What is the usable power in KWh ?

What is the usable power "energy" in KWh ?

I am am trying to find out what is the usable capacity in KWh of the NON PiP Prius ??? I am trying to asses if any conversion kit makes sense...

In my manual page 551 says.

Capacity 6.5Ahr (3HR)

28 modules

201.6V

I am little confused (although I am an EE) so what is the actual usable capacity, and how this can be calculated from these numbers...

Capacity can not be by modules that doesn't make sense.

So in theory, Overall capacity x Voltage would give Power something 1.2KWh ... (guess max)

But how does this relate to the fact the system only uses a very limited SOC range?

So my question is this btw the "discharged" state like 2 bars (never ever seen 1) and the all bars (only see it maybe 2-3 time over almost 3 years) mostly the last bar is empty ... how much power/energy can be stored???

This power comes from regen breaking and extra ICE power. That is the main source of "saving". More energy could be stored instead of wasted better the saving will be , right?

I am sure someone can tell

I am trying to contrast this to a 4KWh conversion kit which claims 4KWh energy can be used from the unit (full capacity is higher ... same reason they do not use the full range... to keep the cells live longer...). And also claim that regen can store "energy" back there. So even if I can not charge at work or longer then the EV could go I would potentially save with a bigger KERS.

And if anyone knows how this compare to PiP would be awsome !!! (maybe my next prious)

Your calculation is correct. But, the 6.5Ah figure is the total capacity of the cells. Mind you, prius limits the usable capacity to only one third of that to maximize battery life. There is a trade-off between depth of discharge and total life cycles in every type of battery.

OK so what you are saying, we can say that about 400Wh or perhaps a more familiar term 0.4KWh (this is the unit on our electric bill)

So a 4KWh phev kit would (even without always charging) would give a 10 times bigger buffer... This will be very usefull in some up and down driving (and stop and go too).

Let see what anyone else thinks...

KWh is a unit of energy, not power. Which do you want: power or energy?

Tom

Regen back into a PHEV add-on pack is very much a second-order efficiency gain, and possibly even would result in reduced MPG if you never plug it in. Once your PHEV pack is depleted, then charging it via regen means that you are charging it with the ICE. You want a plug to charge your PHEV pack, not the ICE. Let regen go into the smaller traction battery instead. Plan on charging the kit as often as possible, and plan on having lower MPG than you do now if you don't plug it in. The added weight will offset the increase in regen capture efficiency due to slightly more favorable Peukert's constant.

These systems work best with you use the ICE for acceleration and hills, then try to cover ground with the ICE off on flat and downhill.

Sorry .... I was a little loose on the terms.

I meant re-usable energy stored ... (what power actually the traction battery have not even documented).

If I am correct it would be: what amount of energy it can pump back to the motors (in watts) per second ...

But anyway ... yes both are important ...

OOOOOPS I should have asked the question little better... thanks

I do not have a complete understanding for this ..

But just for argument sake, I do have occasionally when the current track.. battery IS full and I KNOW the regen goes to heat ... if that would go to the PHEV battery (which have 10x the capacity to store it) that would sure to help ...

Same goes to excess ICE (often the ICE will be on for other reason and excess energy can go nowhere .. like highway ....)

Am I wrong ???

I can not see how this can hurt MPG ... the scenario is that yes at home I can plug the PHEV in ... but not anywhere else (even if the PHEV kit battery is depleted)...

No-plug Prius has 1.31 kWh and it uses only 40% of it. Usable is 0.524 kWh.

Could you enlighten me (and others) from where this is coming from ... Of course not doubting at all you are right.

It seems very close to what I just "assumed" from the manual and other publicly available info ...

But thanks this is useful .....

in watts, not watts/second. watts/second does not have a meaning for the kind of questions you are asking.

Lets say you are pushing a big rock. Are you interested in how fast you can push the rock, or how far ?

201.6V x 6.5Ah = 1.31 kWh

HV Battery full 8 green bars is ~80% SOC and one purple bar is ~40% SOC. Prius maintains that range to prolong the battery life.

It's a common mistake. This is the brief explanation:

Force is how hard you push on something. Generally this is expressed in units of pounds or newtons.

Work is when you exert force over a distance, such as skidding a box over the floor. Work is a form of energy, so it is usually expressed in units of joules or calories.

Power is how hard you work, or work per unit time. It is usually expressed in units of watts or horsepower.

Power is no indication of the amount of work. Something can be very powerful, but only for a brief instant, and therefor do little work. Or it can work slowly but continuously, producing a lot of work but not much power.

So when you talk about putting energy back into the battery you want units of work or energy, not power.

Much of the confusion comes from the electrical distribution industry, who insists on measuring electrical energy in compound units. They like to use watt-hours, which is power times time, which equals energy. It's a round-about way of doing it, and causes no end of confusion to non-engineers.

Tom

Well I DO understand that and I or WE should be concerned by both ...

So I am interested not only the "capacity" energy of a PHEV kit but also the power. Like how much juice it can pump back, or how fast I can push rock, which actually translate to the max speed in EV....

Both are VERY important numbers for consideration of a PHEV kit...

Let me attempt to correct your misconceptions.

The added weight to include that 10x capacity, that you have to lift over the hills, as well as expend energy to bring up to speed, will cause lower MPG. Can you at least acknowledge that fact?

So, after paying a weight penalty in your efficiency, you can perhaps capture slightly more energy. But you need to be coming down a seriously long mountain grade for it to make any difference. And if you are coming down from the top of Pike's Peak, for example, you would have expended more energy than you could capture by lifting the weight of the pack to the top.

"Occasionally full" means that there is not a lot of energy going to waste. And I can't see you losing out on much if any energy from regen, living in Oceanside, NY. For comparison, I have a 54 MPG tank going right now in my Gen II, which is less efficient than your Gen III, and I live in the Rockies, and I see 80% SOC daily.

If you are on the highway, there is a constant dance between battery charging and discharging. When you accelerate or go up even the slightest incline, the battery will discharge. When you slow down, the battery will charge. Otherwise, the HV computer attempts to manage state of charge (SOC) to maintain 60%. On the highway, there is generally not enough power from the battery system to overcome wind resistance, and so the ICE must be used. There is no excess energy that is lost on the highway, other than a second order effect like the ICE operating at an output level that is less optimal. But how do you tell the ICE to operate at a higher output, most optimal level, simply because you have a PHEV kit?

The PHEV will help you on the highway by keeping SOC above 60%. Then the HV computer will preferentially use battery power and keep the ICE at lower power output. That's called blending, and that can get you fairly high MPG.

Yes

Think about the Plug-in Prius drivers. They get 13 miles of EV range per charge. That's about 1/4 gallon of gas saved. If they plug in once per day, six days a week, the most gas that they will save is 78 gallons per year. If you decide to PHEV, think about your driving pattern and see if it would be possible to plug in two or even 3 times per day. That's the only way it even begins to come close to being worthwhile.

Also, the remarks of PiP drivers that don't charge (i.e. a long trip) is that they generally get 50 - 60 MPG. These are generally very experienced Prius/hybrid drivers already in a car with a brand-new pack. They can't get 70-80 MPG simply because the battery pack is larger and can capture more regen. Your non-plugging-in results could be worse than theirs, because your car is not optimized for regen with a large add-on pack.

I think from the start this thread has missed the point. The Prius IS NOT an electric vehicle! The fact you -can- be propelled by electric only is just "window dressing". The hybrid electric part is there so the Atkinson cycle engine is usable, it's not there to drive the vehicle down the road.

Remember, if you were to use electric only you would be severely limited in how much power you could use. The fact the battery -contains- a certain amount of energy doesn't mean you can actually -use- that energy. You are limited in several ways on how much energy you can use and how fast you can use it. First, current you can draw is limited to protect the battery. Then you are limited in how much current over time (usually the limit is time) you can use, as the battery heats up and that will shut you down. Next, the system will only let you run the battery from about 80% to about 30% of the 6.5 A-Hrs. Finally, the electric motor is only so powerful (around 40 HP) so that will limit you. I -suspect- you would eventually overheat that as well if you had enough battery power that you could use, but currently it's the battery that is the limiting element. And that's because it was -never- intended to propel the car on its own.

Well that is not really true anymore a 4KWh unit is less then 100lb now. which equals to a small (very small)person ... My dog weighs more than that. I may even have that much "stuff" in the car sometime, if I count the extra wheel pump emergency bottled water, blankets etc.

I am not talking about full 10KWh kit ...

So this is not really a big issue...

I am not convinced by this. I am watching RPM and I KNOW that battery will go down to two bar on "highway". Not talking about 65MPH constant drive just about 50MPH on parkway which I 'mistakenly' call highway

And the battery goes full if I really pushing the ICE again and have some breaking ... along the way (that is how my wife drives anyway, and she always "proud" she has the battery full ....

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This last point is what I was getting at mostly with my driving pattern (lots of breaks) and less chances for just simply glide around ... and "carefully" accelerate at my leisure

I could almost get to work with only elctric with a 20 miles range kit ... so 1/3 of a gallon daily (soon many parking place will allow charging and a normal workday WILL be enough to re-charge)....

so I could potentially save 2/3 gallon with current gas/electric prices that would mean about $2.5 saving a day.... and yes this may not ever pay back (2000 days would be the $5000 what it cost to convert) quick calculation is 8.5 year commuting...

So I agree this would not worth the money (even in optimal conditions).... case closed.

But this is why I asked. What the current GenIII usable energy capacity was? .....

Just a bit of additional information:

1. The actual Prius HV battery voltage varies with SOC so the available energy is a bit higher than the nominal calculation stated earlier in this thread.
   1. About 200v at 40% SOC (low end of usable energy)
   2. About 220v at 80% SOC (high end of usable energy)
2. The modules in Gen3 Prii have a lower series resistance than those in the Gen2 Prii so the power (watts) available is higher in a Gen3.
   1. Gen2: 100A max current rating
   2. Gen3: 130A max current rating

JeffD

Nope. Neither of those is in fact a loss of energy to the car system, one is a conversion to potential energy the other a conversion to kinetic energy. Both can be recovered, or used as a substitute for chemical energy later. Energy losses (to the system) are brakes and air resistance.

I've wondered about this. It seems like you have more get up and go (pardon the layman's way of thinking about this) using the battery when the battery is fuller. I presume this explains it.

You also have a larger, more powerful engine in the Gen3.

JeffD