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Discussion Starter · #1 · (Edited)
I'm prepping for delivery day by getting a charging strategy ready for the Solterra and future cars completed. I figured I'd document for others. Some of this is unofficial so I listed the basis for those claims.

Prerequisites:
  • 80% Rule: The US electric standard is complex and for valid reasons a 50A breaker cannot supply 50A continuously. Rather it can supply 100A for a fraction of a second (motor starting), 60A for a few seconds. 55A for a minute, 50A for an hour and 40A continuously (made up numbers, but idea is directionally correct).

    Since we plan to charge for hours on end, we must use the "continuous" rating of the circuit, which is the breaker size minus 20%. Voltage does not matter here. Thus the 80% rule means:

    -- Breaker/wiring at 50A provides 40A usable
    -- Breaker/wiring at 40A provides 32A usable
    -- Breaker/wiring at 30A provides 24A usable
    -- Breaker/wiring at 20A provides 16A usable
    -- Breaker/wiring at 15A provides 12A usable

  • Charger or EVSE? I'll use charger below, but technically they are Electric Vehicle Supply Equipment (EVSE).

  • GFCI: should be added to all outlets (excludes hard-wired stations). They are expensive and hard to find right now (~$100). Codes changed on this ~5 years ago, so it's mandatory in some places, optional in others, and always a good idea. Most portable chargers do NOT have GFCI protection in them. Hard-wired stations typically do.

120V Charging:
  • 15A Outlet: Included with the car is a 12A charger (EVSE) for common household 15A outlets. There is a feature in the manual to lower this down to 8A if needed (eg circuit shared with other items). Expect 2 miles added per hour at 8A. 3 miles added per hour at 12A. Slow, but if you are able to be plugging in constantly and only drive around town, this may get the job done.

    Basis: Safe assumption based on marketing, prior cars from both Subaru/Toyota, and liability of including anything faster.

  • 20A Outlet: Upgrade to 16A charger on a 20A outlet. This is where things get murky as various venders fudge things here, but at minimum the circuit should have a 20A breaker and 12 AWG wiring. Ideally it'd be a proper 20A receptacle and plug too, but many 16A ESVE are ignoring this part. Some, but not all, houses already have this wiring in place. Many business will too. If adding a 240V outlet is prohibitively expensive or this is an occasional use location (eg parent's house), look to see if using an existing 20A circuit is possible.

    Basis: Manual states max charge rate is 16A and prior Toyota Prime hybrids with 6.6kW onboard charger work at 16A.

  • 30A Travel Trailer Outlets: This was a disappointment as I have access to these plugs, but it appears the charger is limited to 16 amps per the manual at 110v. Others vendors (eg VW) have a similar ~16A limit. Tesla will charge using the full 24A (80%) at 110V. In this case, you could get a 30A to 20A adapter, and use your 12A or 16A charger per above. Using the supplied charger on the 30A > 20A adapter will still be limited to 12A.
240V Charging:
  • Car: can charge up to a maximum of 27.5 amps.

  • Ideal Circuit: Hard-wire a charger to the wall or install a 14-50 NEMA outlet with 50A breaker (6AWG wire). Future-proof and no thinking required. This is the industry standard practice and should be done in 95% of cases if possible.

  • Ideal Charger (EVSE): There are no 27.5A chargers. You can use higher-rated chargers (eg 32A/40A) but car will only pull it's maximum of 27.5A (6.6kW). The downside of going overly large (eg 48A) they will have bulkier (less flexible) cords and require 60A+ breakers and associated wiring. 32A EVSE is a good sweet spot of price/flexibility/etc. 40A works too. I'd stay ways from 48A+ chargers.

  • Undersizing: Anything less than a 40A breaker + 8AWG wiring is undersizing and requires extra care. The problem is a problem is that the car needs to know it's attached to an undersized circuit otherwise it will try and pull 27.5A and trip breakers (or worse start a fire!). It's the job of the charger/EVSE to tell the car the maximum charge rate. Further challenging is the Solterra does not allow you to derate the current manually (unlike others eg Tesla). So if you plug into a 30A 240V circuit, which should only pull 24A using the 80% rule, the EVSE must properly tell it to pull 24A otherwise the car will attempt to pull the full 27.5A.

    So in this case, first I'd suggest avoiding it all-together by installing an "ideal 50A circuit" above. If you do go this route, ensure you have an EVSE that is "programmable" in some manner so you can tell the EVSE (which tells the car) that the circuit can only safely hand 12A/16A/24A if you are on a 15A/20A/30A circuit.
DC Fast Charging:
  • 100kW limit: Adequate, but not fast by today's standards.
  • Real World Performance: Initial tests of BZ4X are showing that 100kW is optimistic. Charging rates while at a 0-50% state of charge in the battery is adequately fast to get you back on the road, but charging in the 60-100% range becomes painfully slow and should be avoided. Plan on only fast charging from 0-70% or so.
  • Derate: Per the manual you can manually choose to DC fast charge at maximum of 50kW, 75kW or full 100kW (default). The only reason I can see using this is if you are at a DC charger at a shopping mall or restaurant and know you need 2 hours. Then the slower charge (50kW) is a bit easier on the pack's longevity. Even then it only makes sense if paying by the kWh. Some states by law require payment to be done by the minute, and thus going slower is costing more than you are benefiting.

    If you must fast charge weekly, the Solterra is not a great choice compared to the competition. That said, most reading this will only fast charge at most 3 times a year, so what's an extra 3 hours over a year being slower does not really matter. The Solterra is not a regular road tripper compared to the competition. It's great for those that can charge at home nightly.

What was missed? Anything incorrect? Let me know and I'll update.
 

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@loki You mentioned that "Further challenging is the Solterra does not allow you to derate the current manually (unlike others eg Tesla)." However, the manual does state that you can select 8A or 16A max charging current. You actually mentioned that above when discussing 120V charging. Do you believe that does not apply to 240V charging? Or did I misunderstand your statement?
 

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Discussion Starter · #4 ·
My Charging Plan:

Primary Charging Location:
NEMA 14-40 outlet with 50A breaker/wiring in garage w/ 32A charger. This will cover 95% of needs and allow upgrade to 40A charger in future if needed.

Secondary Locations:
This is where things became difficult and the above research into 20A/30A @ 110v and undersized 240V circuits was needed. The solutions needed to be fool-proof -- no accidentally drawing 27.5A from a 20A circuit. These secondary locations will be used infrequently, but when they are needed, they will be very handy. eg. I couldn't justify spending any major money at these locations, so I have to use what's available. A sample of these places are: campgrounds, driveway too far from garage 14-40 plug, parent's house, brother's house, etc.

So here is what I've come up with:
  • Programmable 32A EVSE (see below for exact model) with 12A/16A/24A/32A settings. EVSE plugs being used are 5-15 / 5-20 / 6-20 and 14-50. Others exist, but do not see needing them now.

  • Home Driveway -- We have 12/3 wiring already to both sides of our driveway feeding normal outlets. I found "dual voltage 20A duplex receptacle" receptacles that I didn't know existed prior. They have both a common 5-20 120V receptacle as well a 6-20 240V receptacle in one box. Leviton #5842 is what I plan to purchase. This means we can still use standard 120V outlet items (eg vacuum for car) as well as a 16A @ 240V Level 2 Charger (~14 miles added per hour). This is enough for everyday use and when the garage stall is filled, we can continue charging outside without issue. The best part of this is using the existing wiring. New dual-pole GFCI breaker (~$100) and outlets (~$17 each) and we are set.

  • Campgrounds -- 14-50 direct when available or TT-30 plug to 5-20 (20A) adapter that we use camper if needed. It's common for the 120V outlets to be 20A anyways, so might be direct.

  • Driveway Surfing: One house I'm converting a 12/3 outlet to a dual voltage outlet similar to above. Another installing 14-50 outlet. Other will just use 12A or 16A as available.
EVSE Selection
  • I wanted a properly certified charger and it to be mobile. The included charger will go straight to storage or ebay.
  • I almost bought a new the Ford Mach-e Charger from Ebay with 15A and 14-50 plugs adapter plugs on it. It automatically sets the rate to 12A or 32A based on plug attached. But no plugs are currently available for 20A (120V or 240V). This is a great option if (a) you only have access to 15A and 14-50 plugs or (b) they come out with additional plugs in the future. I expect more plugs to become available, but might be 1 month, might be 5 years.
  • Chargers that use a button to program the rate would work, but require using dogbone adapters and understanding which rate to use for which adapter. This is a viable strategy, particularly if you label each dog-bone adapter with its limit, but feels clumsy to me. This is my wife's daily driver and family members also regularly swap cars (eg truck for car swap). I wanted no-thought and fool-proof.
  • There is only one charger that meets the above, and it's the Tesla Universal Mobile Connector. It has 9 different plug adapters you can choose from (NEMA 5-15 / 5-20 / 6-20 / 14-50 / etc). It's small, quality and proven. The only reason I dismissed this early on was it uses the Tesla plug, not the standard J1772 plug. I didn't want to use a Tesla to J1772 adapter (~$150), as that is clumsy.
  • It turns out that you can have a J1772 put onto the Tesla charger directly (eg. tucsonev.com) -- with that I'm done. Two Tesla mobile chargers -- one semi-permeant in the garage on the 14-50 outlet. The other to reside in the car trunk with all the 120V/240V adapters. No need to explain anything to anyone -- match the plug with the receptacle and connect.
Hope the above is helpful to someone. Tried to share the thought journey to save some others the potential pain of discovery.
 

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Discussion Starter · #5 ·
Last part is about kW charging rate for DCFC, not Amps.

Re-edit the post to update it and I’ll delete this post. Nice summary.

Some EVSE recommend to not use on a GFCI protected outlet (usually GFCI breaker).
Wow...guess I had amps on my mind so long writing the above. Thanks for the correction.

Regarding not using GFCI breaker:
  • If it's hard-wired, no problem there. They recommend that b/c there is a GFCI circuit within the charger.

  • If it's a "stationary" charger -- meaning fixed wall mounted with an internal GFCI, but uses a plug, technically that would break current code, but I would not be too bothered by that. The outlet/plug is quasi-fixed and the charger has internal GFCI.

  • If the plug is to be removed regularly (eg throw charger in car on trip to parents) -- with or without internal GFCI the outlet should have GFCI.
If you can't make one of the three work, time for a different EVSE.
 

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Discussion Starter · #6 ·
@loki You mentioned that "Further challenging is the Solterra does not allow you to derate the current manually (unlike others eg Tesla)." However, the manual does state that you can select 8A or 16A max charging current. You actually mentioned that above when discussing 120V charging. Do you believe that does not apply to 240V charging? Or did I misunderstand your statement?
Exactly.
  • The 120V derate is only 8A or 16A binary. No 10A or 13A.
  • On 240V there is no derate at all.
  • There is a the 50/75/100kW derate on DCFC.
The engineer side of my brain understands this. Two design choices were (a) battery longevity (derate DCFC) and (b) make it super simple to use the car.

The 110A derate from 16A > 8A (which is enforced on both 15 and 20A circuits) is buried in the setting menu -- not really supposed to be changed often. I think this was more a concession to support two cars charging on a 20A circuit (think dealers) and prevent nuisance tripping than a feature Toyota want's to provide.
 

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Good info for North America. But perhaps it should be mentioned that the Solterra doesn't support 3 phase AC charging. So I believe in a typical European L2 setup it will be limited to 3.7 kW.

Perhaps someone from there can chime in on whether it's feasible / common to have a circuit that can supply 240V 27.5A on a single phase to max out the onboard AC charger.
 

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Good thread!

I'd like to get an electrician to install an outlet that is somewhat future-proof. In other words, it would be ideal for a Solterra today but could be used for a Tesla, Polestar, etc. at some point in the future. I'm in the US. Can someone ELI5 what I should look for?
 

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Good thread!

I'd like to get an electrician to install an outlet that is somewhat future-proof. In other words, it would be ideal for a Solterra today but could be used for a Tesla, Polestar, etc. at some point in the future. I'm in the US. Can someone ELI5 what I should look for?
The problem with future proofing is that anything over a 50 amp circuit requires a hard-wired connection instead of an outlet, so to support for example the ability for some Tesla’s to charge at 48 amps, you would need a 60 amp circuit and a hardwired EVSE.

The best/most-practical approach would be a 40 amp circuit with a 14-50R outlet, which will support up to 32 amp charging.
 

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The best/most-practical approach would be a 40 amp circuit with a 14-50R outlet, which will support up to 32 amp charging.
This is the sweet spot considering installation cost, charge speed and practicality (being able to use a portable EVSE). This will meet the needs of the vast majority of users. The only worthwhile future proofing would be to use 6-3 wiring. Then you would only need to change the breaker (to 50A) if you ever want to go to a 40 amp EVSE.
 

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The problem with future proofing is that anything over a 50 amp circuit requires a hard-wired connection instead of an outlet, so to support for example the ability for some Tesla’s to charge at 48 amps, you would need a 60 amp circuit and a hardwired EVSE.

The best/most-practical approach would be a 40 amp circuit with a 14-50R outlet, which will support up to 32 amp charging.
If my electrical system can handle it, I'll have a 60A breaker installed for future-proofing. Hardwire works better anyway, and should be cheaper. I'm not going to be house-hopping. I'll get the ChargePoint Home Flex EVSE, so I'll be ready for whatever EV I get in the future that has up to an 11.5 kW onboard AC charger.
 

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Discussion Starter · #12 ·
The problem with future proofing is that anything over a 50 amp circuit requires a hard-wired connection instead of an outlet, so to support for example the ability for some Tesla’s to charge at 48 amps, you would need a 60 amp circuit and a hardwired EVSE.

The best/most-practical approach would be a 40 amp circuit with a 14-50R outlet, which will support up to 32 amp charging.
Slight correction. The NEMA 14-50 common outlet should generally be installed with a 50A breaker & 6 AWG wire. It's possible to derate it with a 40A breaker and be code compliant, but it's not worth the marginal savings. If using a 32A charger, no need to only install a 40A breaker. Do a 50A breaker/wiring the first time and forget about it for the next 20 years -- especially if you are paying someone to do this work for you.

As I said above, the ideal outlet (vs hardwired) solution is a NEMA 14-50 outlet with 6 AWG wire. Any electrician will understand this.

The Solterra charger maxes out at 27.5A, which is low. Similar standard-range cars usually do 32A. Long range cars can usually do 40 or 48A. EV trucks do up to 80A. My home charging needs are only to recharge from ~20% to 80% in 8 hours (time of use plan). Anything faster is unneeded. 8 hours @ 40A/240V is about 70kWh after losses or 210 mile range in a car. That's pretty future-proof. I rarely drive 210 miles in a day, much less two back-to-back. If I do not top up after the first night, it'd be charged on the second night. Even in a less efficient EV truck, that's ~140 miles in 8 hours. -- plenty. So while 48 or 60A sounds nice on paper, practically speaking it's not overly useful unless you commute very long distances daily. Plus if I was in a pinch, no need to limit to 8 hours of charging, charge from arrival at home until leaving next day.
 

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The 14-50R outlet, 6/3 wire and 50A breaker is exactly my home configuration. It also allows for visitors with RVs to get a full 40A usable at 240V (9.6kW) for air conditioners, etc.

Unless you need higher current and are willing to go the hard-wired route, this results in the highest rated (non-3 phase) configuration for most residences.
 

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Discussion Starter · #14 ·
If my electrical system can handle it, I'll have a 60A breaker installed for future-proofing. Hardwire works better anyway, and should be cheaper. I'm not going to be house-hopping. I'll get the ChargePoint Home Flex EVSE, so I'll be ready for whatever EV I get in the future that has up to an 11.5 kW onboard AC charger.
That's a valid plan for hard-wired. The costs work out to be about the same as you can use a cheaper breaker (GFCI is in wall unit and no outlet), but the wall units tend to be about that much more expensive to make it a wash. If you are never bringing the charger with you, it's a great option. In ~5 years I may replace my truck with a EV truck, and then dedicated high-power circuit makes lots of sense. For lower powered homes, the power sharing features of wall-units will useful with 2 or more EVs in the household.

The one main downside to a wall unit besides obviously portability is if it dies, you cannot easily swap a new one without touching electrical wires. Personally I opted for two identical portable units to make life simple and redundant.
 

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Slight correction. The NEMA 14-50 common outlet should generally be installed with a 50A breaker & 6 AWG wire. It's possible to derate it with a 40A breaker and be code compliant, but it's not worth the marginal savings. If using a 32A charger, no need to only install a 40A breaker. Do a 50A breaker/wiring the first time and forget about it for the next 20 years -- especially if you are paying someone to do this work for you.

As I said above, the ideal outlet (vs hardwired) solution is a NEMA 14-50 outlet with 6 AWG wire. Any electrician will understand this.

The Solterra charger maxes out at 27.5A, which is low. Similar standard-range cars usually do 32A. Long range cars can usually do 40 or 48A. EV trucks do up to 80A. My home charging needs are only to recharge from ~20% to 80% in 8 hours (time of use plan). Anything faster is unneeded. 8 hours @ 40A/240V is about 70kWh after losses or 210 mile range in a car. That's pretty future-proof. I rarely drive 210 miles in a day, much less two back-to-back. If I do not top up after the first night, it'd be charged on the second night. Even in a less efficient EV truck, that's ~140 miles in 8 hours. -- plenty. So while 48 or 60A sounds nice on paper, practically speaking it's not overly useful unless you commute very long distances daily. Plus if I was in a pinch, no need to limit to 8 hours of charging, charge from arrival at home until leaving next day.
The thing is, you can always slow it down. But, it'd be nice to have the versatility to speed it up if the need arises. Some additional needs are you get home late, or you come home and intend to go back out in two or three hours, etc.
 

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Discussion Starter · #17 ·
The thing is, you can always slow it down. But, it'd be nice to have the versatility to speed it up if the need arises. Some additional needs are you get home late, or you come home and intend to go back out in two or three hours, etc.
Agreed. Sorry if I was not clear, I think there are two valid ideal strategies: 50A Outlet (40A usable) or hard-wired at 50A+ circuit (40A+ usable). There are pros/cons to each, but both get the job done satisfactorily with different drawbacks while being reasonably future-proof for additional cars down the line. What's nice is you can switch between the two as well down the road if desired.

I would not recommend installing from scratch 20A / 30A / 40A circuits unless I had a limiting reason such as repurposing existing wiring.

Honestly for me I see another EV in several years when I replace my truck, and at that point I'll probably run a 100A circuit for 80A wall-mount charging if I get another pickup truck, but that's a bit silly to do today when the Solterra can only pull 27.5A. Plus it'd be in the wrong garage stall. At some point you need to call it good enough.
 

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Honestly for me I see another EV in several years when I replace my truck, and at that point I'll probably run a 100A circuit for 80A wall-mount charging if I get another pickup truck, but that's a bit silly to do today when the Solterra can only pull 27.5A. Plus it'd be in the wrong garage stall. At some point you need to call it good enough.
I was in a data center recently, and instead of having power whips (cords) hardwired to each server rack, there was a power distribution system above the server racks into which power connections could be made, on the fly. Kind of like this:


Now, of course something like this is overkill for a garage, but I'd be surprised if one of these busbar companies wasn't thinking about providing something like this for the residential market. (There are a lot more residential houses than there are data centers.)
 

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You can even use the EVSE with the 120V plug that comes with your car to use 240V if you don't want to buy a new one. Just have to rig up your own adapter. That will double the speed of just charging at 120V.
 

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2023 Chevy Volt EUV will ship standard with a dual-level charging cord (EVSE). There are two short cables, one for 120V and one for 240V, that mate with their EVSE. It sounds like the 240V one is limited to a 32A rate, since it wants a 14-50R outlet on a 40A breaker.


 
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