DC Charging for the Roadster

[richkae]

Assume that someone could build such a box, that cleanly inserts into the car ( I assume between the battery and the PEM ) and provides you with a CHAdeMO plug ( that lives under the trunklid ).
Also assume this box provides you a maximum of 40kW charge rates from a CHAdeMO plug and you could get it built and installed for $5000.

How many people would want one?
What about if it was $10000?

 

[stopcrazypp]

The PEM has connectors to the ESS as well to the charger (and AC-Motor). The cables to the battery can handle the short term load of 700-800A (225kW) and continues load of 40kW. It will work.

To make it more clear, I'm not talking about "connectors". I'm talking about a "contactor", which is basically a switch that makes it so you don't have any live current on the DC pins until the DC connection is established. It is required for any type of DC charging, but is not necessarily present in every single BEV (esp. one you can connect to on the outside)
http://en.wikipedia.org/wiki/Contactor

In particular, you need one that can handle ~50kW of power to use CHAdeMO at near full power. Given the Roadster has a 16.8kW onboard charger, it may have one that can handle at least ~20kW of power, but I don't know how much higher it may go or if it even exists and can be connected to. And I don't know if there are contactors between the PEM and the batteries, what kind of power rating they have, and if you can access them.

I know you can probably source a CHAdeMO socket for fairly cheap (and the other electronics to do the hand shaking), but I'm not sure how much such a contactor will cost.

 

[Eberhard]

Assume that someone could build such a box, that cleanly inserts into the car ( I assume between the battery and the PEM ) and provides you with a CHAdeMO plug ( that lives under the trunklid ).
Also assume this box provides you a maximum of 40kW charge rates from a CHAdeMO plug and you could get it built and installed for $5000.

How many people would want one?
What about if it was $10000?

If this would include the CHAdeMO charger - thats great. But only the socket? should not be more expensive then the HPC or UMC.

 

[Norbert]

That's not particularly useful because it doesn't tell us the impact of charging faster, or how much life you gain (or lose) by charging at a slower rate. Nor does it tell us the "optimal" charging speed ("0.8c or less" is different than saying "0.8C" period). And it doesn't provide data to back that claim.

It also seems to refer to a "typical consumer Li-ion battery" in general.

 

[hcsharp]

To make it more clear, I'm not talking about "connectors". I'm talking about a "contactor", which is basically a switch that makes it so you don't have any live current on the DC pins until the DC connection is established. It is required for any type of DC charging, but is not necessarily present in every single BEV (esp. one you can connect to on the outside)
http://en.wikipedia.org/wiki/Contactor
...

You might need much more than just access to the contactor. You have to work with the software and hardware. For DC charging you would pretty much have to charge the cells in series, which means that unless the firmware was upgraded to communicate with our new DC charger, we would have no way to know if we were overcharging (above 4.15V) one of the bricks. If you were certain that your cells were already well balanced, you might be able to get away with charging to about 80% capacity to be safe.

If all we had was access to the contactor and lucky enough to get a firmware upgrade from Tesla, could we still do this? The only thing we know for sure about the hardware is that it can handle charging in series for very brief periods at rates up to 40kW. That's what regen does. You can't assume that since it can discharge at 200kW that the same circuit can charge at 40 or 50kW for extended periods like 1 or 2 hrs.

 

[GSP]

The high voltage contactors would have to be inside the ESS to allow disconnecting the ESS terminals for safe transport, vehicle assembly, and servicing. I think there is a basic ESS schematic posted elsewhere on this site that showers the contactors.

The cables from the ESS to PEM could be replaced with a three-way cable (probably $1000 from a good outfit such as MTG Moltec). This cable would be connected to a separate box with contactors for the ChadeMo connector. This box with contactors will be required to keep high voltage disconnected from the ChadeMo connector except when charging. Contactors can be purchased from Panasonic, GigaVac, KiloVac, or others. The box will also need a microprocessor with mutiple CAN transceivers to communicate with the ChadeMo charger and one or more vehicle CAN networks. Count on at least another $1000 for the box.

The box will need software. A roadster and a ChadeMo charger will be required for development and testing. This will not be free. Changes to the Roadster's firmware may also be required. That could be REALLY expensive if reverse engineering if required.

This project sounds like a worthwhile follow on to the J1772 conversion project and the OVMS project.

GSP