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Discussion Starter #1
Hello,

I am studying the design of DC fast chargers.

I learned some information about their varieties and the approximate principle of operation (Vienna Rect. - LLC DC/DC - Output).



Usually, after Vienna Rectifier, you can get a maximum voltage of about 840VDC, and then lower it to the desired level using a DC/DC converter.

Most electric vehicle models have battery voltages in the range of 345 - 480VDC.

The exception is the Porsche Taycan, which has an 800V battery.

It is charged by CCS, which can reach 920VDC.

As I understand it, usually the charging modules that make up the fast chargers give out 250-750VDC.
Further, they are already connected in parallel, for a set of high power.

I wondered how the CCS outputs such a high voltage (Up to 920VDC), if usually the modules produce up to 750VDC (which is enough for CHAdeMO).

Are they using other DC/DC designs (Buck-Boost) or simply combining serial and parallel connection of charging modules to increase the voltage?

Or is this voltage the sum of DC (up to 750V) and AC on the CCS plug?


Thank you!
 

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The rapid charger will always match the battery voltage (roughly speaking), so I don’t know where you are getting that CCS will always out our these voltages.
 

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Thanks for the answer!


Perhaps I did not quite correctly put the question.

The charging modules, the diagram of which is shown in the picture, output a range of 250 - 750V, which is suitable for most models of electric vehicles.
Yes, battery voltage will vary depending on the charge level.

The maximum voltage that the CCS can give - 920V, is closest to this voltage of the Porsche Taycan (800V - charged battery).
The CCS output will be limited by the maximum battery voltage of the electric vehicle (depending on the model).

The question is, how will the modules deliver such a high voltage to it if they have an output of up to 750V.

I did not find any special information on this, but my main assumption is that the charging station connects several such modules in series to give more than 750V to the output of the CCS).
 

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You could change the windings ratio on the transformer to give a higher voltage output, less turns on the primary, more on the secondary with suitably rated rectifiers and capacitors. High power switch mode supplies aren't my speciality but I'm sure there are many ways that it can be done, the secret to all of these things seems to be rapid switching of the FET's and Diodes so they don't absorb too much energy as they switch.
 

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The AC pins are not used. In fact, a typical ccs2 DC connector does not have them:
133432


I'm sure that the internal topology of the charger will be a Buck-Boost converter.

150-175kW chargers can not necessarily provide the full voltage, hence why the taycan has an on-board boost converter (50kW standard, 150kW cost option). 350kW chargers do offer the full voltage range, but typically limited to 500A at lower voltages (and so represent a 200kW charger max for Tesla model 3). The application diagram you showed above is probably for a 175kW.
 

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The design shown uses 1200v rated parts, and sets a limit of 840v based on that. If you want 1000v DC, then clearly you select parts with a higher voltage rating and build the power supply with those instead.
 

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Discussion Starter #7
Many thanks to all for the suggested answers! Indeed, I believed that CCS is a COMBO of AC and DC (inside the machine, the AC is rectified from the indoor unit and enters the battery).
 
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