rainbow
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Reduce current absorption during EV charging

Wed Oct 07, 2020 2:22 pm

Hi, I'm a newbie about EVs and I'm here to ask for a clarification.
After reading some docs about EVs, I learned that there are 4 different charging modes, where each of them specifies voltage and current values during EV charging (so, indirectly, the absorbed power).

For example, I read that in my country, during a slow charge, the EV is recharged by a single-phase supply (230 V) and it will absorb, at maximum, 16 A (so about 3.7 kW).
"16 A" corresponds to the maximum current rating of an household, so I guess that, during EV charging, it's possible to reduce the current which the EV absorbs, so that it is also possible to use, at the same time, some other electric equipment (such as TVs, appliances, ...) without causing an electric overload.

Is it right?
If yes, how the current, during the charging phase, is reduced? "Manually" or is it done by a specific device?

Is there anyone who could clarify me this? Thank You!

LeftieBiker
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Re: Reduce current absorption during EV charging

Wed Oct 07, 2020 3:22 pm

The device that feeds the car's onboard charger current is called an "EVSE" (which stands for something like "Electric Vehicle Service Equipment") and this is where you have control over the amount of current the car draws. In North America we have the option of 120 volt, 12 amp "trickle charging," but in the EU and other places with high voltage AC only, you need to either get an EVSE with selectable current levels, or one with a single fixed current level that meets your needs. The Leaf will, if I remember correctly, accept charge current as low as 8 amps - possibly 6 amps. Once we verify that, you can look for an EVSE that provides the car with that amount of amperage.
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goldbrick
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Re: Reduce current absorption during EV charging

Wed Oct 07, 2020 4:58 pm

The current is set at the beginning of a charging session by communication between the car and the EVSE mentioned above. There is a specified protocol used to set the amount of current for the charging session. I don't think the voltage is negotiated since that is fixed.

Different Leaf's can have different on-board chargers. In the US, they are either 6.6kW or 3.x kW. The 6.6kW charger option will charge at up to 27.5A if the EVSE supports that.

You need to figure out how much current the house charging circuit can supply then find an EVSE that will allow you to set the charging current to not exceed that amount. With that in place, the EVSE will limit the charging current to what the house can safely provide. The most charging current you can use will be determined by the lowest of 1) the house circuit's capacity 2) the EVSE's capacity and 3) the Leaf's capacity (27.5A).

The EVSE is normally the device that determines the charging current and should be set to limit the current to what the house can provide (probably 16A in your case).

LeftieBiker
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Re: Reduce current absorption during EV charging

Wed Oct 07, 2020 5:26 pm

The EVSE is normally the device that determines the charging current and should be set to limit the current to what the house can provide (probably 16A in your case).

I think the OP is saying that their entire household has a 16A limit, in which case 6-8A would be more appropriate. Or maybe they just meant that 16A is a lot of current...
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rainbow
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Re: Reduce current absorption during EV charging

Tue Oct 13, 2020 3:05 am

Thanks to all of you, very useful!
So, now, I know that it's possible to recharge an EV with currents lower than the maximum value defined by a particular "Charging Mode".

Now, I have a couple of technical questions:

1) By reading this Wikipedia page about Type 1 connector (SAE J1772), I learned that there's a relationship between the "Duty Cycle" of the control signal and the maximum current value allowed by the connector.
At that link, there's a the table entitled "PWM duty cycle indicating ampere capacity", which shows some current values, each of them associated to a corresponding "Duty Cycle" of the control signal.
Only six current values (6A, 9.6A, 15A, 18A, 24A, 30A) are shown in the table, but I don't think they're the only ones, because it's easy to find on the market adjustable EVSEs which allow to select maximum current values different from these (e.g., 8A, 10A, 13A, 16A).
Am I right?
Moreover (silly question), does the connector technical spec allow to choose (as the maximum current value to recharge the EV) only a value included in a specific limited set of possible maximum current values?
Or, does the normative allow to choose whichever maximum current value to recharge the EV, so that it will be limited to the minimum between 1) the selected value on the adjustable EVSE and 2) the maximum current value which the power mains can deliver?

2) Type 1 Wikipedia page says that:
The European versions were equipped with a SAE J1772-2009 inlet as well until the automotive industry settled on the IEC Type 2 “Mennekes” connector as the standard inlet — since all IEC connectors use the same SAE J1772 signaling protocol the car manufacturers are selling cars with either a SAE J1772-2009 inlet or an IEC Type 2 inlet depending on the market.
The bold part says that all IEC connectors (so, even Type 2) use the same "signaling protocol" as the one used by the Type 1 connector (also called SAE J1772), so I guess that even Type 2 uses the same "duty cycle-max current" relationship described above, for Type 1 connector.
Is it right?

LeftieBiker
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Re: Reduce current absorption during EV charging

Tue Oct 13, 2020 4:41 am

If I understand you correctly, the amperage is determined solely by the control unit of the EVSE, not by the J-1772 plug, so AFAIK it can be anything in the specified range as determined by the EVSE control unit. As for whether the J-1772 protocol is identical to that used in European versions of the EVSE, my guess - and it's only a guess - is "yes."
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Nubo
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Re: Reduce current absorption during EV charging

Tue Oct 13, 2020 8:48 am

rainbow wrote:
Tue Oct 13, 2020 3:05 am
Thanks to all of you, very useful!
So, now, I know that it's possible to recharge an EV with currents lower than the maximum value defined by a particular "Charging Mode".

Now, I have a couple of technical questions:

1) By reading this Wikipedia page about Type 1 connector (SAE J1772), I learned that there's a relationship between the "Duty Cycle" of the control signal and the maximum current value allowed by the connector.
At that link, there's a the table entitled "PWM duty cycle indicating ampere capacity", which shows some current values, each of them associated to a corresponding "Duty Cycle" of the control signal.
Only six current values (6A, 9.6A, 15A, 18A, 24A, 30A) are shown in the table, but I don't think they're the only ones, because it's easy to find on the market adjustable EVSEs which allow to select maximum current values different from these (e.g., 8A, 10A, 13A, 16A).
Am I right?
Moreover (silly question), does the connector technical spec allow to choose (as the maximum current value to recharge the EV) only a value included in a specific limited set of possible maximum current values?
Or, does the normative allow to choose whichever maximum current value to recharge the EV, so that it will be limited to the minimum between 1) the selected value on the adjustable EVSE and 2) the maximum current value which the power mains can deliver?

2) Type 1 Wikipedia page says that:
The European versions were equipped with a SAE J1772-2009 inlet as well until the automotive industry settled on the IEC Type 2 “Mennekes” connector as the standard inlet — since all IEC connectors use the same SAE J1772 signaling protocol the car manufacturers are selling cars with either a SAE J1772-2009 inlet or an IEC Type 2 inlet depending on the market.
The bold part says that all IEC connectors (so, even Type 2) use the same "signaling protocol" as the one used by the Type 1 connector (also called SAE J1772), so I guess that even Type 2 uses the same "duty cycle-max current" relationship described above, for Type 1 connector.
Is it right?
Found this chart, fwiw. I can't vouch for it. Source: http://myimiev.com/forum/viewtopic.php?t=1497&start=110 Image
I noticed you're still working with polymers.

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