EV fast-charging comes to condos and apartments(arstechnica.com)
arstechnica.com
EV fast-charging comes to condos and apartments
https://arstechnica.com/cars/2024/04/ev-fast-charging-comes-to-condos-and-apartments/
20 comments
It sounds like you almost have enough numbers to calculate the ball-park efficiency.
Grid -> condo battery ~85% (basically an L2 charger)
Condo battery -> L3 charger let's say ~96%[0] because it's a high discharge rate
L3 charger -> car ~90%
It's simple math now: 0.85 * 0.96 * 0.90 = ~74% end-to-end efficiency.
[0] https://www.researchgate.net/figure/Energy-efficiency-map-of...
Grid -> condo battery ~85% (basically an L2 charger)
Condo battery -> L3 charger let's say ~96%[0] because it's a high discharge rate
L3 charger -> car ~90%
It's simple math now: 0.85 * 0.96 * 0.90 = ~74% end-to-end efficiency.
[0] https://www.researchgate.net/figure/Energy-efficiency-map-of...
I don't think the efficiency can be partitioned like that. An L3 charger is supposed to output the same electricity that goes directly into the car's battery, with no additional conversion. An L1 or L2 charger has no conversion inside the charger - it's just a wire and a little electronic tag that says what the amperage is.
The losses are different, but still exist.
In the L3 case there is still a voltage conversion because the input voltage needs to be higher than the battery voltage in order to put energy into the battery. There will be a loss at that stage.
But a big part of the loss during L3 charging is in the battery chemistry. The relatively high charging rate is less efficient than slower charging rates. The high powers involved also generate heat, which often requires active cooling which is an additional reduction in plug-to-wheel efficiency.
In the L1/L2 case there is a conversion from ~240v AC to DC but it's inside the vehicle. Plus the battery chemistry charging losses, but they are much lower than in the L3 case.
These are all ballpark numbers anyhow, so you are welcome to suggest difference values which you believe are supported.
In the L3 case there is still a voltage conversion because the input voltage needs to be higher than the battery voltage in order to put energy into the battery. There will be a loss at that stage.
But a big part of the loss during L3 charging is in the battery chemistry. The relatively high charging rate is less efficient than slower charging rates. The high powers involved also generate heat, which often requires active cooling which is an additional reduction in plug-to-wheel efficiency.
In the L1/L2 case there is a conversion from ~240v AC to DC but it's inside the vehicle. Plus the battery chemistry charging losses, but they are much lower than in the L3 case.
These are all ballpark numbers anyhow, so you are welcome to suggest difference values which you believe are supported.
Considering ICE is less than 40% thermal efficiency of the fuel, I'd say it works out just fine.
But fast charging in general should only be used when there's no voice - it's a lot harder on the battery. Better to slow charge overnight.
But fast charging in general should only be used when there's no voice - it's a lot harder on the battery. Better to slow charge overnight.
With something like this, throwing in solar makes a lot of sense (IMO). There are already batteries involved so you could use solar as the primary recharge mechanism with the grid as a backup.
A single apartment complex could almost certainly not cover enough space with solar panels in order to charge a battery to accommodate this.
That's the neat thing, it doesn't have to. Every kWh that goes into these batteries is a kWh not purchased from the grid. The payback for the solar panels would very quickly add up.
In fact, trying to 100% charge the batteries via solar would not be the most economical way to operate as then you are just wasting money sending power back to the grid.
In fact, trying to 100% charge the batteries via solar would not be the most economical way to operate as then you are just wasting money sending power back to the grid.
IMO, Fast charging is really only necessary for long trips.
Since L2 is more than enough to charge overnight, I'd rather see every parking space get a 30A 240V plug (which should be considerably cheaper than charging stations), with some shared metering to not overload the circuit, but also enough to fully charge all EVs overnight - essentially a single L2 charging station, that moderates load over a large number of plugs.
Since L2 is more than enough to charge overnight, I'd rather see every parking space get a 30A 240V plug (which should be considerably cheaper than charging stations), with some shared metering to not overload the circuit, but also enough to fully charge all EVs overnight - essentially a single L2 charging station, that moderates load over a large number of plugs.
> I'd rather see every parking space get a 30A 240V plug
The whole crux of TFA is that this isn’t feasible to retrofit to existing apartment complexes:
> For many others, the parking spaces will be owned by the condo association or co-op, complicating the idea of giving each EV driver their own plug. Here, shared solutions make more sense, perhaps starting with one or two shared level 2 chargers as a pilot—often this won't even require extra work to the electrical panel. Costs are a little higher than for a home level 2 charger—between $7,500–$15,000 per charger, perhaps.
> But for larger developments, scaling up level 2 chargers can quickly become prohibitively expensive. Older buildings may well need their electrical infrastructure to be upgraded, and running copper wiring across parking lots starts to add up fast.
The whole crux of TFA is that this isn’t feasible to retrofit to existing apartment complexes:
> For many others, the parking spaces will be owned by the condo association or co-op, complicating the idea of giving each EV driver their own plug. Here, shared solutions make more sense, perhaps starting with one or two shared level 2 chargers as a pilot—often this won't even require extra work to the electrical panel. Costs are a little higher than for a home level 2 charger—between $7,500–$15,000 per charger, perhaps.
> But for larger developments, scaling up level 2 chargers can quickly become prohibitively expensive. Older buildings may well need their electrical infrastructure to be upgraded, and running copper wiring across parking lots starts to add up fast.
This battery-backed fast charger doesn't really help to charge the whole complex. How long does the battery last? What is the throughput?
Also, think of the trouble of trying to coordinate times and moving cars around. Everyone wants to charge in the morning, some people are smart enough to charge when get home. Nobody wants to get notification and go move their car in middle of dinner or breakfast.
I found a site with the cost, it is $58k for the battery-backed version. That pays for 5-10 level 2 chargers. Also, I'm not sure it changes the overall situation, cause either pay for wires, batteries, or time.
Also, think of the trouble of trying to coordinate times and moving cars around. Everyone wants to charge in the morning, some people are smart enough to charge when get home. Nobody wants to get notification and go move their car in middle of dinner or breakfast.
I found a site with the cost, it is $58k for the battery-backed version. That pays for 5-10 level 2 chargers. Also, I'm not sure it changes the overall situation, cause either pay for wires, batteries, or time.
Once again the economic argument for retrofits is spelled out in TFA (I’ve now quoted 80% of it)
> Faced with the install costs for a dozen 2 chargers, a battery-buffered DC fast charger starts to look like an attractive alternative. These use an existing electrical feed to trickle-charge a lithium-ion battery pack that can then DC fast-charge an EV, rather than requiring hundreds of kilowatts. Instead of taking 6–10 hours to recharge with AC power, about 30 minutes is usually sufficient to return most EVs to 80 percent state of charge with a DC fast charger.
> A condo building in Miami, the Marina Palms, recently made just this decision after a boom in the number of residents with EVs created a need for more charging capacity than its six existing level 2 chargers could offer. It went with a ChargeBox from ADS-TEC Energy, which is capable of charging at up to 320 kW.
> "That was one of the biggest appeals, that we didn't have to work with the electrical infrastructure of our development or grow it or whatever, just to get this charger installed. I think we have 200 kW in the power grid on that side, and we're using 100 kW. The other way [with multiple level 2 chargers] we would be using a minimum of 140 kW, if not the whole thing, and then we have no buffer for something else we might be doing like—for instance a car lift or that type of thing," explained George Barriere, general manager for the Marina Palms.
> If the costs are comparable, there's another benefit to picking a DC fast charger in place of a bank of AC plugs—it takes up less room. "We didn't use anything from our inventory of parking, which is the biggest problem for condos—lack of parking. So, we would have to have 20 parking spaces for 20 level 2 chargers in order to service the same number of vehicles that we're doing with two parking spaces [with a single level 3 charger]," Barriere told me.
> Faced with the install costs for a dozen 2 chargers, a battery-buffered DC fast charger starts to look like an attractive alternative. These use an existing electrical feed to trickle-charge a lithium-ion battery pack that can then DC fast-charge an EV, rather than requiring hundreds of kilowatts. Instead of taking 6–10 hours to recharge with AC power, about 30 minutes is usually sufficient to return most EVs to 80 percent state of charge with a DC fast charger.
> A condo building in Miami, the Marina Palms, recently made just this decision after a boom in the number of residents with EVs created a need for more charging capacity than its six existing level 2 chargers could offer. It went with a ChargeBox from ADS-TEC Energy, which is capable of charging at up to 320 kW.
> "That was one of the biggest appeals, that we didn't have to work with the electrical infrastructure of our development or grow it or whatever, just to get this charger installed. I think we have 200 kW in the power grid on that side, and we're using 100 kW. The other way [with multiple level 2 chargers] we would be using a minimum of 140 kW, if not the whole thing, and then we have no buffer for something else we might be doing like—for instance a car lift or that type of thing," explained George Barriere, general manager for the Marina Palms.
> If the costs are comparable, there's another benefit to picking a DC fast charger in place of a bank of AC plugs—it takes up less room. "We didn't use anything from our inventory of parking, which is the biggest problem for condos—lack of parking. So, we would have to have 20 parking spaces for 20 level 2 chargers in order to service the same number of vehicles that we're doing with two parking spaces [with a single level 3 charger]," Barriere told me.
This is the most reasonable solution as far as I’m concerned. There are still challenges related to this he electrical service the building is provided. For example you may find the building doesn’t really have enough energy to provide every spot L2 charging.
1 L3 spot doing 150kW translates to ~15 L2 spots or ~100 L1 spots.
For the same power distribution, an apartment complex could easily do several L2 spots and L1 for everything else.
With my 11 mile commute, L1 was almost viable (catching up on charge over the weekend).
If both work and apartments had L1, that'd be enough for most people commuting.
For the same power distribution, an apartment complex could easily do several L2 spots and L1 for everything else.
With my 11 mile commute, L1 was almost viable (catching up on charge over the weekend).
If both work and apartments had L1, that'd be enough for most people commuting.
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There are load management/load sharing products available for EV chargers today. Here’s a white paper from Eaton: https://www.eaton.com/content/dam/eaton/products/emobility/e...
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Everyone wants 60A minimum at 240v. But 30A is just fine, you’re home all night to charge anyway
A quick google query says that efficiency of L2 residential EV chargers is somewhere in the neighborhood of 85%, and for DC-DC chargers the efficiency is in the order of 90%. I don't know nearly enough about this to state anything definitively, but it sounds like the efficiency losses start to accumulate pretty quickly.
I wonder what the break-even point is in terms of cost compared to an average ICE vehicle.
Apply a healthy dose of "Don't let perfect be the enemy of good enough" of course, but I am curious about the economics at play.