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Discussion Starter #1
I think it would be great if GM allowed the driver to set his own depletion percentage before the ICE kicks in.

I'm sure that 30% was chosen for a reason, but i'm not sure what that reason is. The only thing i can think of is maybe that it increases the life of the battery or that it makes it less noticable to the driver when the battery starts to lose charge over it's lifetime.

If 70% of the battery gets you 40miles then 90% should get you a little over 50miles of AER. If you're a person who's commute is 40-50 miles to work every day this will change the ICE usage from daily to almost never. And if you drive slightly over 50miles daily it slash your ICE usage.

Say you have a 55mile commute. with 40 miles you'd use your ICE for 15 miles but with a 50 mile range you'd chop 66% of your ICE usage off of that.

I understand that even after depletion the battery is still used for power bursts when needed, but I would think that a spare 10% charge would be way more then enough to get the job done, and at opportunistic times the ice would recharge to 10%

I think the main reason for setting the depletion point to 30% is so that 10 years down the road when the battery isn't working at 100% it will still be working at at least 80%, so from a customer perspective it's still working 100% like new. I understand that logic but it's absolutely rediculous.

I suggest that GM make the factory preset depletion point 30% or whatever percentage for whatever reasons they want, but then allow the customer to change that depletion point to as low as 5%-10%. The difference here is that the 5-10% that the owner sets would be 5-10% of the battery's still functioning capacity. For example if the battery is getting old and holds 10% less charge then when it was new, then the customer set depletion point would be the percentage of the remaining 90% charge. This way you'll never run out of juice in an aging battery even though you've lowered the depletion point.

Over-charging Volts could be like over-clocking cpus!!!!!

If GM is worried that this will be be detrimental then perhaps they could make information public as to the adverse affects it could have on your vehicle. If need be, void the warranty if the customer decided to do it, but still, why not give the option... To have that much extra capacity in your car and not use it is crazy!

Thoughts?
 

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Did anyone bring up the fact that what they are saying now goes against the furnace-like charging graph they showed a few months ago? In that charging situation the ICE came on when it got to the low setpoint and turned off when it got to the high setpoint. So which is it?

GM, please answer the following (if you want to of course):

1) Is the generator directly connected to the motor in such a way that the battery can be completely disconnected?

2) If there are two different paths to power the motor how do they work together?

Thank you for the clarification.



I still think the software guys will come up with several mode of operation depending on the driver and driving conditions. There are just too many different conditions to be satisfied with one mode. I guess we will have to wait and see. At this point event the software guys might not know. They will need the final pre-production drivetrain hardware to really start knocking out the V1.0 code.
 

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At the Volt Nation event in NYC, I suggested to one of the engineers (I don't remember his name) that they tie the ICE threshold (normally 30%) to the car's GPS system. Since the battery at 30% still has about 15 miles of charge left, I suggested that they try something like lowering the threshold to 20% if the Volt was within 5 miles of my home. That would delay the time at which the ICE came on, and maximize the time driving on pure electric.

The engineer chuckled and said "we already thought of that, and I can't say anything else."
 

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The following is based on the information that was posted today regarding Customer Depletion Point

The set points seem to be similar to the Toyota / Lexus set points. The reason they do it is battery life. They discovered that charging the battery to 100% and letting it get close to zero will shorten battery life. However GM seems to have decided to allow the battery to drain below the 30% level on long hill climbs. I would think that allowing the battery to manually or automatically be boosted to over 30% prior to a hill climb will enhance battery life.



Now it seems to me that GM is going against what Toyota is doing. From what I understand by not starting the charger till 30% the battery will drop below 30% to maybe 20% and below. If someone lives on the top of a high hill they would consistently deplete the battery to 20% or even 5% every day when they come home. Toyota seems to have figured out the secret to long battery life is don't go below 30%. The Prius taxi cabs have batteries with over 200,000 miles on them. I would think that GM would want to follow and use what Toyota has learned to extend battery life

Maybe GM is doing this and does not want to let the competition know their plans
 

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Over-charging Volts could be like over-clocking cpus!!!!!
Ummmm. . . no.

Overclocking a CPU isn't based upon reaching a certain capacity. The speed capability of a CPU is based largely upon the propagation delay of the transistors that make up its logic elements. A simplistic explanation is that the groups of transistors in the various logic elements must be able to switch from one state to another within the clock cycle time. If you increase the frequency of the clock to the point where the transistors don't have enough time to switch properly, the CPU fails to operate properly.

A good portion of the "overclockability" of a CPU is based on its process design. You can increase the voltage to the CPU, which increases the current available to help the transistors switch faster, but this also increases the heat generated. This is why keeping an overclocked CPU cool is critical. Excessive heat will shorten the life of a CPU susbtantially. Regardless of how cool you keep it, if you over-volt the CPU too far, the excessive voltage will punch through the oxide insulation layer in the transistors, causing them to fail irreversibly.

Another simplified explanation: the battery pack storage capacity is determined by a chemical reaction, with the chemicals in one state (charged) or another state (discharged), or somewhere in between. When charging the battery, the cell chemistry is such that once all of the chemicals have reversed back to the charged state, there is no "place" for the excess charge to go. Continuing to charge the battery will result in excess heat generation, and will damage or destroy the battery. If you want to try this, be my guest.
 

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I'm concerned that the depletion algorythm discussed today won't work for my long driving trips.

I like to drive soutn froM San Jose California to San Diego. About 400 miles out, I get to the Grapevine, which is the mountain pass that you have to cross to get to LA.

I'm concerned that if I get to the base of the Grapevine at 30%, I won't have enough juice to maintain speed all the way to the top.

Given what you've read on the subject, what do you think?
 

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Discussion Starter #7
Altazi,
I didn't mean overcharging would be like overclocking so literally. I meant it only in that knowledgeable customers could choose to exceed the factory designed threshold. But guilty as charged it was a bad analogy.. and by over-charging I didn't really mean over charging, i just mean setting the depletion point lower so that more of the charge is usable.
 

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Altazi,
I didn't mean overcharging would be like overclocking so literally. I meant it only in that knowledgeable customers could choose to exceed the factory designed threshold. But guilty as charged it was a bad analogy.. and by over-charging I didn't really mean over charging, i just mean setting the depletion point lower so that more of the charge is usable.
Got it. My bad for being too literal. That's just me, though. I couldn't see your smile as you were typing.

I do think that the term "customer depletion point" is awful. I thought it applied to what happens if GM sets the Volt's price too high. . . ;)
 

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If they have GPS then shouldn't the system have the ability to know the needs for the terrain?

Put it this way. If you are in an area of steep grades couldn't the system figure that it needs to run the genset at a higher RPM and try and set the SOC at higher than 30%? It seems like a programmer should be able to easily accomplish that task.
 

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Did anyone bring up the fact that what they are saying now goes against the furnace-like charging graph they showed a few months ago? In that charging situation the ICE came on when it got to the low setpoint and turned off when it got to the high setpoint. So which is it?
The Customer Depletion Point update today was pretty confusing and badly worded. What it looks like to me is that the genset will provide the average output needed to keep the car moving, with peak power demand supplied by the battery, and excess power recharging the battery. So in most situations I think the battery will slowly get charged up until it reaches a set point and the genset switches off. If you drive like a maniac or power up a mountain then then maybe not.

I'm just speculating here so we'll have to wait and see.
 

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I like to drive south to San Diego from San Jose on I-5. There is this nasty thing called the Grapevine in the way.

Somehow, as I am driving along on the extremely flat and uneventful interstate, I would like to tell the car that there is a mountain 100 miles away, so that it could charge up the battery from the 30% Depletion Point, so that I would have sufficient power to climb the hill the way I want to.

I hope that isn't too much to ask. :D
 

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I like to drive south to San Diego from San Jose on I-5. There is this nasty thing called the Grapevine in the way.

Somehow, as I am driving along on the extremely flat and uneventful interstate, I would like to tell the car that there is a mountain 100 miles away, so that it could charge up the battery from the 30% Depletion Point, so that I would have sufficient power to climb the hill the way I want to.

I hope that isn't too much to ask. :D
I think you're assuming there is a problem that may not even exist. Actual performance specs for the battery, motor, controller and ICE/generator have not ever been released. I believe that the goal they are shooting for is to have the ICE have enough power to get you up the Grape Vine without using any battery power. The only time that the controller will dip into the battery on the way up the hill is when you want to pass a slow moving truck or something. I guess if you insist on climbing the hill with the pedal floored and going 85 or 90 up the hill then you will no doubt hit a point in the battery depletion where the controller will over ride your high speed desires and govern you down to what the ICE can handle. In the interest of long battery life, I think this is reasonable.

I'm sure that GM is well aware that America has many long uphill grades along it's many highways, some of them worse than the Grape Vine. I would prefer to assume that GM's team has done their homework, run numerous calculations, and come to the conclusion that the ICE and generator will be able to conquer America's hills without much battery assist. Others here really seem to want to doubt their ability to make a workable car and want to re-engineer the car that doesn't even exist yet with WAGs and off the top of the head calculations. I think it's way, way, way too soon to be debating GM's engineering choices without any intimate or substantial details on the performance or workings of any of the Volt's systems or components.

I believe that we should give the Volt team a shot at making a workable sedan that we can all love, see the real world results and then start debating what GM should do to correct problems. I hope that's not too much to ask.
 

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I like to drive south to San Diego from San Jose on I-5. There is this nasty thing called the Grapevine in the way.

Somehow, as I am driving along on the extremely flat and uneventful interstate, I would like to tell the car that there is a mountain 100 miles away, so that it could charge up the battery from the 30% Depletion Point, so that I would have sufficient power to climb the hill the way I want to.

I hope that isn't too much to ask. :D
Look at the bright side, you should be able to recoup a boatload of charge in regenerative braking on the way back down!
 
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