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Thread: Power Meter

  1. #1
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    Power Meter

    Can anyone explain exactly what the power meter measures? That's the big one on the left - not the battery power level on the right.

    The meter goes up to 150 kW and I've read that the total output of the gas/electric motors together is 148 kW. I assume that the meter shows what the combined output is for the system and not just the electric side - correct? The part that gets vague for me is when the meter dips into the blue zone that means the battery pack is charging during braking. Why doesn't the meter show charging when sitting at idle with the engine running such as when first starting in the morning? Is that because there's a net lose when charging the battery from the gas engine? Maybe there's only a positive gain in power during braking - which actually shows up as negative on the meter - in the blue zone below the zero point. Did I just answer my own question?

    Nissan says very little about this in the manual and after my cunfusing ramlblings above, I can see why.

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  3. #2
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    Quote Originally Posted by lloyd123 View Post
    Can anyone explain exactly what the power meter measures? That's the big one on the left - not the battery power level on the right.

    The meter goes up to 150 kW and I've read that the total output of the gas/electric motors together is 148 kW. I assume that the meter shows what the combined output is for the system and not just the electric side - correct? The part that gets vague for me is when the meter dips into the blue zone that means the battery pack is charging during braking. Why doesn't the meter show charging when sitting at idle with the engine running such as when first starting in the morning? Is that because there's a net lose when charging the battery from the gas engine? Maybe there's only a positive gain in power during braking - which actually shows up as negative on the meter - in the blue zone below the zero point. Did I just answer my own question?

    Nissan says very little about this in the manual and after my cunfusing ramlblings above, I can see why.
    i can't say for sure, but i was under the impression the meter is how much power is going to your transmission. it is definitely both the gas and electric power output.

    blue is when it is charging. when you're warming up, the car doesn't charge the battery (my guess to this is because when warming up, you want the engine to move freely and not put a load so quickly on it).

    when charging the battery from the gas engine, if you agree with me that that is the power meter of the transmission, there technically wouldn't be power going to the the transmission and direct connection between the engine and motor.

    i think my thinking makes sense

  4. #3
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    I think I finally figured out how this whole things works. The NAH is actually a full time electric car - similar to a diesel electric train. The transaxle has both a generator and a traction motor. The traction motor, which drives the transmission, can only be powered by electricity. The electricity comes from either the generator driven by the gas motor, the battery or a combination of both. Your explanation that the power meter measures what's going to or coming from the transmission - actually the traction motor - is correct.

    Edit - correction!

    Doing some more research I discovered there are series systems and parallel systems. What I described above is a series system but have now learned that the Toyota system, which is what the NAH is based on, is parallel. That means that the transmission can be driven by both the motor mechanically and the traction motor electrically - either at the same time or each one alone. There some "planetary gears" that allow this to happen.

    Kind of back to my old question now about the power meter and how the gas engine figures in the mix.

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    OK - this is getting too deep for me.

    I was looking at Wikipedia and discovered this:

    "Series hybrids use an internal combustion engine (ICE) to turn a generator, which in turn supplies current to an electric motor, which then rotates the vehicle’s drive wheels. A battery or capacitor pack, or a combination of the two, can be used as a buffer of sorts to store excess charge. Examples of series hybrids include Renault's Kangoo Elect'Road, Toyota's Japan-only Coaster light-duty passenger bus, DaimlerChrysler’s hybrid Orion bus (earlier post), the Chevrolet Volt concept vehicle, and many diesel-electric locomotives. With an appropriate balance of components this type can operate over a substantial distance with its full range of power without engaging the ICE. As is the case for other architectures, series hybrids can operate without plugging in as long as there is liquid fuel in the tank.

    Parallel hybrids, such as Honda’s Insight, Civic, and Accord hybrids, can simultaneously transmit power to their drive wheels from two distinct sources—for example, an internal-combustion engine and a battery-powered electric drive. Although most parallel hybrids incorporate an electric motor between the vehicle's engine and transmission, a parallel hybrid can also use its engine to drive one of the vehicle's axles, while its electric motor drives the other axle. The Audi Duo Plug-in hybrid is an example of this type of parallel hybrid architecture. Parallel hybids can be programmed to use the electric motor to substitute for the ICE at lower power demands and to substantially increase the power available to a smaller ICE than would normally be used, either mode substantially increasing fuel economy compared to a simple ICE vehicle.

    Series-parallel hybrids have the flexibility to operate in either series or parallel mode. Hybrid powertrains currently used by Ford, Lexus, Nissan, and Toyota, which some refer to as “series-parallel with power-split,” can operate in both series and parallel mode at the same time. At present, most plug-in hybrid conversions of conventional hybrids untilize this architecture."

    Sorry I started this whole thing.

  6. #5
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    Don't be good info.

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    Power meter confusion

    Quote Originally Posted by lloyd123 View Post
    Can anyone explain exactly what the power meter measures? That's the big one on the left - not the battery power level on the right.

    The meter goes up to 150 kW and I've read that the total output of the gas/electric motors together is 148 kW. I assume that the meter shows what the combined output is for the system and not just the electric side - correct? The part that gets vague for me is when the meter dips into the blue zone that means the battery pack is charging during braking. Why doesn't the meter show charging when sitting at idle with the engine running such as when first starting in the morning? Is that because there's a net lose when charging the battery from the gas engine? Maybe there's only a positive gain in power during braking - which actually shows up as negative on the meter - in the blue zone below the zero point. Did I just answer my own question?

    Nissan says very little about this in the manual and after my cunfusing ramlblings above, I can see why.
    My understanding is this:

    When the meter reads below zero (as in braking or coasting) that indicates that you are charging the battery pack (supplying power to it).

    When the meter reads zero in NON-EV mode that indicates you are driving with a net zero input to the batteries.

    When the meter reads above zero you are discharging the battery pack (taking power from it) to supplement the power from the engine.

    The hybrid management software works to keep the engine in the most efficient operating RPM range as much as possible so that is why the electric motor is called upon to supplement the engine output. This comes into play when passing, quickly accelerating or under a load such as climbing a hill, etc.

    If anybody knows of anything different from the above then please pass that along.

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    Hopefully useful description.

    Full Hybrid vehicles combine functions of both series and parallel hybrid systems, and have the ability to move the vehicle with power from the IC engine, the electric motor, or a combination of both. The actual contribution from each power source depends on vehicle design and mode of operation. The engine can drive a generator to supply power to both the electric motor and the high voltage battery, or supply power to the drive wheels in conjunction with the electric motor.

    The full hybrid has a motor/generator (MG1) attached directly to the engine, and a second motor/generator (MG2) attached directly to the drive wheels. The engine, MG1, and MG2 are interconnected through a compound planetary gear set. This allows the control module to direct power from the engine or both motor/generators as required. The 2007 Altima Hybrid is a full hybrid.

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    I guess what my original question was to determine if there was actually any useful purpose for the Power Meter. As far as I can determine, the harder you push the gas pedal the more power is needed and the higher the meter reads - really don't need a meter to tell me that. The scale/tick marks are kind of bogus as the numbers don't really line up with any marks - are you using 50 kW when the needle is on the mark below the 50, above the 50 or somewhere in-between? When you brake the needle goes below the "0" into the blue - another "duh". My guess is that a tach doesn't really work with the hydrid eCVT so they had to put something in that space. Maybe a mirror would have been better so I could see the smile on my face as I get excellent fuel economy driving down the road.

  10. #9
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    Quote Originally Posted by lloyd123 View Post
    I guess what my original question was to determine if there was actually any useful purpose for the Power Meter. As far as I can determine, the harder you push the gas pedal the more power is needed and the higher the meter reads - really don't need a meter to tell me that. The scale/tick marks are kind of bogus as the numbers don't really line up with any marks - are you using 50 kW when the needle is on the mark below the 50, above the 50 or somewhere in-between? When you brake the needle goes below the "0" into the blue - another "duh". My guess is that a tach doesn't really work with the hydrid eCVT so they had to put something in that space. Maybe a mirror would have been better so I could see the smile on my face as I get excellent fuel economy driving down the road.
    well, when you are on the highway and slowing down for a toll or something, it is nice to know how much to brake to get maximum recharging. i'm under the impression that you can only charge the battery up to a certain rate (the bottom of the blue part) and braking any harder would just mean you're wasting energy to heat.

    so the power meter is good for that if my assumption is correct.

  11. #10
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    Quote Originally Posted by langjie View Post
    i'm under the impression that you can only charge the battery up to a certain rate (the bottom of the blue part) and braking any harder would just mean you're wasting energy to heat.

    so the power meter is good for that if my assumption is correct.
    Thanks langjie - so there does seem to be some use for this meter - maximize the regenerative braking that would also reduce brake wear to a minimum. I wish they would have expanded the range on the guage for the charging zone instead of the small area they now show.

    I found this over at a Prius site that seems to suggest a slow gentle braking force on the pedal seems the maximize the charging:

    http://vassfamily.net/ToyotaPrius/CAN/brindex.html

    Also this info on Wikepedia:

    The amount of electrical energy capable of dissipation is limited by either the capacity of the supply system to absorb this energy or on the state of charge of the battery or capacitors. No regenerative braking effect can occur if another electric vehicle on the same supply system is not currently drawing power or if the battery or capacitors are already charged. For this reason, it is normal to also incorporate dynamic braking to absorb the excess energy.

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