LeftieBiker
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 10:06 pm

WetEV wrote:
Sun Sep 29, 2019 8:12 pm
LeftieBiker wrote:
Sun Sep 29, 2019 6:36 pm
As I understand it, the 80% tapering only occurs with DCFC stations, not L-1 and L-2 stations, and the station determines when it should happen, not the onboard charger, which isn't used in DC fast charging. There is some tapering on L-1/L-2 charging, but as you found, it happens in the nineties state of charge range.

Someone correct me if I'm mistaken.
The car controls the DCFC session, not the station.

So it's the car, and not the station, that initiates ramp-down at 80% with a DCFC?
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cwerdna
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Re: Charger current drop past 80% SOC

Sun Sep 29, 2019 10:11 pm

Todd1561 wrote:
Sun Sep 29, 2019 7:49 pm
There’s no such thing as an aftermarket home charge station than can monitor actual charge level and auto shut off, correct? All my research has shown no one can do this.
There's nothing in the J1772 protocol/standard (https://openev.freshdesk.com/support/so ... -sae-j1772) for the connected vehicle to tell the EVSE its % state of charge. (DC FCing uses totally different protocols.)

That said, I hear JuiceBox can make guesstimates based upon user input and how much energy the EVSE has delivered.

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WetEV
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Re: Charger current drop past 80% SOC

Mon Sep 30, 2019 7:20 am

LeftieBiker wrote:
Sun Sep 29, 2019 10:06 pm
So it's the car, and not the station, that initiates ramp-down at 80% with a DCFC?
Yes.

Different cars have different ramp downs, which might be different with temperature and battery age. The DCQC can't be expected to be up to date on all of the different cars. So the communication between the car and the DCQC has commands the car gives to set the voltage and current limits for the DCQC. I know this is the case for CCS and Chademo. I suspect but don't know that Tesla DCQC is the same.
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Re: Charger current drop past 80% SOC

Sat Feb 22, 2020 1:16 pm

If anybody cares then tapering happens according to BMS command.
If one cell reaches maximum voltage (for example 4.12V) then current is reduced so voltage never exceeds that.
Sometimes at DC charger it happens slightly earlier, like 4.09.

Either way, if battery is very cold it will happen much earlier.
If battery is warm and new, it will accept 7kW charging rate for long, at least 90%.

Still having an Arduino that stops charging as soon as tapering starts is a good idea.
It is also possible to take different data inputs.
For example the third blue LED blinking on the dash.
When that starts...start timer for... lets say.. 1 hour and then stop charging session.
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