[smokie]

I was in Hold on the motorway today and noticed from the graphic display that at times I was using Engine, at other times Engine and Battery and once or twice Battery.

Is this how it's supposed to work? I thought Hold stopped it using battery at all.

 

[black_amp]

The Ampera is much cleverer than that, in hold mode your battery stays where it was when you engaged the hold, if you recovered energy down a hill or stopping, that energy goes into a buffer the car uses that energy to delay the starting of the engine saving fuel and wear and tear.
Your car is working as it should, you can see the buffer build up as a white bar on top of the green bars in the GOM you'll only see it if you have a long steep hill to regen down in L mode

 

[HandyAndy]

... never seen this white bar myself, but mine's a MY2012, so maybe predates that feechur.

Also, if you hoof it in Hold mode, you could use more than 75 hp's worth of power (Leccy motor(s) combine to supply up to 150 hp) which will inevitably drain the traction battery, as the ICE can only supply about 75 hp max qty of leccy. So you still have 150 hp when you really want it, though you'll notice the ICE keeps revving away after you ease off, ro get the battery back to the level it was at earlier.

The car tries to run the ICE as efficiently as possible, so you'll notice it running the ICE for a while and it's probably generating more leccy than you're using on a gentle section, so this raises the battery level, and after a while it will cut the ICE and use up the "excess" leccy stored in the battery. All very clever stuff!

 

[Jack]

 

[donald]

The engine has specific 'set points' that are tuned and designed to run at maximum efficiency. The car can run its engine at [IIRC] 12kW, 18kW, 22kW, 28kW and a couple of higher powers when you boot it.

If you are averaging between 12kW and 18kW then the engine will change between those two power settings to try to match the energy it is generating to what you are using. Likewise for an 'average' power consumption between the other settings.

For example if you are straight and steady at 15kW then half the time it will run the engine at 12kW and draw 3kW from the battery, and the other half it will run the engine at 18kW and recharge the battery at 3kW.

Does this give you the 'theoretical' overview you're looking for?

If you are averaging less than 12kW, then it will turn off the engine once it has charged up its small 'engine buffer' of battery charge (around half a kWh) and then start it back up again once that buffer is consumed.

It is better to keep the engine running rather than turning it on and off. This is for a couple of reasons related to how it changes its operating modes. But the upshot is that it is actually better to drive at around 65mph, which should keep you just above 12kW drawn without losing too much efficiency due to speed, and this will result in efficiency benefits.

 

[smokie]

Wow, thanks for the detailed responses, you've more than answered my question but it is fascinating. This is such a cleverly designed car isn't it. I'm going to print this to try to digest it, as I have some mates (one or two more technical than me!) who are really curious about the way it operates, and also I want to operate the car efficiently, without getting too anal about it!! I'll look for the white bar next time I'm on a run...

 

[Spiny]

Its a computer with clever programming to which someone bolted 4 wheels on, If your kind to it you "may" be allowed to drive it though mainly only to point it in the desired direction. The car has a display system designed to keep the passenger(s) occupied and distracted whilst it gets on with the task of controlling the energy flow efficiently.on the move.

Now just think what the Ampera would be like if it was autonomous!

.

 

[Rob Davies]

... never seen this white bar myself, but mine's a MY2012, so maybe predates that feechur.

Also, if you hoof it in Hold mode, you could use more than 75 hp's worth of power (Leccy motor(s) combine to supply up to 150 hp) which will inevitably drain the traction battery, as the ICE can only supply about 75 hp max qty of leccy. So you still have 150 hp when you really want it, though you'll notice the ICE keeps revving away after you ease off, ro get the battery back to the level it was at earlier.

Sidebar: my understanding is that only the larger motor (MGB) is used to drive the car, except at higher speeds when using both MGA and MGB improves efficiency. MGB is 110kw (=150hp) on its own. Which raises an interesting point. Voltec 2 cars have two, smaller, motor/generators, but both can be used at once to provide a combined power which is greater than Voltec 1 vehicles. Which means it would be theoretically possible to combine the powers of both motors in a Voltec 1 to make a 225hp car. Which would be interesting. Just an amusing thought.

 

[donald]

Sidebar: my understanding is that only the larger motor (MGB) is used to drive the car, except at higher speeds when using both MGA and MGB improves efficiency. MGB is 110kw (=150hp) on its own. Which raises an interesting point. Voltec 2 cars have two, smaller, motor/generators, but both can be used at once to provide a combined power which is greater than Voltec 1 vehicles. Which means it would be theoretically possible to combine the powers of both motors in a Voltec 1 to make a 225hp car. Which would be interesting. Just an amusing thought.

It doesn't work quite like this.

What happens is that as soon as the conditions are right to engage both motors, then it will. This is steady speeds, mid-torque above ~35mph. In electric mode it changes into this mode quite quickly, it seems to take a little longer if the engine is running.

If the bigger MGB were to throw in its full power then it'd push MGA backwards, the two have to be torque-balanced to both deliver useful power into the differential epicyclic set that combines them.

This means you only get twice the lower power motor, MGA, which happens to be 55kW. So at full power in CD2, which is only momentarily, you'd get twice the MGA's 55kW = 110kW. But in this case the gearing is against you so what actually happens is the clutches change and lock out MGA and all the power comes from the 110kW MGB motor.

If the engine is running with both motors engaged, the same thing happens: in this configuration the motor and MGA add together, both being 55kW, so giving 110kW total. MGB is, in this mode, essentially idling and only produces reaction torque (and rotational velocity, which allows the engine speed to vary) on the straight-and-level to stop it spinning. When more power is needed, MGB will apply additional torque to counter the additional torque of the combined MGA + engine, but only up to 110kW. In the Cadillac ELR, it will actually allow an exceedance of 110kW by adding in the MGB motor power too, up to the torque limit to balance across the epicyclic. But Volt/Ampera has been designed to deliver 110kW in all situations, hence the MGA+engine are each a half of the maximum power rating.

MGB also acts as the regenerator when MGA+engine are running, so if for example you are going downhill with the engine running in CS2, MGA would still be generating power from the engine, whilst MGB would then be regenerating what is left from the actual descent of the hill.

 

[Marli]

MGB also acts as the regenerator when MGA+engine are running, so if for example you are going downhill with the engine running in CS2, MGA would still be generating power from the engine, whilst MGB would then be regenerating what is left from the actual descent of the hill.

This seems the obvious solution after you read it, but it wasnt how i thought it worked. This car is SO well designed.

 

[Rob Davies]

It doesn't work quite like this.

What happens is that as soon as the conditions are right to engage both motors, then it will. This is steady speeds, mid-torque above ~35mph. In electric mode it changes into this mode quite quickly, it seems to take a little longer if the engine is running.

If the bigger MGB were to throw in its full power then it'd push MGA backwards, the two have to be torque-balanced to both deliver useful power into the differential epicyclic set that combines them.

This means you only get twice the lower power motor, MGA, which happens to be 55kW. So at full power in CD2, which is only momentarily, you'd get twice the MGA's 55kW = 110kW. But in this case the gearing is against you so what actually happens is the clutches change and lock out MGA and all the power comes from the 110kW MGB motor.

If the engine is running with both motors engaged, the same thing happens: in this configuration the motor and MGA add together, both being 55kW, so giving 110kW total. MGB is, in this mode, essentially idling and only produces reaction torque (and rotational velocity, which allows the engine speed to vary) on the straight-and-level to stop it spinning. When more power is needed, MGB will apply additional torque to counter the additional torque of the combined MGA + engine, but only up to 110kW. In the Cadillac ELR, it will actually allow an exceedance of 110kW by adding in the MGB motor power too, up to the torque limit to balance across the epicyclic. But Volt/Ampera has been designed to deliver 110kW in all situations, hence the MGA+engine are each a half of the maximum power rating.

MGB also acts as the regenerator when MGA+engine are running, so if for example you are going downhill with the engine running in CS2, MGA would still be generating power from the engine, whilst MGB would then be regenerating what is left from the actual descent of the hill.

My brain hurts.