The Bolt has at least 10% unused battery capacity?

[EldRick]

Just throwing this out there, for those who think Chevy engineers are not smart enough to charge the Bolt to less than the maximum capacity of the battery.

"The next morning, the Bolt had absorbed 68 kW-hrs of energy, the Tesla, 64.7. Is the Bolt’s charging that much less efficient? (For those of you without electrical engineering degrees, absorbing more energy is a bad thing, an indicator of inefficiency, similar to spilling gasoline at the pump, but instead it’s wasted electrons.) However, this was not the case. The Bolt’s battery is evidently larger than claimed, its usable size likely larger than its stated, 60 kW-hrs capacity (which I had run extraordinarily low; GM says a typical charge is 66.6)."

Source: http://www.motortrend.com/news/chevrolet-bolt-tesla-model-s-60-range-charging-travel/

 

[WetEV]

The Bolt has at least 10% unused battery capacity?

If the usable size of the battery is 60kWh, and the net charging efficiency is 90% (it is probably less than this), then the power required to charge would be around 66kWh. So 68kWh is about correct if the battery has 60kWh of usable capacity.

 

[EldRick]

It is not clear to me how they measured "capacity", which is the usual issue with discussing it.

 

[michael]

The only way to accurately measure a battery's total capacity is in isolation, following an established procedure. Energy used during a full charge cycle is only an indirect measure of usable capacity, since charger efficiency and the amount of energy used in thermal management is not known.

Presumably the magazine used L2 charging, so I would expect efficiency to be well under 90%, measured as energy out of the battery divided by energy out of the wall socket. This would include charger efficiency, energy used in TMS, and energy lost to heat in the battery, both during charge and discharge.

I'd guess the number is nearer 85%.

Using this definition, INL measured charging efficiency of the Leaf to range from 90% to 81% at Level 2, and as low as 61% at Level 1. Basically, the slower you charge it, the lower the efficiency (more energy wasted over a longer time). Since the Bolt will take something like 10 hours at L2, the efficiency might be well under 90%

 

[sgt1372]

So, does this mean you can "fully charge" a Bolt every day at home w/o worrying about overcharging it or is it still advisable to engage the Hilltop Reserve feature to limit recharging to 90% of whatever the usable capacity of the battery is?

 

[LeftieBiker]

So, does this mean you can "fully charge" a Bolt every day at home w/o worrying about overcharging it or is it still advisable to engage the Hilltop Reserve feature to limit recharging to 90% of whatever the usable capacity of the battery is?

If you don't need every bit of available range, I'd suggest using Hilltop Mode. 90% SOC is still pretty high for a lithium battery, while 80% is quite a bit better. The Leaf used to have a charge to 80% feature, before the EPA spanked Nissan for it with a revised range estimate.

 

[sgt1372]

So, does this mean you can "fully charge" a Bolt every day at home w/o worrying about overcharging it or is it still advisable to engage the Hilltop Reserve feature to limit recharging to 90% of whatever the usable capacity of the battery is?

If you don't need every bit of available range, I'd suggest using Hilltop Mode. 90% SOC is still pretty high for a lithium battery, while 80% is quite a bit better. The Leaf used to have a charge to 80% feature, before the EPA spanked Nissan for it with a revised range estimate.

I sometimes need 100% of the effective range to drive to/from the City (150-170 miles RT) but only occasionally (1-2x's/month at most).

So, I'll plan to use the Hilltop Reserve for at home charging normally and, when I plan to drive into the City, I'll turn it off so that it can fully charge overnight. I understand it's advisable to do this periodically anyway to make sure that the charge remains "balanced" between the battery cells.

 

[LeftieBiker]

I sometimes need 100% of the effective range to drive to/from the City (150-170 miles RT) but only occasionally (1-2x's/month at most).

So, I'll plan to use the Hilltop Reserve for at home charging normally and, when I plan to drive into the City, I'll turn it off so that it can fully charge overnight. I understand it's advisable to do this periodically anyway to make sure that the charge remains "balanced" between the battery cells.

Sounds like a good plan. My 2013 leaf seems to do some balancing when charged to the 80% limit, but occasional 100% charging also seems to help range. When you charge to "100%", try to have the charge end no more than a few hours before you leave, especially in hot weather.

 

[jjr]

It would be nice to get some numbers from GM - the only thing we've ever heard from them is 60kWh, and I don't recall GM ever stating if that was usable or total capacity.