Chevrolet Bolt Start Of Production Set For October 2016?

[michael]

Balancing is usually done at the top of the charge. This is not necessarily 100% SOC (the battery's maximum capacity) but at the level to which the cells are charged.

For example, a cell might be at 100% SOC when charged to 4.2 Volts. Suppose that the charging system is designed to limit this to, for example, 4.1 V in order to extend battery life. In that case, balancing is done at 4.1 V per cell.

Although the above is the most common practice, there are other approaches. Since all the cells are not absolutely identical, even when top balanced, when the battery is discharged the weakest cell will reach the minimum allowable Voltage before the others. So an alternate approach that is sometimes taken is "bottom balancing". In this case, it's worked out so that all the cells reach the minimum allowable Voltage at the same time.

It's not clear to me what are the advantages, if any, of bottom balancing. But I think top balancing is much easier to implment

 

[mbepic]

I personally believe that Chevy has already begun 'production' of thousands of what I will call 'demo/show' vehicles that will be sent out to all the dealers, media, national & international markets to be ready for the official October introduction. These BOLT EVs are being inventoried with designated delivery points. These BOLT EVs are beyond 'test' vehicles although I believe they came from the factory that is still in 'test' mode.

If Chevy is placing some emphasis on fleet vehicles, then these BOLT EVs are being built as we speak too!

The question is whether these vehicles will actually be sold to the public at some point after they have served their purpose.......maybe some, maybe all.

I think they have learned from their experience with the Chevy Volt that in order to sell EVs, they have to ensure that dealers have the sufficient cars to 'demo' to the public.

That is my belief and opinion at this point.

 

[ssspinball]

There is absolutely no need for a Bolt (or any EV owner) to be concerned about charging to full or driving to empty. The car manufacturers are not dumb and wouldn't put 8-10 year warranties on batteries if they didn't already do proper testing in worst-case scenarios. Charge it to full nightly without worry.

The only exception is those few EVs (Telsa, MB B-Class) that allow you to optionally enable use of the "reserve" buffer but you have to toggle that on each time you use it. Obviously you shouldn't do that every day, but you can still charge both of those to full without worry.

Interesting anecdote: My i3 will run it's battery cooling system if my garage gets too hot inside even though the car is just sitting there with no one in it. It is obvious because I can hear the fan running.

 

[elpwr]

Maybe you can fully charged and discharge your Bolt battery without "worry", but it will result in faster degradation. That's an established fact. And remember, the 8–10 year battery warranty covers failure but not normal degradation.

The Tesla does not have a "reserve" that you toggle. . I can set my Tesla to charge anywhere from 50 to 100%. Tesla recommends using 80% for daily charging to preserve the battery. Tesla recommends 100% charge to be used only when necessary - like for road trips.

I'm hoping the Bolt will allow adjustment of charge percentage like Tesla. My Spark EV does not have this option.

 

[Devin]

Maybe you can fully charged and discharge your Bolt battery without "worry", but it will result in faster degradation. That's an established fact. And remember, the 8–10 year battery warranty covers failure but not normal degradation.

The Tesla does not have a "reserve" that you toggle. . I can set my Tesla to charge anywhere from 50 to 100%. Tesla recommends using 80% for daily charging to preserve the battery. Tesla recommends 100% charge to be used only when necessary - like for road trips.

I'm hoping the Bolt will allow adjustment of charge percentage like Tesla. My Spark EV does not have this option.

Early Nissan LEAFs had an 80% charge option but it turned out not to have much effect on battery longevity - heat was the primary issue - so Nissan removed the option in 2013 (if I recall). All non-Tesla cars have a reserve that is not accessible, i.e. the Nissan LEAF allows you to use 21kWh of its 24kWh pack. It is significantly worse for a battery to be discharged to a very low level than it is to be charged to a high level.

Other Tesla-based cars (the RAV4 EV and Mercedes B-ED) do have a reserve that you toggle. In the RAV4 a "normal charge" is 35kWh while an "extended charge" is somewhere around 41kWh. Here's what the selection looks like on the RAV4:

 

[elpwr]

Frequent 100% charges have a significant adverse effect on battery longevity; especially at warmer temperatures and for prolonged periods. Lithium ion batteries are fussy creatures. They don't like to be too highly charged nor too far discharged. They don't like to be too hot nor too cold. Many of them are only rated for 1500 – 2000 full charge/discharge cycles. But that can be extended to many thousands of cycles when not fully charged/discharged and kept at moderate temperatures. This ideal can't always be achieved in automotive applications. But when you can observe it, you will help minimize degradation.

Within reason, I have tried to follow these suggestions; and my nearly 3 year old Tesla with 26,000 miles on it is showing less than 2% battery degradation. Some other Tesla owners that routinely push their batteries harder are showing two or three times as much capacity loss at 3 years. This is probably not much of an issue if you plan to lease the car for three years. But if you are purchasing it for the long run, it might be worth thinking about.

 

[Devin]

I don't think anyone is disputing the fact that frequent 100% charges cause accelerated degradation. However, only Tesla vehicles (and their derivatives) are capable of charging to or very near to true 100% capacity. All other manufacturers hide capacity as a buffer to prevent this degradation. Tesla gives the user the option. One approach isn't inherently better than the other. Traditional automakers take the hidden buffer approach because it is simpler and in many cases these companies have been burnt by launching complicated infotainment systems recently. They don't want to burden the customer with making decisions that may cause material change to the car especially if they are new to EV technology.

For example: Ford Sync has been the cause of a huge amount of customer complaints and quality concerns, yet the system works well for users who are more tech-savvy. Unfortunately the ignorance of the masses means that in order for Ford not to take a hit in reviews they have to dumb down the system, as they have done with version 3. I believe that most current Tesla customers are much more savvy than your average Nissan/Ford/GM/etc buyer so they like all of the additional control over the car. It will be interesting to see if Tesla continues this approach with the Model 3, but I imagine as Teslas begin to sell to more mainstream consumers they will suffer from issues related to ease-of-use perception.

 

[elpwr]

Tesla builds in a few % of buffer at the top and bottom of the charge - a 100% charge on the screen is not a true 100%. And 0 miles at cutoff is not fully discharged. Just about all other other EV manufacturers do the same to conserve battery life. My 85kwh rated battery has been shown to have about 78-80kwh usable available capacity when new. Nonetheless, Tesla still recommends not using the full charge unless really needed. And like you've noted, deep discharges are also detrimental to the battery. Because the S85 has so much range, it's generally not too hard to avoid the extreme ends of the charge range.

My '14 Spark EV, on the other hand, has about 19.7 kWh usable from the 21.4 rated. They're pushing these smaller batteries closer to their limits to improve on their already limited range. And I have seen more range reduction in my Spark after 10,000 miles than I have in the Tesla at 26,000.

 

[ssspinball]

I don't think anyone is disputing the fact that frequent 100% charges cause accelerated degradation. However, only Tesla vehicles (and their derivatives) are capable of charging to or very near to true 100% capacity. All other manufacturers hide capacity as a buffer to prevent this degradation. Tesla gives the user the option.

+1

So again, there is no need to worry about charging a Bolt to 100%. Chevy has (so far) been more conservative than Telsa. You could also describe it as either more "foolproof" or more limited (since you don't get the option of playing with the buffer).