Clarification wanted on how quick charge works

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BetaMark

Active member
Joined
Oct 28, 2010
Messages
34
Location
Van Nuys, CA
All,

The literature says that using quick charge (or DC charge, or L3, or whatever you call it), the Leaf can be charged from zero to 80% of full charge in 30 minutes.

So let's say I have a 50% charge (presumably meaning a 50-maile range, if this is linear). Would I be able to QC to 100% charge in less than a 1/2 hour?
 
I thought it would be more like take 15 minutes to charge from 50% to 80% because the last 20% is always very slow to "top off."
 
I read some things lately that seemed to indicate the level 3 quick charge stations are designed to shut off at 80%. Which really makes sense when you think about it. When you can get most of your charge so fast why wait twice as long for the last little bit, and potentially hold up other people who are waiting in line for a recharge. But of course I don't know for sure. Anyone know anything about that?
 
I agree. QC will stop at ~80% whether you start at 10% or 60%. This is why a person would end up getting a lot fewer miles out of the actual QC. Very hard to pull in with less than 5%. More likely you would need to QC every 50 or 60 miles max under routine circumstances. Well if there was a QC every 5 miles then you could push it way down.
 
smkettner said:
I agree. QC will stop at ~80% whether you start at 10% or 60%. This is why a person would end up getting a lot fewer miles out of the actual QC. Very hard to pull in with less than 5%. More likely you would need to QC every 50 or 60 miles max under routine circumstances. Well if there was a QC every 5 miles then you could push it way down.

The QC could end up being an important factor for me. My commute to work is only 20 miles round trip. But I live in an apartment, and my neighborhood is not exactly upscale, so I don't see the property owners retrofitting charging stations any time soon, if at all. My boss is quite a nerd and would probably be amenable to letting me at least occasionally snake a line out the back door for some L1 charging. So I might have to mix this up with a little QC.. providing an L3 station will be built somewhere in my town (San Fernando Valley).
 
I know the brainiacs here will jump all over and explain this, but for some reason it's much faster to charge the first 80% of the battery, and the last 20% takes much longer. Why?, couldn't tell you, but I'm sure there are folks here who can answer.
 
I feel for you. Most landlords are rather stingy about such things.
Maybe once you have the car, your employer would put a 20a outlet on an existing lighting circuit in the parking lot or something that works for you.
I am hoping my employer will do something if they will not put in a regular charging dock.
 
mossyleaf said:
I know the brainiacs here will jump all over and explain this, but for some reason it's much faster to charge the first 80% of the battery, and the last 20% takes much longer. Why?, couldn't tell you, but I'm sure there are folks here who can answer.
The chemical reaction slows as the charging approaches 100%. It is the nature of all recharable batteries.
If the charge process was forced to continue at fast speed it would require continuously increasing voltage to maintain the amps at a sustained high rate. That extra voltage would cause too much heat in the battery as full charge is approched.
 
When the first guy enters the room there are 100 gals waiting to dance. Its easy for this guy to find a partner. The more guys that enter the room, the fewer partners there are and its harder for them to find a dance partner. At 80% there are now 180 people in the room and there are only 20 single gals left, the whole process begins to slow down as it is harder to find dance partners quickly when you enter the room.
 
GroundLoop said:
Also remember that once the charge stations go $pay$, you will pay the exact same price for a partial charge, or full charge.

How sure are you that's how all of them plan to charge? I saw one company was going to have a flat fee. Another wanted to sell monthly subscriptions for access to all-you-can-charge stations. Another wanted to give free charging while it showed you advertisements tempting you to use the recharge time spending money at nearby stores. It seems like there could be other business models.

To me, public charging cost is one of the big uncertainties about EV acceptance. If charging stations charge more than the energy equivalent of gasoline, drivers might be reluctant to pay, and a thousand more media pundits would pronounce EV's doomed. But if they charge less than that, I'm not sure they could recoup the cost of the chargers.
 
walterbays said:
GroundLoop said:
Also remember that once the charge stations go $pay$, you will pay the exact same price for a partial charge, or full charge.

How sure are you that's how all of them plan to charge? I saw one company was going to have a flat fee. Another wanted to sell monthly subscriptions for access to all-you-can-charge stations. Another wanted to give free charging while it showed you advertisements tempting you to use the recharge time spending money at nearby stores. It seems like there could be other business models.

Every structure you describe: You pay the same price for partial charge, or full charge. :)
 
johnr said:
I read some things lately that seemed to indicate the level 3 quick charge stations are designed to shut off at 80%. Which really makes sense when you think about it. When you can get most of your charge so fast why wait twice as long for the last little bit, and potentially hold up other people who are waiting in line for a recharge. But of course I don't know for sure. Anyone know anything about that?
Doesn't make sense to me. How does the charging station know what the charge states of the battery cells are? I suppose it could make a rough guess based on a drop in current flowing. However, the Battery Management System in the car knows much more about the charge states, so if an 80% shutoff is occurring it would make more sense to me for the BMS to shut off to prolong battery life.
 
planet4ever said:
Doesn't make sense to me. How does the charging station know what the charge states of the battery cells are? I suppose it could make a rough guess based on a drop in current flowing. However, the Battery Management System in the car knows much more about the charge states, so if an 80% shutoff is occurring it would make more sense to me for the BMS to shut off to prolong battery life.

Unlike AC L2 charging (J1772), there is data communication between the car and the DC Charger. I don't know what the protocol for that data is (yet), but it likely shares the state of charge and other details useful to the DC Charger in ending the charge.
 
GroundLoop said:
Also remember that once the charge stations go $pay$, you will pay the exact same price for a partial charge, or full charge.
Maybe not. Gas stations don't ask every customer to pay the same amount. Could be that fast charging customers will pay accoring to how many kilowatt-hours of electricity the charger dispensed...
 
tps said:
GroundLoop said:
Also remember that once the charge stations go $pay$, you will pay the exact same price for a partial charge, or full charge.
Maybe not. Gas stations don't ask every customer to pay the same amount. Could be that fast charging customers will pay accoring to how many kilowatt-hours of electricity the charger dispensed...
Or minutes on the charger taking up the space
 
tps said:
GroundLoop said:
Also remember that once the charge stations go $pay$, you will pay the exact same price for a partial charge, or full charge.
Maybe not. Gas stations don't ask every customer to pay the same amount. Could be that fast charging customers will pay accoring to how many kilowatt-hours of electricity the charger dispensed...

In many places it is illegal to resell electricity. This is why they are adopting a flat fee for using the "parking space". This way they are not charging you for the electricity, but for use of their space. They could go to a time based fee and that might work better, and be closer to fair, but some batteries will take a kWh faster than others so somebody will still complain. Unless they let charging stations charge per kWh there will always be differences.
 
wow, no comments on my little joke from last night. I was a little tired, and got a little creative. There is a little truth to the story, but the real situation is far more complicated, and the analogy breaks down pretty quickly. I was about to hit cancel because the analogy broke down as I was typing, but decided to leave it in for some light humor.
 
palmermd said:
In many places it is illegal to resell electricity. This is why they are adopting a flat fee for using the "parking space".

Initialy I think it will be flat rates.

There are utility comissions that are changing the rules to allow 3rd party companies to chrge for electricity (I think SD did that recently).
 
palmermd said:
wow, no comments on my little joke from last night. I was a little tired, and got a little creative. There is a little truth to the story, but the real situation is far more complicated, and the analogy breaks down pretty quickly. I was about to hit cancel because the analogy broke down as I was typing, but decided to leave it in for some light humor.
I thought the analogy was good, no joke. Maybe you did not mention that as the last few are running around finding a partner they will be getting hot and mad and could damage the place. So at the end they need to be let in more slowly. ;)
 
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