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It's all relative I reckon, the Prius started being manufactured 7 years ago, with the belief that more mass production will help drop the price.

7 years later, there's not much difference. Where will we be in 7 years time from now ? :?
 

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I haven't seen the reason WHY they should get cheaper. The "explanation" that they will be smaller isn't enough. Smaller isn't necessarily cheaper. But then again, maybe they didn't want to reveal how they will cut costs to competitors.
 

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Smaller might be an indication it may become more integrated. Maybe this says they'll try and get the inverter more integrated with the battery pack. And of course if they go LiIon the battery pack will get smaller too. Or else the inverter may get smaller if the battery pack gets more voltage (typical of LiIon) and of course there's are ways to make the motors smaller.
 

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I never understood why they upped the voltage at the inverter, rather than at the battery pack. I understand higher voltage means lower current for the same wattage, and thus has less loss over parasitic resistance, but since they dropped the voltage going through the transmission line from the battery to the inverter, there's more potential loss there.
 

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I guess to keep the battery costs down. They cut the pack back from 38 modules (274 volts) in the '03 Prius to 28 modules (201 volts) for the 2004 Prius, and I reckon a lot of this was to cut costs (and a little bit of weight). Maybe the money saved from the lost 10 modules more than makes up for the cost of putting in the 500V DC converter? :?
 

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DanMan32 said:
I never understood why they upped the voltage at the inverter, rather than at the battery pack. I understand higher voltage means lower current for the same wattage, and thus has less loss over parasitic resistance, but since they dropped the voltage going through the transmission line from the battery to the inverter, there's more potential loss there.
Efficiency zoomed to almost 99% with higher voltage rather than higher current. This is typical for all inverters not necessarily just Toy's. This is one of the main drivers behind the (eventual) switch to 42V for "normal" cars. And with their move to the newer FET technology within the inverters they were able to make it smaller and cool it better. Design is also easier for the batteries when they limit the DoC to between 40 and 80%. The battery cell rarely changes from the 1.2V. Now with LiIon battery cells at 3V who knows what will happen. They might actually see a 500 to 600V battery which means the inverter will shrink. Right now the Toy engineers are probably trying to pin down the range of DoC curves they might actually see and, of course, what range is more reliable. THS III may be an eye opener.
 

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DoC?

Anyway, the issue I am pointing out is the resistance of the lengthy cable going from the battery to the inverter. The voltage was lowered for that, which means the current has to go up for the same power demand. That means more loss over that cable for the same wattage demand.
 

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DanMan32 said:
DoC?

Anyway, the issue I am pointing out is the resistance of the lengthy cable going from the battery to the inverter. The voltage was lowered for that, which means the current has to go up for the same power demand. That means more loss over that cable for the same wattage demand.
I totally agree. You'd think they'd have stuck the inverter closer to the battery pack to prevent such a loss including some rather lengthy calculations involved with the amount of loss that chages with the weather. But the inverter need a little more active cooling than the battery and they can share the cooling in the engine area. And as you know the engine compartment is not an ideal place for the battery as well as being a safety issue.
 

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DanMan32 said:
I never understood why they upped the voltage at the inverter, rather than at the battery pack. I understand higher voltage means lower current for the same wattage, and thus has less loss over parasitic resistance, but since they dropped the voltage going through the transmission line from the battery to the inverter, there's more potential loss there.
Maybe where the real work is done.. deep inside.. there are many tiny windings etc that can really take advantage of the lower amps... getting the power there is maybe just a simple hookup that is not so sensitive on the size of wire or circuitry they need to use.
 

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windstrings said:
DanMan32 said:
I never understood why they upped the voltage at the inverter, rather than at the battery pack. I understand higher voltage means lower current for the same wattage, and thus has less loss over parasitic resistance, but since they dropped the voltage going through the transmission line from the battery to the inverter, there's more potential loss there.
Maybe where the real work is done.. deep inside.. there are many tiny windings etc that can really take advantage of the lower amps... getting the power there is maybe just a simple hookup that is not so sensitive on the size of wire or circuitry they need to use.
Say what?

By the way, I didn't mean the whole inverter, but just the booster. However that would mean that the airconditioner compressor would have to operate at 500V also, though that wouldn't be necessarily a bad thing.
 

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Hi All,

A little technical note. I am no expert in motor control, but the length of the wires from the inverter to the motor needs to be kept at a minimun to minize high frequency reactive fields, and the really bad effect of those fields - cross coupling into control inputs (let alone the radio reciever) ! EMC/EMI (as its called) can wreak havoc with microprossors themselves , and the low-level signals used to sense the status of the system. Harmonics of the inverter signals probably easily extend into the AM broadcast spectrum, and possibly even the FM broadcast spectrum. The shorter the distance between the inverter and the motor, the smaller the volume one has to protect from the varying electromagnet fields. This is probably why the inverter is right on top of the MG1/2 housing. Let alone its a good place for cooling lines and cooling air.

A professor I had (the one who was building the Chevy Vega Hybrid car for GM in the 70's), had worked on the motor controls for tanks. He said one problem they had was the turret would oscillate! Until they cut all the lacing of the wiring harnesses, and spread the wires apart. Apparently the position sensor signal wires were picking up coupling from the turret motor amplifier wires.

From the battery to the inverter the electricty is highly filtered by the capacitance of the battery and probably another cap in the inverter itself. So, there is not allot of varying high frequency fields around those wires.

Additionally, I believe minimizing motor and wiring inductance (between the inverter and motor) is important to get quick response time. This limits how high the motor voltage can practically go.
 

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One of the extra-batteries crowd observed that the HV battery
leads have many fine strands, which tends to increase current-
carrying ability and reduce voltage drop. I think he
found that the length of these cables didn't
really present any appreciable resistance, or not
enough to worry about at 100A max.
.
_H*
 

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Hi Hobbit,


Finer and finer wires do not increase current carrying ability of a conductor. Its the total conductor cross section area (at low frequencies) that results in the current carrying capacity.

The fine wire has mechanical advantages. The finer each conductor in a composite conductor, the less force it takes to bend, the smaller the bending radius can be, and the more flexes it can take over a given mandrel radius before any one of the fine wires breaks. The more of the fine wires that break, the less the current carrying capabilty, and the hotter the wire runs, which tends to cause more wires to break with flexing. Heavier stranding of the wire is less reliable, as a break in any conductor results in a higher fraction of loss current carrying capacity. The thicker any individual strand, the more likely it will break bent around the same mandrel.

Robots tend to use the very fine wires as they are flexing the cables hundreds of times an hour, 24 hours a day, 365 days a year. And it can be a problem with randomized failures in complex multi-robotic systems. Welding wire is usually finely stranded soas to be flexible enough for a human operator to bend into the needed position, yet have high enough current carrying capacity for welding. Car customizors have commonly used welding wire to relocate batteries into the rear or cars for better vehicle balance, as it can be formed into the needed shape to route through the car body. Most likely this is the reason for its use in the Prius.
 
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