14.7 kw hour full charge?

Temperature is key. As the temp increases you’re gonna see greater range. Purchased my car in early March in Kansas and range was typically in the mid 40’s but now with the temp usually above 70 I’m seeing ranges in the high 50’s. Last 2 days temp has been up around 80 and full charge range was only 54 both days. Battery storage follows a bell shaped curve.


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You're mixing up two very different things.

1. When charging from the wall, there is some loss because -- to cite the Second Law of Thermodynamics -- "No reaction is 100% efficient". A 15% loss for charging the car, meaning an 85% efficiency in charging, would be perfectly normal. I've seen claims for better efficiency, up to 92% efficiency, but I think that is only for short periods, not for fully charging the battery pack. If I recall correctly, as the battery pack approaches full charge, the charging efficiency drops. Anyway, charging is generally described as being between 85-92% efficient, so a 15% loss in charging is within the normal range.

An 85% (or even 92%) charging efficiency doesn't mean the battery can't be charged to 100%*; it just means that if your battery pack is rated at 17 kWh (which is what is advertised for the Clarity PHEV), then in theory it would take perhaps as much as 20 kWh to fully charge the pack. But in practice it should never take that much, because the car isn't designed to allow the battery pack to be either fully discharged or fully charged. If the usable capacity is 14 kWh, as Jdonalds says, then 14.7 kWh from the wall is absolutely nothing to worry about, and in fact that would be 95.2% efficiency, which is highly unlikely. Much more likely is that the amount of energy actually added to the battery pack is less than 14 kWh, perhaps something between 12.5 kWh and 13.3 kWh.

*That is, 100% of usable capacity, which will always be less than 100% of full capacity, to avoid prematurely aging the battery pack. Confusing, I know, but what the car's instrument panel displays as "100% charge" isn't actually 100% of what the battery cells are rated at by the battery manufacturer; it will be at least a few percent less.

2. Regarding the energy stored in the battery pack, PHEVs (such as the Clarity PHEV) are designed to maintain a minimum charge, both to ensure a certain baseline of battery power will be available on demand when needed for strong acceleration and hill-climbing, and also to avoid prematurely aging the pack, which happens when it's repeatedly drained to 0% or nearly so. It has been widely reported that the Chevy Volt tries to maintain a minimum 30% charge. I'd be surprised if the Clarity PHEV's minimum charge is much less than that. 25% is plausible, but only 15% is not. I seriously doubt anyone designing a production PHEV is going to design the car to allow the battery pack to fall to only a 15% charge under normal circumstances.

Please note that subject #2 has absolutely nothing to do with the charging losses described in subject #1 above. It's more or less a completely different subject.

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I am not arguing since I am not an expert on charging. But my Prius Prime draws 6.2kWh from wall with an 8.8 kWH battery and EPA rated as 25 miles range. That is 133 MPGe. 6.2/8.8 means only 70% of the capacity is used.

Back to Clarity, 14.7/17=86%. Apparently Clarity uses more capacity than Prius. I assume that for the same EV mileage, Clarity needs only half of the charge cycles.

 

But at least some of us, perhaps most of us, don't think it's 14.7 kWh. We think 14.7 kWh is what is drawn from the wall, but approx. (14.7 x 0.85 =) 12.5 kWh (or very slightly better) is what is stored in the battery pack. 12.5 / 17 = 73.5%, which would be a reserve of 26.5%. That appears believable for the Clarity PHEV; only 14% reserve for a PHEV does not.

Keep in mind that for a PHEV, a low battery (let's say, less than 20-25%) doesn't just mean you're cycling the battery harder than is good for battery life. For a PHEV, it also means the amount of power provided by the battery for acceleration is severely limited. PHEVs use a weak gasoline engine, one which needs an assist from the battery pack's power for strong acceleration. If the battery was drained to only 14-15%, you should notice a significant drop-off in the car's maximum acceleration. If you're not noticing any such drop-off, then you can be pretty sure the battery has not been drained that low.

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Here is what I posted at priuschat forum.

As I was looking for real efficiency of plug in hybrid cars, I felt that 25 mile range for 8.8kWh battery on Prius Prime is mediocre at best even though it has the highest MPGe. So I realized that it is related how much battery capacity is reserved for battery longevity.

So I am curious and did some simple calculation based on EPA range and EPA MPGe of some plugin hybrids.

-------------Battery Size--Range---MPGe----Used--Reserved
Prius Prime----8.8---------25-------133------0.72-----0.28
Clarity---------17----------47-------110------0.84-----0.16
Volt------------18.4--------53-------106------0.91-----0.09
Ioniq-----------8.9---------29-------119------0.92-----0.08
Fusion Energy-7.6---------21--------97-------0.96-----0.04

You can tell that Prime reserves most capacity than other cars and Clarity is next to it.

 

I don't know how you arrived at those figures, but I don't think the correct procedure was used. For example, the Volt is reported to have about 30-35% reserve capacity when new, which for an 18.4 kWh battery pack would be ~5.52-6.44 kWh.

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Volt EV range is 53 miles, and MPGe is 103, which means to drive 103 miles, it draws 33.6kWh. All numbers are EPA rated.

 

MPGe ratings include charging losses. Actual capacity, either usable capacity or full capacity, is less.

According to the image of an EPA window sticker posted at this InsideEVs article:

2016 Chevrolet Volt
53 miles of EV range
106 MPGe
31 kWh / 100 miles

31 kWh/100 miles = 0.31 kWh/mile = 3.226* miles/kWh. 53 miles ÷ 3.226 = 16.43 kWh.

This indicates ~16.43 kWh of usable capacity for the 2016 Volt. If the full capacity is 18.4 kWh, that would be 89.3% used and only 1.97 kWh of reserve capacity.

*More digits indicated than are significant

* * * * *

So much for the figures indicated by the EPA sticker. However, actual Volt drivers report something rather different:

The 2016-17 Volt with a 18.4 KWH (total capacity) battery, when the Volt is driven in electric mode only 14-14.4 KWH are used so somewhere around 4 to 4.4 KWH are still in the battery when the Volt states there is no more electric range. Even when 0 miles for electric range is indicated the car will still pull electric from the battery in when it can replenish the electricity from the engiine to keep that 4-4 KWH reserve capacity in the battery.The Volt seems to have a mind of its own and will never let the battery drop to a certain level once the range indicator for electric displays 0 miles left.
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(source: GM-Volt.com forum)

4-4.4 kWh reserve from an 18.4 kWh pack would be 21.7-23.9% reserve. I'm not sure why the "experts" are claiming 30% (or perhaps more) reserve for the Volt pack; perhaps they believe GM is actually putting a ~19.5 kWh battery pack into the Volt, but only claiming 18.4 kWh.

Full capacity for a li-ion battery is a bit fuzzy anyway. Actual nameplate capacity for a battery cell, according to specs from the manufacturer, indicates charging the cell to a voltage that no EV maker would use. The EV maker would always charge the cells to a lower maximum voltage, to extend battery life.

 

Roy just can't seem to get the difference. He's not arguing... but he is.

 

If charging loss is counted, then a battery would never be charged to 100%, and it is meaningless to specify full cycle charge numbers.

 

One thing that makes it maddening to try to pin down exact numbers on EV battery pack capacity, charging, state of charge, depth of discharge, and other matters related to PEV (Plug-in EV) battery charging, is the fact that the industry doesn't have any standard for what "a cycle" represents. In practice, auto makers look at the total distance traveled and just estimate the number of "cycles" from that.

The closest we have to an industry standard for what constitutes a "cycle" in charging/discharging a PEV is an 80%-20% cycle before recharging. But that would be 80%-20% of full capacity, not usable capacity.

Nobody would regularly cycle a PEV battery pack from 100%-0% of full capacity. That would wear out the pack very rapidly indeed. In fact, the ordinary driver wouldn't even be able to do that; he would only be able to cycle between 100%-0% of usable capacity, not full capacity. Furthermore, as has been discussed rather heavily, different models of PEVs have different amounts of reserve on "the top" and "the bottom".

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If that were true in how they calculate it then all your battery capacities would need to be increased from what you are showing to reflect that additional power required to get to full charge. There is no way to justify % of battery utilized by using the inefficiency of charging in your calculation. That lost charge is only taken into account for cost to operate.