things you got there. I've got answers to only a few.

1) the battery meter on the Prius does not represent 0% state of charge (SOC) at 1 bar, and 100% SOC at full bar. it really actually represents 40% - 80% or 100% i forgot. The reason being, batteries dont' last very long when it's being constantly discharged fully and recharged, that's why Toyota can warranty the battery up to 100,000 miles because the car never goes below 40% SOC.

2) The battery capacity IS SMALL. The hybrid was never designed to be driven on electric alone. How it works is, it'll push the car off the line with the electric engine because that's when the car needs the most torque to get going, and using ONLY gasoline engine is where it wastes the most gas. So they'll use electricity to start the momentum, then kick in the gas engine. so essentially the gas engine is only there to cruise the car, thus not much gas wasted.

3) Keep in mind, the battery gets charged through the gasoline engine and some from regenerative braking, so there's a fine balance between how much you use on the electric before you're going too far and have to spend too long of a time to waste gas and charge up the battery. So the way the Prius is designed is already optimized at the Toyota factory.

4) the battery is quite a sensitive thing, it likes the temperature that you like. When just powering up the car after sitting a while, if the engine is cold, it'll first try to warm up the engine. IF the battery is too hot because the sun is beating on the interior, then it'll also not use the battery too much. Same if the battery is too cold..

5) lastly, the battery technology is still FARRRR below the demand that current high tech things needs. We really need to have a break through on portable power but until then... we're all restricted on the battery. It is proven that using electricity is much cheaper than using gasoline.. but.. there are no battery technology that can make that practical just yet. Lithium Ion sure is better, but its much more dangerous in heat.

Sorry for the long post, but that's as far as my understanding is, if anyone has anything to add, or correct please do so

 

Sit. A: Turn off the A/C, it's a big drain and causes the ICE to run more frequently. When you first turn the engine on, the catalytic converter needs to warm up in order to function properly, so the ICE will run for a minute or two.

Sit. B: When driving using battery only, the battery drains pretty quickly. The ICE will turn on to recharge, and it only takes a half mile or less to run the battery charge level down, faster if you're running the A/C and/or other electrical equipment.

Also: The battery rarely is allowed to get to lees than 1/2 capacity to avoid possible damage or premature battery failure.

 

Maybe. Maybe not.

I'm sure Toyota engineers ran the numbers years ago and settled on what we have now in the Gen II. We'll see how the numbers have changed when we get more details on the 2010 model.

I'm interested in adding battery capacity to my new 2008 in future, when the tech gets better, cheaper, safer, smaller, lighter, longer lasting etc. But for now I'll be happier keeping her stock.

 

Hiremichaelreid,

Okay, what car is your avatar?
If I had to guess, I'd say Dodge.....(darn it, my bother-in-law has a white one and I can't remember the name of it)
He doesn't drive it, it sounds like the engine hasn't had oil to the lifters in years.

ZC1

 

The Prius is not designed to maximize electric use or maximize fuel economy. It was designed to minimize emissions to be a sustainable auto for the future. Good FE is just part of that solution.

The HV battery in the Prius is used as a buffer to store energy that would otherwise be wasted during braking or when the internal combustion engine (aka ICE) is not running efficiently. But there are conversion losses when the energy is used to charge the battery and losses again when the battery energy is used to propel the car down the road. That is why Tom (qbee42) made the statement that purposely trying to force the car into electric mode will result in lower mileage.

A larger battery would allow longer runs in EV mode and would allow you to charge the battery from your house (external source) to get better mileage. This is the idea behind the PHEV (plug in hybrid). People are modifying cars for this now; it should be commercially viable in a few years.

 

As everybody are saying, Prius is a gasoline/electric hybrid vehicle and all energy are came from gasoline. A famous Pule&Glide technique is to avoid using battery power.

The Prius history is 40 modules of battery (NHW-10) -> 38 modules (NHW-11) -> 28 modules (NHW-20), however the vehicle performance and fuel economy number became better and better. That's the innovation.

Ken@Japan

 

It's not a matter of agreeing or disagreeing. qbee is correct.

All of the potential energy in the car came from gasoline (whether that PE is stored in actual gasoline, in battery charge or in height above sea level). Losses due to inefficiency are incurred whenever you transfer PE to kinetic energy or KE to PE. If you try to use battery power alone, you're relying on potential energy that was inefficiently generated and stored.

All-electric cars and Plug-in Hybrid Electric Vehicles are very fuel efficient because they derive their battery power from the city's electrical grid, and thus don't necessarily require the burning of gasoline to charge the battery. If you had a PHEV you'd want to drive on battery power as much as possible because you might be able to completely avoid using gasoline. The Gen II Prius is not a PHEV, and should be driven like any other car on the road (with some Pulse and Glide thrown in if you want).

On the general point that "the computer is doing the wrong thing", that's incorrect as well. The Prius control laws are designed with the following goals in mind (in order of importance):

-Prevent damage to the car
-Maintain battery life
-Reduce emissions
-Increase fuel economy

The computer does an extraordinarily good job at all of these, but its priorities are set. You'd get better fuel economy if the engine didn't run after starting the car to warm up the cat, but then the "Reduce emissions" requirement would not be met. Since the car follows the heirarchy above, emissions control beats fuel economy.

Also note that increasing the storage capacity of the battery without changing the manner in which it is charged will not make an appreciable change to your fuel economy. The conversion losses would still be the same, but you'd just have a bigger bank to throw energy into. This would of course allow you to run longer on all-battery, but as we've learned this isn't a good thing to do.
The one reason why a larger battery would be beneficial is if you routinely drive down long, steep hills. A larger battery would be able to capture more of the energy from descending the hill before the car would have to change over to engine braking to waste energy.

 

1994 Dodge Stealth TwinTurbo AWD/AWS w/ 320 HP and 17 US MPG

Back end is shown because it's waving goodbye. I sold it last night and deliver it Thurs. AM, and get my new Prius Thurs. PM. lane:

Yeah, the hydraulic lifter-tick issue. Takes a few minutes and/or a few revs after startup and it's gone on mine. Always been that way. Minor annoyance for the car.


IMO, the Stealth was a "showcase of engineering" , while the Prius is a "masterpiece of engineering". Of course they were both engineered for somewhat different requirements...

 

Zack,

You didnt come here just to troll did you?

 

The operational model you describe, and expect, will be used in the Chevy Volt.

In short, batteries are difficult and expensive. The battery in a Prius is used as a load leveler, not as the primary energy storage. The battery allows the engine to operate in a restricted range in which it is clean and relatively efficient. Everything else about the Prius follows from that.

The Prius engine always runs for a minute or so after first starting the car to warm itself and the catalytic converter up to operating temperature ASAP.

 

Good summary, was about to write more or less the same thing I would just add that increasing the battery capacity has even been tried and shown to accomplish very little. One of the early pre-PHEV hacks was to try adding a second HV pack in parallel with the first. Several folks eventually got this working and found that it did not really help FE much at all. To reduce gas usage you need to charge from a source other than the ICE, IE offset gasoline with coal/wind/solar/hydro/nuclear/natural gas etc. Then a bigger battery helps a lot, as the more you can store the more gas you can offset at one time. Its not necessarily much more efficient, but can be much cleaner depending on where the energy comes from.

Rob