[Ladogaboy]

I've been trying to wrap my head around some of the economics of building out DCFC stations. Something I learned recently is that the Tesla Superchargers aren't actually large, high-power modules but rather a number of low-power (10 kW) modules chained in series.

In terms of economy, are there advantages to the smaller module model? For instance, if I wanted to build a 100 kW DCFC tower, would it be cheaper to use ten 10 kW modules or four 25 kW modules? Would there be additional costs or complications?

 

[saghost]

I've been trying to wrap my head around some of the economics of building out DCFC stations. Something I learned recently is that the Tesla Superchargers aren't actually large, high-power modules but rather a number of low-power (10 kW) modules chained in series.

In terms of economy, are there advantages to the smaller module model? For instance, if I wanted to build a 100 kW DCFC tower, would it be cheaper to use ten 10 kW modules or four 25 kW modules? Would there be additional costs or complications?

I'm not sure if there's an inherent advantage to the smaller modules on a clean sheet. I think they all use very similar high power transistors to manage the power, so I'd suspect the cost would scale fairly consistently.

Tesla derives two advantages from the modular approach for their specific case.

First, the modules they use in the Superchargers are the same as the onboard chargers they install in every car, so they presumably get big economy of scale cost benefits since they are building hundreds of thousands of them per year now.

The second benefit is granularity in charging. The electronics are connected to a pair of stalls, and by having 12 discrete modules, it has the ability to connect some to one outlet and some to the other, letting it max out the first car to plug in and give everything that's left to the second car, so they get twice as many plugs for a given input power and almost the same investment cost. Charging is slower for the second half of the cars if the first group of cars are low on charge, but it's much better than being left waiting for the other session to finish.

 

[Norton]

10 kW modules. That's the total Power, but no mention of open DC voltage or amperage curve.
10 x 40 VDC modules in series would have an output of 400 VDC.
4 x 125 VDC modules would be 500 VDC open terminal voltage.
The current is what is controlled to maintain the kW amount during the charge process.

I suspect it is very complicated to 'One-off' a home brew DCFC.

Besides, what home are you going to plug this 416 Amp / 240 VAC device into?
I'm pretty sure DCFC units require 3 phase power.

Edit: I got to take a look inside an Efacec 50 kW DCFC unit.
These are as big as a refrigerator, but there is lots of empty space on the inside.
Down at the bottom is a very big and heavy transformer. Big wires too!

 

[saghost]

10 kW modules. That's the total Power, but no mention of open DC voltage or amperage curve.
10 x 40 VDC modules in series would have an output of 400 VDC.
4 x 125 VDC modules would be 500 VDC open terminal voltage.
The current is what is controlled to maintain the kW amount during the charge process.

I suspect it is very complicated to 'One-off' a home brew DCFC.

Besides, what home are you going to plug this 416 Amp / 240 VAC device into?
I'm pretty sure DCFC units require 3 phase power.

Edit: I got to take a look inside an Efacec 50 kW DCFC unit.
These are as big as a refrigerator, but there is lots of empty space on the inside.
Down at the bottom is a very big and heavy transformer. Big wires too!

Tesla's approach is the other way - 12 ~10-15 kW capable modules connected in parallel, each outputting up to 400 V DC as required.

 

[Ladogaboy]

I'm not really considering this for home use. This is more to inform myself about the logistics of building out high-speed public charging infrastructure. As saghost mentioned, Tesla benefits from an economy of scale, but to build out the Supercharger network as effectively as they have indicates that it is a viable, economic strategy.

 

[Ladogaboy]

Tesla's approach is the other way - 12 ~10-15 kW capable modules connected in parallel, each outputting up to 400 V DC as required.

Ah, so they run it parallel. I guess that makes more sense. I thought the output was higher than 400 VDC. I guess not.

 

[saghost]

Ah, so they run it parallel. I guess that makes more sense. I thought the output was higher than 400 VDC. I guess not.

I'm not sure what the maximum capacity is. The big battery Teslas are 96 cells in series, ~400V nominal, and I think they max out at around 430V at full charge?

Given how the rest of the industry rates their DCFC units, I wouldn't be surprised if the SpC can go to 500V, but there's never been a reason for them to, so far.

 

[freshcut]

multiple modules does seem to make a lot more sense since if one module fails it's unlikely to bring the whole system down where if one module were used, it would render that charging station dead. Another way to possibly look at it is how supercomputers are built. They don't use one super fast processor but rather dozens or hundreds all working together. From a final cost standpoint, it's not cheap for either, but from a redundancy standpoint a failure of one or two smaller components is unlikely to impact the entire system and cause a total failure.

 

[Ladogaboy]

I'm not sure what the maximum capacity is. The big battery Teslas are 96 cells in series, ~400V nominal, and I think they max out at around 430V at full charge?

Given how the rest of the industry rates their DCFC units, I wouldn't be surprised if the SpC can go to 500V, but there's never been a reason for them to, so far.

Yeah. I'm not well versed in the exact charging/pack voltage details for the Tesla. Maybe an owner could chime in. I just know that I've been told they can take advantage of the voltage beyond 400 VDC.

multiple modules does seem to make a lot more sense since if one module fails it's unlikely to bring the whole system down where if one module were used, it would render that charging station dead. Another way to possibly look at it is how supercomputers are built. They don't use one super fast processor but rather dozens or hundreds all working together. From a final cost standpoint, it's not cheap for either, but from a redundancy standpoint a failure of one or two smaller components is unlikely to impact the entire system and cause a total failure.

That is true, unless one module going down could trip the entire system. Still, I could envision a charging location with four individual 24 kW DCFC that could either charge one car at 96 kW, two cars at 48 kW, or four cars at 24 kW. Especially with a program for prioritizing, I could see how that would be a much better model than the current two 50 kW chargers that don't interlink.

 

[saghost]

That is true, unless one module going down could trip the entire system. Still, I could envision a charging location with four individual 24 kW DCFC that could either charge one car at 96 kW, two cars at 48 kW, or four cars at 24 kW. Especially with a program for prioritizing, I could see how that would be a much better model than the current two 50 kW chargers that don't interlink.

What makes you think the Typical 50 kW CCS/50 kW CHAdeMO has two chargers?

I was under the impression that those had a single 50 kW DC module, which can be connected to either cord and speak to the car in either protocol. That's why you can never use both at the same time, I thought.

 

[DonC]

I don't think the equipment cost is a big deal. The major cost is getting that much power to the charging station. After construction the big driver for operating costs is demand charges which you can mitigate with battery storage. Locating the chargers would be 1000X easier for electrical utilities.

I'm also under the impression that the CCS/CHAdeMO chargers have only one module.

 

[Chris TX]

If you really wanted, you could use the new Gen2 chargers from Tesla that produce 18kW each. Just a small stack of six will get you ~100kW, depending on your input voltage. Keep in mind, you would need ~500A on single phase to run it. If you take it to 208VAC three phase, it drops down to ~90kW, but you need only 200A service with a 480VAC transformer. Six chargers would split nicely with 3phase, as well with two chargers per phase.

You'll need a 000 gauge busbar to connect the DC side, and the water cooling can be done outside the garage. In the winter, you can even use it to heat the house.

 

[Ladogaboy]

What makes you think the Typical 50 kW CCS/50 kW CHAdeMO has two chargers?

I was under the impression that those had a single 50 kW DC module, which can be connected to either cord and speak to the car in either protocol. That's why you can never use both at the same time, I thought.

I'm also under the impression that the CCS/CHAdeMO chargers have only one module.

Most of the sites (at least EVgo) have two 50 kW chargers each with CCS/CHAdeMO. There is some variance, where some locations only have one 50 kW charger with CCS/CHAdeMO, and some have two 50 kW chargers, one with CCS/CHAdeMO and the other with only CHAdeMO.

 

[saghost]

Most of the sites (at least EVgo) have two 50 kW chargers each with CCS/CHAdeMO. There is some variance, where some locations only have one 50 kW charger with CCS/CHAdeMO, and some have two 50 kW chargers, one with CCS/CHAdeMO and the other with only CHAdeMO.

Okay. Most of the sites out here are a single CCS/CHAdeMO, though I have seen A CCS/CHAdeMO with a CHAdeMO - and the one right near work is a CCS only, something I really hadn't seen otherwise.

 

[Ladogaboy]

Okay. Most of the sites out here are a single CCS/CHAdeMO, though I have seen A CCS/CHAdeMO with a CHAdeMO - and the one right near work is a CCS only, something I really hadn't seen otherwise.

Yes, for those stations, they are a single 50 kW charger. My understanding is ChargePoint's new Express line of chargers are supposed to coordinate between other chargers onsite, and the basic version will have two ~31 kW modules. I've yet to see how they divide power, but the 50 kW EVgo stations will not allow two active charges at the same time.