Cross-section of battery pack

Cross section of the Chevy Bolt battery pack

Looks like 5 packs of cells - I thought there was 4 of them at 15 kWh each for the 60 kWh total?

I think it is 60 kWh usable, and 5 packs at 12 kWh usable would get us to the 60 kWh

It definitely looks like 5 pack

It is five sections. The total is 60kWh, and usable is about 58kWh.

I'm not so sure. We don't have enough data yet to be conclusive, but it appears the pack is 60kWh and all that is available to the driver if desired. It also appears there will be charging feature that lets the owner set the charge to stop at 90%.

Zoomit said:

I'm not so sure. We don't have enough data yet to be conclusive, but it appears the pack is 60kWh and all that is available to the driver if desired. It also appears there will be charging feature that lets the owner set the charge to stop at 90%.

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The entire pack is never available, there is always a buffer on both the bottom and top. Some manufacturers release that info (BMW, for example), others do not and it is not clear on what the pack size refers to - actual or usable.

There is a term for completely discharging a Li-ion battery - "Bricking". Once you do it, your battery is about as useful as a brick for powering a car (or anything for that matter). The BMS will shut the car down completely before you can fully discharge your battery pack.

From the published reports on the Monterey to Santa Barbara, journalists reported figures like 58.7 kWh used (with range remaining). This is a pretty good indication that the usable energy is 60 kWh hours (or even a little more). The physical pack capacity is unknown.
It appears that Nissan makes about 97% of the LEAF pack available - and that may be part of the degradation issues they have (along with lack of thermal management).
Of those that publish actual/usable - BMW allows 87%, Kia 88%, Chevy (on the Volt) 75%.
I think it very likely that Chevy will have at least a 10% buffer, so actual pack capacity is likely 66+ kWh.

There were early reports that LG was supplying 55 Ah, 3.75 V 3P96s cells in the Bolt pack (which has 288 cells). That would yield 59.4 kWh. I believe they have gone to a 65 Ah cell (from info on the new 40 kWh Zoe). That would yield a 70.2 kWh pack and an 85% utilization.
There also some indications LG has or had a 63.35 Ah version that would yield a 68 kWh pack and 88%.

The diagram in the original post is misleading - there are 96 cell groups with 3 cells per group. While it appears that there are 5 "packs", the rear two stacked "packs" (at least the top one) are narrower.

Good points-- interesting speculation on the cells and usable battery percentages.

No doubt you've seen the few inferences or reports that there will be a 90% charge limit settable by the user. Do you know why they would do that if the usable battery capacity already has a 12-15% buffer against the real limit?

Zoomit said:

Good points-- interesting speculation on the cells and usable battery percentages.

No doubt you've seen the few inferences or reports that there will be a 90% charge limit settable by the user. Do you know why they would do that if the usable battery capacity already has a 12-15% buffer against the real limit?

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1) Living at the top of a hill (or start most trips with a significant downhill grade)
2) Some owners are willing or want to actively manage the battery charge percentage to help reduce battery degradation. Most of this stems from the LEAF and it's awful reputation for loss of range.

DucRider said:

2) Some owners are willing or want to actively manage the battery charge percentage to help reduce battery degradation. Most of this stems from the LEAF and it's awful reputation for loss of range.

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It's not just the Leaf. Tesla allows you to set the charge level less than 100% as well. It's just a fact that lithium batteries like to be around 40-60% charged. Any more, and you are adding some amount of stress. Above 80%, and the stress grows even more. 90% of the usable charge is probably about 80% of the total capacity (just guessing).

Most people drive less than 40 miles for 300 days out of the year. So why does the Bolt always need to be charged to 100%?

GetOffYourGas said:

DucRider said:

2) Some owners are willing or want to actively manage the battery charge percentage to help reduce battery degradation. Most of this stems from the LEAF and it's awful reputation for loss of range.

Click to expand...

It's not just the Leaf. Tesla allows you to set the charge level less than 100% as well. It's just a fact that lithium batteries like to be around 40-60% charged. Any more, and you are adding some amount of stress. Above 80%, and the stress grows even more. 90% of the usable charge is probably about 80% of the total capacity (just guessing).

Most people drive less than 40 miles for 300 days out of the year. So why does the Bolt always need to be charged to 100%?

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I said the LEAF battery degradation was the root cause for much of the concern. AFIK, Tesla owners do not have anywhere near the degradation problems of the LEAF, whether are not they charge to 100% regularly (I believe most do) or some lower value.

So the extra limit would just be margin on top of margin, which I can understand. It will be interesting to see how GM describes this capability and how they "teach" drivers to use it. Because GM is liable for the battery warranty, they want everyone to use a lower limit but if they use too harsh or scary language they risk backlash that the car is not really capable of the advertised range. (Similar to the 80% vs 100% limit on the LEAF)