Interesting ideas so far...

BTW Ford kinda did get their hybrid system from Toyota: "In a joint statement, the companies said that Ford Motor Co. will be licensed to use Toyota Motor Corp.'s hybrid technology in a system it is developing, which is already subject to more than 100 hybrid technology patents." From: http://4wheeldrive.about.com/b/a/072284.htm

Now as far as using EV mode.....

You can't assume 90% for each step of the process. Motors and generators can actually be more efficient. A pure series hybrid has no mechanical transmission. An engine runs a generator and pure electric power (with no storage) runs the wheels. This can evidently be more efficient than a straight mechanical connection.

The big loss with an electric hybrid comes in charging and discharging the battery. I've read somewhere that this process is around 25% efficient. With this in mind it is clear to me that SPL's idea has some merit, at least on paper. The key to the whole mess is where the energy comes from to charge the battery. If this energy would have been 100% wasted on braking anyway than it is more efficient to recapture at least some of that energy and use it to help propel the car.

Real world testing is a good idea but many variables will have an affect on MPG including temp and wind. Clearly a down wind leg is going to tend to have better mpg than an upwind leg. Warmer weather will yeild MUCH better mileage than cold.

Whoever said that the general method of getting HSD into EV is similar to the general method getting high mpg in general is also correct. It may not be the EV part of the equation that is responsible for higher mileage when driving with a light foot.

 

My understanding is Ford's independent development resulted in a system so similar to Toyota's that they had to pay patent royalties to Toyota.
Motors/generators are rarely more than 90% efficient and are usually operating below their peak efficiency, under 90% (cheap brushed DC motors are typically closer to 60% at peak!). A simple gearing can easily be well over 95% efficient.
NiMH cells typically charge/discharge with over 80% efficiency. That is, I can charge a flight pack for my RC plane with 1 amp-hour charge and get a 0.8 AH discharge from it. If I don't push the capacity (baby it like Toyota does), I get over 90% from the charge/discharge cycle. Lead acid, NiCad and LI technologies differ in efficiencies, but not that much.

Other than the Ford details, and these errors of scale, I agree with most of your points.

-- Alan

 

lakedude — I agree with most of what you say. However, if a direct mechanical transmission uses a CVT (or equivalent, allowing the ICE's rpm to be chosen independently of the car's speed), it MUST be more efficient than any series hybrid can be, since NO energy conversion takes place. The energy conversion process is where significant losses occur. The 90% conversion efficiency figure was a "ballpark" number that I used when I started this thread. In my recent posts (from after I conducted my experimental test runs) you'll see that I now believe that the TCH's mechanical-to-electrical-to-chemical-to-electrical-to-mechanical conversions must be significantly more efficient than I assumed. The reason is the very close correspondence between the FE figures for my "pure-EV" runs versus my "normal-driving" runs. I have always assumed that as much regenerative recovery as possible should be used when braking — as you say, there's no point in letting this energy go to waste. Since this energy ultimately came from the gasoline-powered ICE, one cannot throw it away with impunity.

Stan

 

Ok it sounds like we are all in the same ballpark here. Some of what I've said has been slightly misunderstood. The point I was making about the 90% number was that it was pretty close (close enough) on the motors and generators but the battery was much worse. Alan your RC example is flawed in several ways. You must look at the total power that goes into your charger not just the output "C" value. Also when you charge RC batts you are doing so at a fairly constant rate for a relatively long period of time. With a hybrid you only have a short time (during braking) to use regen to charge the batts. Some of that energy cannot be used because batts can only take so many "C"s. The rest of the energy is wasted making heat in dummy loads (guessing) or in the mechanical brakes.

BTW I'm an Electric RC pilot myself, what are you flying? I'm a GWS SlowStick man...

We sure got some big brained folks around here. Physicists and Engineers and the like....

Pure mechanic power paths lose energy to friction. Nothing is 100% BTW

From: http://en.wikipedia.org/wiki/Regenerative_braking

Can anybody find out where the extra energy goes for sure in a Prius? I have a hunch that Honda uses the rear defroster as a load because the back always melts ice/snow around the wires first, even when the rear defroster is off. It could be simple heat conduction. I guess I could go measure or read those fancy tech books I bought.......

 

I think most of the charging comes from the ICE and coasting, where the charge currents should be well within the capacities of the cells, but you are certainly right about the inability of the cells to get all of the braking generated current for anything more than very light braking with less than fully charged cells.

Most of my airplane NiMH cells can be charged comfortably at 4C (15 minutes from empty to full; faster charging makes for hot cells after charging). However, while 4C means 15 minutes (about 17 after inefficiencies!) on my flight packs, Toyota is only using about half the capacity of these cells, so a 4C charge rate would take these cells from 0 SOC to 100% SOC in about 8 minutes. There have been few times I've seen my SOC go from 0 to 100%, but I'm thinking it was about a 10 minute charging time.

As to my planes, my latest bird is a Blade CX2 helicopter. My hanger includes the GWS Slow Stick and Lady Bug, Clancy's Lazy Bee, Yard Bee and Baby Bee, EdgeRC's Mini Bird of Prey and Pocket Combat Wing, Mountain Model's Panic and Switchback (w/retracts), and a few of my own designs: deMeatray and Twisteron. (There are a few more already retired planes, too!!!) If you visit ezonemag, I am "fly".

-- Alan

 

The circuit diagrams show NO big power resistor to dump excess electrical energy that the NiMH battery can't take, either because it's "full" or because it can't take it at the needed rate. I believe that under these circumstances the TCH simply switches to normal friction braking. Since any car can brake much faster than it can accelerate, the electrical power flow during hard braking would be FAR greater than that during motor-boosted acceleration, and the current would be far too high for the NiMH battery to absorb, even if the motors and electronics could handle it. [That's why the audible "whine" from the motors during regenerative braking is much louder than it is during motor-boosted acceleration.]

Stan

 

I believe the inverter itself dumps the excess power. It has its own radiator (which is needed for all the switching it does just for managing the PSD with MG1 and MG2 even when the battery is not involved).
I expect that the engine is always idled down to the lowest possible RPM during braking, keeping MG1's speed as high as possible to maximize the efficiency of the inverter (minimizing the heating in the inverter whether charging the battery or dumping power). The increased MG1 speed relative to MG1's speed under power delivery might explain the whining.

I'm just speculating on both points.

-- Alan

 

alan_in_tempe — A separate water cooling system is used for cooling the MGs, the Boost Converter, and the Inverters. It is solely for dissipating the heat caused by the inevitable losses that occur in the transistor switches and in the motor-generators themselves. If there is no regenerative energy flow to the NiMH battery, there will also be no (well, negligible) heat losses. The regenerative braking is done solely by MG2. I see no change in the ICE's rpm when one applies pressure to the brake pedal to increase the regenerative braking beyond the low level that occurs during coasting. The whining noise that becomes audible when pressure is applied to the brake pedal is, I'm pretty sure, due to magnetostriction in MG2 and acoustic noise from the transistors, caused by the large current flows that then occur. These current flows can be much larger than those that occur during acceleration, because the rate at which the car's kinetic energy is being dumped into the battery during braking is greater than the rate at which energy is withdrawn from the battery during acceleration.

Stan

 

You may be entirely correct about everything else, except I am not sure about this last statement. The CVT (which is a function of the ICE vs MG1 speeds) is accomplished by letting MG1 and MG2 act in pairs with one generating and the other driving (or both generating or driving). No charging/discharging of the battery is necessary! Either MG1 or MG2 can be generating current. Both can handle about 50 HP generating or driving, while the max power out of the battery is about 40 HP. Hard slow speed starts will take current from the battery and MG1 (up to 50 HP combined) to drive MG2.

When more current is being generated than the battery can take (during braking), then I assume the inverter absorbs the excess.

I know MG1 & MG2 are inside the PSD and like the gears are bathed in the same tranny fluid which is cooled, but I did not realize that is on the same cooling circuit at the inverter. Does the TCH have three or four radiators (ICE, AC, PSD, inverter)?

-- Alan

 

The output from the electric motor is advertised as 105KW (~ 140HP) on the vehicle specs. Seems like overkill if the most it gets is 50HP of power.