openinverter forum

Hi everybody and thanks for this awesome open source & hardware project!

Do I understand correctly, that CCS2 allows to drive fast charging (with those external charging stations) for essentially any LiFePo4 battery packs, as long as one has an CCS2 port and the FOCCCI board continuously relays the cell measurements from the BMS through the communication line to the charging station? For example, if one manages to grab the cell measurements from a Renault Twizy BMS then one could fast charge its 6kWh LFP battery with DC from the charging station? Shouldn't this reduce charging time quite a bit, say very roughly ~12 min at 30kW?

In principle, yes. Provided the battery and cooling system can handle it. With the Twizzy, the main obstacle will be the 48V system, since DC charging stations typically start at 150V to 200V.

Thanks!! Indeed, onboard battery seems between 40-60V depending on charge -- very sad ((
Seems CHAdeMO instead of CCS2 won't help there either?
Found this EV schema: https://www.twizy-forum.de/attachment/41852
Seems easier then to build a separate range extender high voltage battery with BMS, FOCCCI, and CCS2 port to get DC fast charging from the stations.
The range extender then needs separate DC-DC converter to hook into the EVs battery recuperation, or is there something easier that I'm missing?
Guess any cheap >200V battery system, with high kWh, C-rating, and accessible BMS, would be a good basis for this endeavor, though I was hoping for fast charging with little extra stuff.

I have a similar problem with my conversion I am planning.
It is likely a ca 100 volt system but when I see the number of CCS chargers on the routes I want to drive with the car I would like to have the option: Not because I want the speed of charging but just to have the freedom of choice.

I could do a 22 KW AC system fairly easily but I did a trip to Buxtehude a few weeks back and a lot of the AC chargers there only put out 4-9 KW for my Enyaq which strengthened my desire for some sort of a fast charge option...

I saw a video about how the Rivian truck actually changes the batteries from parallel to serial to up the voltage for fast charging and then switches back to increase capacity.

I would have fairly easy access to the batteries so I was wondering about the feasibility of doing that as well...

One other reason is I would like to take part in the e4 festival on the Hockenheimring and the standard chargers you have use are CCS :;-)

DVD3500 wrote: ↑Mon Apr 27, 2026 9:39 am I saw a video about how the Rivian truck actually changes the batteries from parallel to serial to up the voltage for fast charging and then switches back to increase capacity.

I would have fairly easy access to the batteries so I was wondering about the feasibility of doing that as well...

That's actually the GM EV trucks (Silverado, Hummer, Sierra, and Escalade), not Rivian. They are able to do so because they are essentially using two 400V packs stacked on top of each other. So they run in parallel while driving, and series when charging on an 800V capable station.

Oh right, I got that confused with the Cannonball run Rivian... I am getting old ...

DVD3500 wrote: ↑Tue Apr 28, 2026 12:45 pm Oh right, I got that confused with the Cannonball run Rivian... I am getting old ...

In fairness to you, there were videos about both, on the same channel, released fairly close to each other.

Mathieu Rech did the same on his Landcruiser conversion. It is also a 120V system and he used a funky relay matrix to switch between 2 parallel 120V pack and series 120V packs. Worked a treat.

A list of different charger types, with their minimum supported voltage, is available in the wiki: https://openinverter.org/wiki/CCS_Fast_ ... (Overview)
The most critical is the Tesla Supercharger, which rejected requests below 230V.

The CCS min V list is very interesting, thanks!
Unfortunately, the lowest is 50V and that somehow suggests that it may fail in the pre-charge phase to lower the voltage to an empty battery of a 48V system like a Twizy

Indeed, the reconfigurable battery is interesting and I played with that thought some more.
Original is 14S, I believe. But to be above >>200V in empty state, and having a number of cells that is a multiple of 14, one would need the cells in 6 modules that can be reconfigured from 84S (charging) to 6P14S (driving), that is substantially more complicated than switching 2P... to series and back.
First, that is a lot of cells to wire up. With LFP, the smallest main stream seems 20Ah then 50Ah. So the block would be quite big and heavy.
Second, doing the switching "safely" when everything is sealed in a waterproof housing is challenging for electronics and mechanics.
To swap, one would first need to safely disconnect the 6 modules (busbars or wires are huge).
Next the modules may have slightly different voltages, so just switching 6P14S<->84S could result in strong current.
Think one would need use resistors to gradually equalize the modules' voltages.
Finally, one would connect the 6 modules in series and charge.
After charging, the three steps would need to be done in reverse.
I believe that the electro-mechanical components to implement this safely would be super expensive (and need lots of space), especially when one wants this for 6 modules (
[ Though it seems easier to have a separate HV range extender battery with CCS and board system with 48V, then one would need a DC-DC converter that allows for HUGE current, as driving can easily draw up to 15kW already in case of the Twizy. ]

My conclusion, the CCS station network, build partially with taxpayer's money, are yet another win for the lobby of big car concerns that force everybody to buy a new, extremely expensive, EV that has a HV battery that the "customer" isn't even allowed to repair.
Nobody talks about "right to repair" for an EV, and lawmakers are only interested in "right to repair" for phones.