Third try at this. Finger problems plus one disappeared.
johnlocke said:
GRA said:
johnlocke said:
Unless you hardwire the L2 charger, you're limited to a 50 amp plug. furthermore if you are drawing current for more than 3 hours, you're limited to 40 amps max out of that plug or 9.6 KW. There are plug-in chargers that can do that. Now assuming a100KH battery and 80% discharge (90%-10%), 90% efficiency and 240VAC, you need 9.5 hours to charge back to 90%. If you use a 32A charger instead then you're looking at 11.5 hours. Either way, plug it in when you get home and you'll be charged up in the morning. And who says you have to have a full charge in the morning anyway? Won't 60-70% be enough for the day? And how often are likely to discharge to 10% or less.
DCFC charging rates might be a problem if you're pressed for time, but overnight charging with a typical L2 isn't a problem.
I disagree that you'll want to take that much time to charge, as utilities more and more go to ToU rates with restricted hours. SDG&E only has a 6 hour super off-peak window, 12M - 6a.m. I agree that 40A (so that you can use a NEMA 14-50 on a 50A circuit) is reasonable for rental property, or anyone who wants to have the option of portability provided by using a plug-in EVSE. Personally, I'd routinely charge no more than 50-60% (20 or 30% - 80%) and except in extreme circumstances would normally limit myself to 70% max. (20-90%). I've been considering what I'll recommend to my landlord when the time comes, and am thinking that I'd suggest a 60A circuit terminating in a NEMA 14-50 receptacle. That way the occupant can always choose to hardwire it instead for 48A, a simple swap out rather than re-wiring.
Public L2 is a different matter, as those won't need portability, and you want people to be able to get a substantial charge in 2-3 hours (dinner and a movie, say) as well as overnight use.
Restricting to 30-32A or even 40A assumes that packs won't need to continue to grow beyond 100kWh so that they can provide full replacement for fossil-fueled ICEs, and that's extremely unlikely (barring [PH]FCEVs), so 48A or better is what we should aim at. Initially the public ones may be shared some or all the time, but eventually you'll need full power for each EVSE.
Even if you install 6 gauge wire, you can only pull 40 amps out of a 14-50 plug for more than 3 hours by code. The breaker can't be more than 50A if there's a 14-50 plug.
Yes, wwhitney cleared that up; I thought it was okay to install a lower-amp receptacle on a higher-rated circuit, as (barring DIY) any appliance using a 14-50 plug would be 50A or less (40A for an EVSE).
johnlocke said:
Do you really think the landlord is likely to install larger gauge wire on the premise that someone in the future might want to hardwire a charger? He might let them pay for that improvement if they were lucky.
It it affects the desirability of the property, they might. Alternatively, it will be required by code in the future. Given the current illegality of installing a lower-rated receptacle on a dedicated higher-amp circuit, it likely won't happen (unless the code is changed). As for who pays, I've certainly considered paying for a higher-amp circuit than the landlord wants to when the time comes, just so I can buy an EVSE with a 14-50 for emergency use on trips. Whether I do so will depend on how road-trip DCFC infrastructure develops in the meantime. Note that given the intermittent use my car gets,
I could get by with just L1 plus DCFC for emergencies. People with greater daily usage couldn't.
johnlocke said:
If you are talking about destination chargers, why would you expect them to provide you with more than 40 amps? It's a convenience feature. In 3 hours you could suck down 20 KWH anyway.
You're correct, it _is_ a convenience feature, and maximizing convenience is necessary to get consumer acceptance. Note, most public L2s will be 208 not 240V, and 208V/48A is 9.984kW, only 4% more than 240/40 so essentially the same. 208/40 is about 8% more than 240/32, so again practically the same.
johnlocke said:
If your utility limits your lowest cost hours, then you might need to charge on two consecutive nights instead of one. If you need to charge faster than that, DCFC is the answer, not 11KW L2.
Again, convenience. We're not talking about people with guaranteed parking/charging spots.
In that vein, I'm reminded of a former girlfriend who, when living in San Francisco, often had to park in bus stops because she was unable to find legal street parking within several blocks of her apt., and she didn't feel safe walking that far at night (working swing shift). She'd hopefully hear her alarm a few hours later and move her car when the early birds went to work before the buses started running. She sometimes didn't, and had a couple grand in parking fines when I met her.
There are far more on-street parking spaces than there'll be chargers for a long time to come. Others may not be able to find a convenient place to charge two nights in a row, or you may have to share chargers on a schedule in a MUD off-street setting. Eventually they'll be enough chargers for everyone, but that's decades away.
johnlocke said:
As far as batteries being larger than 100KWH in the future, maybe for pickups and delivery vans but not for cars. 300-400 mi range is more than adequate and carrying the extra weight for capacity that you don't use is detrimental to efficiency.
We disagree on your first point. If batteries were capable of 300-400
highway miles at realistic speeds with reserves adequate to get them to the next charging station beyond the intended one, plus allowances for hotel loads, could be repeatedly charged in the time it takes to eat at a fast food restaurant
and do the same distance again, and would provide that range for the life of the car, then we would agree. They can't yet. To take one example, the Ionic 5 can charge from 20-80% in 15 minutes, but per Bjorn Nyland its full range (100%-0%) at 75 mph is only 180 miles (hotel loads unstated). 60% of 180 is 108 miles, and plenty of western freeways have speed limits or are moving at 80mph. Do you want to be forced to stop every 1:00-1:20 to charge for 15 minutes? Are DCFCs even spaced that closely together on the route?
If so, is 20% enough of a reserve to get you to the next FC beyond that? Are you willing to use a wider SoC range regularly, knowing that it will cause accelerated battery degradation? I mentioned in another topic, the best-selling ICE cars in the U.S. have (EPA combined) ranges between 450-500 miles, so 400+ Hwy. Manufacturers aren't providing that range if there's no consumer demand for it, and unlike BEVs you can if you wish repeatedly use all of it without affecting the long-term viability of the car.
On your second point, I've been making the weight/efficiency (along with stretching the battery supply) argument in favor of fossil-fueled PHEVs -> PHFCEVs and/or syn- or bio-fueled PHEVs in the PHEV topic, with much pushback from battery-only advocates. Please feel free to support my argument there.
johnlocke said:
Delivery vehicles will have charging stations at their home base capable of charging them at whatever speed the manufacturer deems optimal for their use.
No argument from me, I'm talking about private not commercial vehicles, although the same basic consideration applies. Unless you've got guaranteed charging, you're not going to switch.
johnlocke said:
Semi's will have DCFC chargers
For regional distribution, but the payload weight and time penalties call for other techs for long-haul, even more than is the case with private vehicles. Current BEV semis apparently have about a 25% payload penalty vs. diesels at longer ranges, and that's
after the extra 2,000 GVWR boost (82 vs. 80k) they're allowed as AFVs, to the detriment of our roads. That's not going to be acceptable unless they're restricted to hauling fluff commodities.
johnlocke said:
Pickups will be likely charged overnight for most business use. People who haul trailers will be the oddball case. Likely charging overnight for normal use and DCFC when hauling long distances. People tend to buy pickups for specific needs, so a range of battery sizes and hauling capacities are likely.
Again, while trailer-pulling is the most demanding case, plenty of people take road trips without pulling trailers. I don't see many trailers in national parks. NRAs are another matter.