80% of what?

[Red]

I had assumed that it meant 80% of the batterys total capacity (whatever that might be, reducing as the battery aged). So, to estimate the total capacity I charged the Leaf to 80% and then started a new charge cycle to bring it up to 100%. My Blink charger reports the KWh supplied for the last charge cycle, so I figured I would know how much energy was required to charge the battery 20% (100%-80%).

Turns out the answer was 2.9KWh. Multiply by 5 to Get 100% and it looks like I have a 14.5 KWh battery, even though it still shows 12 bars.

What am I missing here?

 

[johnqh]

80% is 80%, but 100% is really not 100%. It is 92% or something around there.

 

[dgpcolorado]

80% is 80%, but 100% is really not 100%. It is 92% or something around there.

Phil has measured "100%" at 94-95% IIRC.

 

[DaveEV]

I had assumed that it meant 80% of the batterys total capacity (whatever that might be, reducing as the battery aged). So, to estimate the total capacity I charged the Leaf to 80% and then started a new charge cycle to bring it up to 100%. My Blink charger reports the KWh supplied for the last charge cycle, so I figured I would know how much energy was required to charge the battery 20% (100%-80%).

Turns out the answer was 2.9KWh. Multiply by 5 to Get 100% and it looks like I have a 14.5 KWh battery, even though it still shows 12 bars.

What am I missing here?

2.9 kWh seems very low for a 80-100% charge. As others noted, 80% is truly 80% SOC, while a 100% charge is more like 95% so only about 15% more.

That said, I have seen 80-100% charges use take anywhere from 1h28m 4.97 kWh a year ago, though the last one took 1h10m 3.64 kWh. I have seen pretty large variability between 80-100% charges even a couple days apart - nearly an entire kWh and time difference of 14 minutes, so I don't think that 80-100% charge times are necessarily an accurate indicator of pack capacity.

 

[lpickup]

What am I missing here?

You are missing the "overhead"/losses of the charging system itself as the charging process tapers off as the SOC approaches 100%. So right off the bat you probably are experiencing around 15% loss in the charger as measured from the wall compared to what's actually being stored in the battery. Part of that runs the "battery fan" (or what I assume to be a battery fan--whatever it is that makes a fan-like noise when the car is charging). As the charging tapers off as you approach 100%, the fan is still running, so you will see additional loss as you approach 100% (or whatever the top end really is).

 

[DaveEV]

Part of that runs the "battery fan" (or what I assume to be a battery fan--whatever it is that makes a fan-like noise when the car is charging).

It's a water pump that circulates coolant through the onboard charger.

 

[DaveinOlyWA]

I had assumed that it meant 80% of the batterys total capacity (whatever that might be, reducing as the battery aged). So, to estimate the total capacity I charged the Leaf to 80% and then started a new charge cycle to bring it up to 100%. My Blink charger reports the KWh supplied for the last charge cycle, so I figured I would know how much energy was required to charge the battery 20% (100%-80%).

Turns out the answer was 2.9KWh. Multiply by 5 to Get 100% and it looks like I have a 14.5 KWh battery, even though it still shows 12 bars.

What am I missing here?

"IF" we take a full charge as being 281 GID for a new battery with total capacity of 300 GIDs (assuming the 80 watt hours per GID which is GREATLY disputed) then a "100%" charge is only 93.6% then your "capacity" works out to 21.32 Kwh which is not really correct either.

what gets stored in the battery (the disputed 80 watt hours) is not what you get when you retrieve the power due to losses and the 2.9 reported by Blink also has losses going in.

now, generally you can probably figure on roughly 10-12 % loss into the battery which makes your 2.9 kwh in as 2.6 stored

what it really boils down to is that we are not really provided accurate enough measuring tools to make to be that specific.

 

[planet4ever]

Part of that runs the "battery fan" (or what I assume to be a battery fan--whatever it is that makes a fan-like noise when the car is charging).

It's a water pump that circulates coolant through the onboard charger.

Actually, what he is hearing probably is a fan. As you say, there is a pump which circulates coolant through the charger (and also the DC/DC converter which powers all 12v equipment). But then there needs to be a radiator fan to cool the coolant. The pump, radiator fan, and computers can, of course, be powered by the 12v battery, but running them for hours during charging would drain that battery.

Ray

 

[kubel]

Anyone else notice when you unplug, the fan/pump noise kind of dies down for a half second and then kicks back on- as if it's switching power sources?

 

[DarkStar]

80% is 80%, but 100% is really not 100%. It is 92% or something around there.

Phil has measured "100%" at 94-95% IIRC.

?!

So... If my WattsLeft meter shows my 100% charge at 97.5% SOC, have I experienced any deterioration? (sounds like a riddle!)

 

[dgpcolorado]

80% is 80%, but 100% is really not 100%. It is 92% or something around there.

Phil has measured "100%" at 94-95% IIRC.

?!

So... If my WattsLeft meter shows my 100% charge at 97.5% SOC, have I experienced any deterioration? (sounds like a riddle!)

One of the problems with throwing around %SOC numbers is that we are often talking about two completely different things. One is what the full capacity of the battery is and the other is what the usable or allowed amount of the battery is.

IIRC, Phil* measured the top of the allowed charge of the battery at 94-95% of the full 24 kWh. The bottom (shutdown after turtle) is in the 2% range. The remainder is the usable portion of the battery and can be thought of as "0-100%" SOC from the point of view of the driver. And that's probably what the various meters try to measure.

What was interesting from Phil's research was that "80%" was really 80% of the total battery capacity. That means that charging from 80% to "100%" (94-95% actual capacity) adds less charge than the numbers would otherwise suggest. That's why I mentioned it. LEAF drivers have a tendency to extrapolate an 80% to 100% charge as being 20% of the battery and, according to Phil, it just isn't so. This helps explain why the top end of the SOC, that part above an 80% charge, seems a bit smaller than it otherwise ought to be. It is.

Hope that makes sense.


* For newcomers here: "Phil" posts as Ingineer here at MNL and runs the EVSEUpgrade.com business.