Not enough stuff, even if you could get it to work. You would need a provision for battery sense (SOC), battery termperature, a cuttoff (and probably a current control or limiter) for the inverter and most likely a means to isolate the battery pack from the ECU sense lines. (I am not sure about the last one, but I do know that the ECU senses battery state prior to start.

Also, since you would be working directly with HV-DC, the voltage would require much more sophisticated control than the AC inputs from the MGs, which are controlled and conditioned by the ECU. I, for one, would not want to design a charging system that kept the ECU powered up, either.

RFB

 

Bob,

Good points - not necessarily deal killers, but certainly raising awareness of degree of difficulty, possibly enough to dissuade us from this approach.

Do you have a better idea ?

Do you think that a high voltage AC approach would be more workable ?

Do you think that a 12 to 14 v DC approach would work ? I think I read somewhere that the 12v to 300 v transformer in the part of the system that uses the high voltage to charge the 12 v battery was bi-directional.

How about an approach going in through the regenerative braking feature ?
Could we take a wheel off of the ground, spin it with an electric motor and let the car try to apply regenerative braking ?

Jack

 

No, DC is the way to do it. AC would require additional control components, rectifiers and sense circuits for the controls. I have already said that I think it would be a mistake to leave the ECU powered up to do this. so a separate control system would be required.

I had not heard this before. But even if it is bidirectional I suspect that the "reverse" direction trickle charge would lack sophistication in the controls necessary to shut down the charge when the batteries were at the deisgn SOC. Remember, that Toyota did not design the ECU to completely top these batteries in normal operation. As the batteries approach a topped SOC, the ECU begins to balance immediate use of traction power and traction assist to maintain some "wiggle room" in the battery state for braking and deceleration.

Will not work. First, you would probably need to take two wheels off of the ground. Next, if the traction system uses anything besides torque in its power transfer equations, you would need to fake it out. Even if you could get it to work, it would not be efficient. Remember that the charge from dynamic braking comes from the same drive train MGs, so doing this would require spinning the entire drive line.

Not really, the high voltage DC approach is probably correct if one wants to persue it. However, conversion of a parallel hybrid to a P-HEV involves more than just getting the battery to charge, and a lot of design issues come into play. First, there is the issue of power, a Camry that is limited to mild accelerations and 42 MPH or so on level terrain is a long way from a practical vehicle. The first hill, and for me in the morning, even getting up my driveway would require the ICE to start. With the battery topped, the start cannot drive the generator, so the efficiency gained from the charge is largely lost.

Next, the TCH is heavy enough that range becomes an issue. I can usually make about five miles on the traction motor under perfect conditions, on level roadway and without stops, over one portion of my morning commute. Any further distance, any hill of even minor significance, or any intermediate stop from intersection, school bus, construction zone or work truck is going to remove a significant portion of that invested charge.

No, I think a P-HEV has to be purpose built to derive any meaningful economy from its wall plug. It has to be more of a "no-compromise" vehicle with regard to weight, traction motor power reserves, battery design, etc. The Prius or Insight would be a better conversion, but even they would have slightly difference design characteristics as a pure P-HEV.

If you had ever driven an EV-1 (I did -- for six months ), you would understand these differences -- and the absolute need for them if an "electric" car is to be successful in modern urban environments.

RFB

 

Bob,

Thanks for the very quick reply and for taking the time to make such a full and well thought out reply.

Re. The complexities: You are convincing me that there is probably not an attractive way to do this, but "hope springs eternal."

Re. The range issue: My most frequent commute is well within the range of the TCH on battery power, but my trip home often drains the battery down to 2 bars, and that kills my EV opportunities for the next morning; so I would be delighted to find a solution that would let me simply add a few bars to the SOC overnight. More EV range than a few miles would probably be wasted on me.

For my longer city trips. I'm overjoyed with the 35 to 45 mpg I can usually get in gas/hybrid operation. I wouldn't need to do more EV mode on those. It's just those really short trips on which I need relief from the 25 mpg or less I typically get with heavy use of the ICE.

 

MG1 or MG2 put out 600 ac volts when coasting or if you use your brakes down to approximately 8 mph. The 600 ac volts goes through the Inverter under the hood. This converts the ac voltage down to 288 dc volts to charge the traction battery.

It works the same way to propel the car. The traction battery sends 288 dc volts to the inverter where its converted and stepped up to 600 ac volts then applied to mg1 or mg2, in some cases maybe both.

I understand that each traction battery has it's own small computer card that protects the battery. It also sends information though a bus line to the ECU reporting the battery temperature, level of charge, charge rate and etc.

No doubt they have chargers for the traction battery. The ones use them also add a extra set of batteries, matching the traction battery. The setup comes with a plug in charger. The cost is high though you get a healthy increase in mph.

For instance some Prius owners report that have had this conversion, have reached 100 + mpg. Although would take to long to recover the high cost. I would not like to carry the weight of the extra battery pack as the car weighs enough as is.

I would love to have a overnight plug in charger for the original traction battery. To be used the first few miles of driving in the EV mode till I get to the highway.

 

I've been imagining that most of the cost of these systems is in the cost of the extra battery.

I've also been wondering whether there's a way to purchase just the charging part of the system. I e-mailed one of the California sources re. this but got no reply.

Any Ideas ?

 

That may be their way of telling you no, it's a package deal. You might look around I think they are between 4 and 10 of these places. Two I read about long ago is in Denver and another in Austin, Texas.

Check out the Prius Forms they may list some locations.