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Discussion Starter #1 (Edited)
Edited for correction

Wanted to know why an onboard charger was required. It's now been answered as below.

Home charging is always AC.

All EVs have an onboard charger which takes AC (usually provided via a Type 2 plug) and converts that to DC internally to charge the battery. Most models can only take a single-phase 7kW AC charge (occasionally less), but some take 3-phase AC at higher power levels including 22kW and more. Most home chargers can't deliver more than 7kW as most UK homes don't have 3-phase supplies.

Many EVs can also take a DC connection, direct to the battery, for DC Rapid Charging which is provided by public chargers via CCS or CHaDeMo connectors. In this case it's the public charger's job to convert the mains AC to DC at high power levels, and manage the charging.
Public charge points for EV's use direct current (DC) and AC (alternating current).

EV batteries use DC.

Outlets such as those in homes use AC, so the car has to have an onboard AC to DC converter/charger box. These are often less powerful such as 22kw, whereas public chargers can connect direct to battery, bypassing onboard charger and then charging faster.
 

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Public charge points for EV's use direct current (DC), rather than AC (alternating current).
That's not true. High power rapids (Chademo and CCS) are DC, others rapids may be 43 kW AC for cars that use that. Most other public points will be 7 or 3.5 kW AC which are the same as home outlets and those use the car's on-board charger. As you say, the latter will have a power limit.
 

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Just wanted to clarify if the following is correct:

Public charge points for EV's use direct current (DC), rather than AC (alternating current). EV batteries use DC.
However, outlets, such as those in homes use AC, so the car has to have an onboard AC to DC converter/charger box.

The onboard charger on all BEVs and plug in chargers had to provide an AC to DC conversion as you state but had other important functions such as providing the correct voltage and controlling the charging rate. The AC Input rating of the onboard charger could be anything from 2.5kW to 43kW depending on the model of car.

But onboard chargers often can only convert up to 11 or 7kw.

Let me know if I got anything wrong, thanks.

Literally everything in this post is incorrect.

Vast majority of public charge points provide single phase or three phase AC.

SOME public charge points, normally known as Rapid chargers, provide DC.
 

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However, outlets, such as those in homes use AC, so the car has to have an onboard AC to DC converter/charger box.

But onboard chargers often can only convert up to 11 or 7kw.
Does it matter if the onboard charger can only convert at a rate of 11 or 7 (or even 3.6) kW - if you plug in when you get home in the evening, you will have a fully charged battery by the next morning.

There are two 'modes' of charging - destination charging when the car is charging while you are doing something else, and en-route charging when you are waiting for the car to charge so you can get on with your journey.

For destination charging, providing you can get enough charge for your next journey while you are at the destination, the actual charging rate does not matter.

For en-route charging, you would like to charge as quickly as possible so that you can be on your way, so the 'Rapid' chargers that feed DC direct to your battery are the ones to go for.
 

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AC from the mains has to be converted to the correct volts ( every car is different depending on battery configuration AND state of charge! Plus it has to be DC
 

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Discussion Starter #7
AC from the mains has to be converted to the correct volts ( every car is different depending on battery configuration AND state of charge! Plus it has to be DC
So, not literally everything in my initial post was incorrect then?

"However, outlets, such as those in homes use AC, so the car has to have an onboard AC to DC converter/charger box."
 

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So, not literally everything in my initial post was incorrect then?

"However, outlets, such as those in homes use AC, so the car has to have an onboard AC to DC converter/charger box."
Your original post was pretty much correct, but people have jumped on it because of the suggestion that public charging is always DC, when you can obviously get public AC chargers as well as DC. Home charging is always AC.

All EVs have an onboard charger which takes AC (usually provided via a Type 2 plug) and converts that to DC internally to charge the battery. Most models can only take a single-phase 7kW AC charge (occasionally less), but some take 3-phase AC at higher power levels including 22kW and more. Most home chargers can't deliver more than 7kW as most UK homes don't have 3-phase supplies.

Many EVs can also take a DC connection, direct to the battery, for DC Rapid Charging which is provided by public chargers via CCS or CHaDeMo connectors. In this case it's the public charger's job to convert the mains AC to DC at high power levels, and manage the charging.
 

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Your original post was pretty much correct, but people have jumped on it because of the suggestion that public charging is always DC, when you can obviously get public AC chargers as well as DC. Home charging is always AC.

All EVs have an onboard charger which takes AC (usually provided via a Type 2 plug) and converts that to DC internally to charge the battery. Most models can only take a single-phase 7kW AC charge (occasionally less), but some take 3-phase AC at higher power levels including 22kW and more. Most home chargers can't deliver more than 7kW as most UK homes don't have 3-phase supplies.

Many EVs can also take a DC connection, direct to the battery, for DC Rapid Charging which is provided by public chargers via CCS or CHaDeMo connectors. In this case it's the public charger's job to convert the mains AC to DC at high power levels, and manage the charging.
As someone who cannot us rapids anyway, I am slightly nervous about the notion that a public rapid charger which may not be too well maintained would be in control of what happens to my battery. I thought that all the tapering of charge rates and power levels was controlled by the car to protect the battery. Is that wrong?
 

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Discussion Starter #11
As someone who cannot us rapids anyway, I am slightly nervous about the notion that a public rapid charger which may not be too well maintained would be in control of what happens to my battery. I thought that all the tapering of charge rates and power levels was controlled by the car to protect the battery. Is that wrong?
Yeah. You'd expect there would be a fuse or voltage monitor between the charger and the battery - either on the charger itself and/or the car to disconnect if it falls outside of bounds.
 

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Wanted to know why an onboard charger was required.
It is not 'required' but if you didn't have one you'd need a DC charger at home (assuming you wanted to charge at home).

The OBC is an AC->DC converter to make conventional mains suitable to charge a DC battery. There is no particular reason why that converter needs to live in your car rather than on your garage wall, but it is just the way this EV thing has evolved, with the only electrical supplies originally being your house, so it made sense to carry that converter around with the car in case you stopped somewhere else with AC only supply.

Personally, I think that is the way this will all go, and OBCs will be deleted for cost and weight benefits, but at the moment there is no industry/market for that.
 

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It is not 'required' but if you didn't have one you'd need a DC charger at home (assuming you wanted to charge at home).

The OBC is an AC->DC converter to make conventional mains suitable to charge a DC battery. There is no particular reason why that converter needs to live in your car rather than on your garage wall, but it is just the way this EV thing has evolved, with the only electrical supplies originally being your house, so it made sense to carry that converter around with the car in case you stopped somewhere else with AC only supply.

Personally, I think that is the way this will all go, and OBCs will be deleted for cost and weight benefits, but at the moment there is no industry/market for that.
I got a great idea. We could get the manufacturers to not fit any seats / seatbelts/ airbags for passengets. Just think of the weight and cost saving. The idea being that g&d forbid anyone would need them, just fit your own from your previous car. Same with wheels, just transfer them over. SatNavs arn't needed. Windows that open are an anachronism, ditch them. Let's keep going and get cars stripped down to what a buyer really needs!
 

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I see the point @donald is making that long term (at least 5 years) AC charging might disappear or be a cost option.

It is far harder and expensive to do V2G with AC, so long term homes could have low power DC charging due to V2G requirements. The units are already getting cheaper and smaller as we see with the current trial.
 

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It is not 'required' but if you didn't have one you'd need a DC charger at home (assuming you wanted to charge at home).

The OBC is an AC->DC converter to make conventional mains suitable to charge a DC battery. There is no particular reason why that converter needs to live in your car rather than on your garage wall, but it is just the way this EV thing has evolved, with the only electrical supplies originally being your house, so it made sense to carry that converter around with the car in case you stopped somewhere else with AC only supply.

Personally, I think that is the way this will all go, and OBCs will be deleted for cost and weight benefits, but at the moment there is no industry/market for that.
Most EVs can regenerate many kWs from the AC motor, and the supply to houses and everywhere else is AC. If the car has effectively a four quadrant controller, and it works, why add the expense and unreliability of a public DC charger.. once the Renault patent runs out.
 

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Most EVs can regenerate many kWs from the AC motor, and the supply to houses and everywhere else is AC. If the car has effectively a four quadrant controller, and it works, why add the expense and unreliability of a public DC charger.. once the Renault patent runs out.
Power quality.

To add in the additional features to make the supply free of transients takes up a lot of physical bulk in the form of large capacitors and inductors, which is space and weight a regular car can't afford.

Renault does it by using its particular motor design to double up as the inductors. Not possible with any other current EV.

That's assuming the voltages are compatible in the first place, which will be even more bulk mass and cost if not.

A home charger would still be 7 kW or so, just DC to the car.
 

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Sorry to disagree with suggestion that home DC chargers will be the norm and onboard chargers will be dumped.

Already there are issues with comms compatibility between EVSEs and BEVs. Imagine the long winded process in terms of certification and actual compatibility, DC chargers to any BEV that would happen if DC home charging was to be the norm.

Not only that, but the acceptance threshold for adoption of BEVs would increase. Help us all if OLEV got involved in assigning minimum acceptable technical standards for their "approved" DC home chargers.

Thoroughly bad idea.

Safety: 400V DC trailing flexible cables subject to random domestic maintenance approach. Sorry, did I say thoroughly bad idea.
 

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Sorry to disagree with suggestion that home DC chargers will be the norm and onboard chargers will be dumped.

Already there are issues with comms compatibility between EVSEs and BEVs. Imagine the long winded process in terms of certification and actual compatibility, DC chargers to any BEV that would happen if DC home charging was to be the norm.

Not only that, but the acceptance threshold for adoption of BEVs would increase. Help us all if OLEV got involved in assigning minimum acceptable technical standards for their "approved" DC home chargers.

Thoroughly bad idea.

Safety: 400V DC trailing flexible cables subject to random domestic maintenance approach. Sorry, did I say thoroughly bad idea.
Maybe you have missed that 1000 homes in UK are getting DC chargers for V2G? They are being made by Indra and I am sure @Mike Schooling will confirm they are perfectly "safe"

 

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Yes, did certainly register before I made that post.

I have every confidence that Indra will manage quality of supply, installation, maintenance and possibly operation over the period of a TRIAL.

Not the same as mass market IMHO.

Any views from Indra themselves on what would be required long term?

Just conscious that at 400V (800V for some cars on the way) we have crossed over some basic physiological safety barriers. Certainly with Public DC charging, we expect that a level of maintenance is carried out by competent persons.
 
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