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Discussion Starter #1 (Edited)
Hello..... When I accelerate in ICE the yellow bar to the battery (to the left) is always at least 25% or even more longer then the yellow bar that leads to the engine (to the right). This is in the the KW display above the steering wheel. The KW zips up to 80 or even 100KW. I assume from this that more power is coming from the battery? Only while first accelerating. After acceleration the two yellow bars even out and then the battery yellow bar may go away as you cruise. I have asked this before but I do not think I explained it correctly.

IF IF the above is True do some people pay a penalty if they drive too hard in ICE. In other words does the battery switch to ICE sooner (when in full EV Mode) to maintain the safety buffer in the battery? If you drive to hard in ICE does the algorithm/Volt logic keep track of this. The KWHR reading \on the center console would say No to this. But since this KWHR reading is not a measurement I am wondering if the the above could be true.

The below link describes the 4 modes of operation, which is often simplified down to 3 modes as was done in a recent post. In post #10
http://gm-volt.com/forum/showthread.php?6611-Voltec-drive-unit-has-four-basic-modes-of-operation
 

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Yes, the battery will supply extra energy as a buffer, and the engine will play catch up. The kW on the driver dash is the total/net HV power being used at the moment. Some could be coming from battery and some from engine, that is the net difference. The engine on paper provides 55kW max - assuming that number and 110kW on the DIC you would expect 55kW from the battery.

It will also often start the engine sooner if you have high power draw, because the computer knows it needs about a minute for warmup and you can bottom out too far if it switches at it's absolute minimum point.
But it's not significant. Maybe 100-200Wh worth.
 

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Discussion Starter #3 (Edited)
Hello Tks for the reply. I do not recall any descriptions of the 2 ICE modes in any of the videos that say such a large % of power could still be coming from the battery during accelerations. Although this is alluded to in the High demand mode description of the ICE. 50% or more of the power to do heavy accelerations seems to be coming from the battery as indicated by the yellow bar on the left of the display zipping up for a few secounds to the battery icon on the display above the steering wheel. If so this means people who do heavy accelerations in ICE are using more of the safety buffer of the battery.
There is a tendency in the descripitions of the two ICE modes to minimize any possible contributions by the battery. Which is true except for in hard accelertions. It is mentioned under Mode 3 Low speed extended range propulsion (Engine running) in the below link.

http://www.greencarcongress.com/2010/10/chevy-volt-delivers-novel-two-motor-four-mode-extended-range-electric-drive-system-seamless-driver-e.html

The concept of "Low speed" in the title seems inconsistant with hard accelerations, but whatever. In hard accelerations above 40MPH (and other MPH) is when the yellow bar zips up to a 100KW, mostlly on the battery side of the display.


Yes, the battery will supply extra energy as a buffer, and the engine will play catch up. The kW on the driver dash is the total/net HV power being used at the moment. Some could be coming from battery and some from engine, that is the net difference. The engine on paper provides 55kW max - assuming that number and 100kW on the DIC you would expect 55kW from the battery.

It will also often start the engine sooner if you have high power draw, because the computer knows it needs about a minute for warmup and you can bottom out too far if it switches at it's absolute minimum point.
But it's not significant. Maybe 100-200Wh worth.
 

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The computer is trying to optimize fuel efficiency by not revving the engine too hard if it doesn't need to.
Dipping into the battery reserve helps achieve this.

However, if you accelerate too hard for too long, it will fall back to 'Propulsion Power Reduced' mode, where the max power you can accelerate with is 55kW, or the limit of the engine+generator.
It won't let you take the battery too low.

And corrected a typo above - should say 110kW = 55kW + 55kW ;)
 

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Discussion Starter #5 (Edited)
Hello I would suspect that the below does not happen on a daily commute of less that 70 miles. I do not recall seeing that happen. Maybe those who have been on long drives may have noticed less KW on thier accelerations. Or in other words, a limit of 55KW and no more 80-100KW accelerations.
I do not recall anyone here ever noting the below. I did not know this. This is something to watch for.
TKS

The computer is trying to optimize fuel efficiency by not revving the engine too hard if it doesn't need to.
Dipping into the battery reserve helps achieve this.

However, if you accelerate too hard for too long, it will fall back to 'Propulsion Power Reduced' mode, where the max power you can accelerate with is 55kW, or the limit of the engine+generator.
It won't let you take the battery too low.

And corrected a typo above - should say 110kW = 55kW + 55kW ;)
 

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Hello I would suspect that the below does not happen on a daily commute of less that 70 miles. I do not recall seeing that happen. Maybe those who have been on long drives may have noticed less KW on thier accelerations. Or in other words, a limit of 55KW and no more 80-100KW accelerations.
I do not recall anyone here ever noting the below. I did not know this. This is something to watch for.
TKS
During a daily commute, it's NORMALLY got a lot of time to make up for the occasional acceleration past the current engine output. If you floor it for 20 seconds to pass someone, the ICE revs up a little for a minute or two, and the small (I suspect about half kwh) buffer gets rebuilt. What you can't do, though, is accelerate like that for minutes at a time, or you'll run out of that buffer and get the "propulsion power reduced" message until you've given it a few minutes to recover. (Or climb a 4% grade for 10 miles on that, and that's where Mountain Mode comes in, to give you a much LARGER buffer (2-3 kwh) for climbs.)
 

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Discussion Starter #7 (Edited)
Hello hellsop. Tks for clarifying this. I misunderstood canehdian's post. The buffer is relatevly constant over a long period of time as the battery gives and recieves KW, As shown in the figures with the arrows going in both directions to the battery. So you have to accelerate real hard constantally to reach the point where you get only 50KW during accel, instead of the full 100KW. Which I have not seen that I can recall. You would have too slow down speed up repeatably till the buffer is used up. 50 KW in about 4 sec is about .055KW-hrs. So to use up the .5KW buffer that would take about 9 accelerations over a short period of time. .5KW-HR/.055=9 times. That would be hard but possible. More so possible if going up a hill in regular mode and not using mountain mode


During a daily commute, it's NORMALLY got a lot of time to make up for the occasional acceleration past the current engine output. If you floor it for 20 seconds to pass someone, the ICE revs up a little for a minute or two, and the small (I suspect about half kwh) buffer gets rebuilt. What you can't do, though, is accelerate like that for minutes at a time, or you'll run out of that buffer and get the "propulsion power reduced" message until you've given it a few minutes to recover. (Or climb a 4% grade for 10 miles on that, and that's where Mountain Mode comes in, to give you a much LARGER buffer (2-3 kwh) for climbs.)
 

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It's not common to exhaust the buffer in typical flat/small hill conditions.
It's sustained uphill at high speeds that will do it, and is what mountain mode was made for.
You have to try pretty hard to get to PPR under normal driving circumstances, unless you live in the mountains and like to drive fast.

The engine will rebuild the buffer whenever there is excess energy available.
So unless you drive >55kW forever, it will eventually recover.
Bursts of accel 9 times likely still would not exhaust it because it has time to recover between them.
 

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Discussion Starter #9 (Edited)
Hello Tks for making the below clarification. I did think about the below, but did not clarify that the 9 times had to be instaneous. I was just looking for some kind of relative number. It could take anywhere from12-30 accelerations to exhaust the buffer. Who knows. The answer is probally some kind of fuzzy math. Or better yet someone that has done so on the actual road. Someone that has access to the GM algorithm could do the real math more accuratelly. All i can do is take pot shots at the Truth and hope its close.

If anything else I think this thread clarifys some aspects of mountain mode with the 2-3 vs normal .5KW buffer. At least for me.
Even if it may seem a bit anal (i mean analaytic) to some.

What drove this question was my Ev miles are a bit low cause of the summer heat. 38-40 when driving 45-60MPH. I was wondering how much the actual point where the Engine turns on varies. And if that line is effected by how hard people drive in ICE. If the GM algorithm adjusts this line to protect the battery.

Bursts of accel 9 times likely still would not exhaust it because it has time to recover between them.
 

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That transition line is very tight, within 1% or so of the set endpoint (by the calculated state of charge, SOC). From a user's standpoint it's less of an impact on range than temperature, terrain, etc.
The only significant change in engine on transition/buffer size is by enabling mountain mode.
 
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