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Discussion Starter · #1 ·
I'm looking into a L2 charger and debating between the 32 and 40A-output models. My 2017 Bolt will charge at up to 32A off an L2, but it's not clear whether it can pull additional power for auxiliary purposes while charging @32A - say for battery conditioning, or preconditioning the interior, or what-have-you. Google and forum searches haven't turned up anything relevant. Anybody got any ideas on where to look, or a cited reference?


-Watts
 

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may need to revisit the Weber video on the wiring for clues. thinking it's one harness from the charge port to the onboard charger. the wire gauge would be a clue if it's only sized for 32 amps or possibly oversized for a larger load. next clue might be a fuse in that part of the circuit. maybe someone has their hands on a wiring diagram.
 

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I doubt it will ever pull more than 32 amps - many many people including myself have plugged the bolt into >32 amp L2 chargers and never seen more than 7.68 kW draw (expected KW for 32 amps).

I recommend installing at least a 50 amp circuit which can yield a 40 amp charge rate as the incremental cost between 40 & 50 amp is negligible and will setup you very very well for any future EV's that can charge at greater than 32 amp.

Installing the charge is mostly a labor expense and the incremental difference between 40 amp wire/equipment and 50 amp wire/equipment isn't a significant part of the install overall cost.

but if you do install more than 40/32 amp don't expect the Bolt to benefit in any additional manner.

for true future proofing I recommend pulling 100 amp rated wire to a sub panel and then throw what ever breaker and wire you need for your current planned charger, that way in the future if you want to upgrade your charging infrastructure for a faster EV or multi-EV charging scenario you have the necessary capacity and it a much cheaper and easier install to upgrade/add charging capacity.

https://www.chevybolt.org/forum/82-...ion-charging-opinions-long-time-ev-owner.html
https://www.chevybolt.org/forum/82-charging-batteries/7138-charging-opinions-long-time-ev-user.html
 

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I'm looking into a L2 charger and debating between the 32 and 40A-output models. My 2017 Bolt will charge at up to 32A off an L2, but it's not clear whether it can pull additional power for auxiliary purposes while charging @32A - say for battery conditioning, or preconditioning the interior, or what-have-you. Google and forum searches haven't turned up anything relevant. Anybody got any ideas on where to look, or a cited reference?
It'll pull a max of 32A, no matter what it is doing. If you preconditioned and charged at the same time, it'll charge more slowly. Battery conditioning typically happens after the charge is complete.
 

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I recommend installing at least a 50 amp circuit which can yield a 40 amp charge rate as the incremental cost between 40 & 50 amp is negligible and will setup you very very well for any future EV's that can charge at greater than 32 amp.

Installing the charge is mostly a labor expense and the incremental difference between 40 amp wire/equipment and 50 amp wire/equipment isn't a significant part of the install overall cost.
+++
 

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As mentioned already, the EVSE won't pull more than 32A. That said, I'd still shop for a 40A just to future proof, and they shouldn't cost much more. My guess is most EVs going forward will have 40A L2 capability.

You advice is sound, but that "EV upgrade" to which people refer is buying a new car, not having your old EV modified or "upgraded" to accept 40 amp. Ditto for Level 3 "upgrades". There are DCFC EVSE capable of sending out 150kW (with 200-250 kW on the drawing board or in prototype. The Bolt can only accept 55 kW. (I used to think the max was 50 kW but someone corrected me.) To benefit from kWs over 100, you may have to change brands. The Bolt has no plans (of which I know) to put out a model that is "wired" for the higher power.
 

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You advice is sound, but that "EV upgrade" to which people refer is buying a new car, not having your old EV modified or "upgraded" to accept 40 amp. Ditto for Level 3 "upgrades". There are DCFC EVSE capable of sending out 150kW (with 200-250 kW on the drawing board or in prototype. The Bolt can only accept 55 kW. (I used to think the max was 50 kW but someone corrected me.) To benefit from kWs over 100, you may have to change brands. The Bolt has no plans (of which I know) to put out a model that is "wired" for the higher power.
The more important thing to look at with DCFC is not the kW rating, but the amperage.
The Bolt has a 150A limit when utilizing DCFC equipment. Pack voltage is 350, and a slightly higher voltage is utilized when charging - in the case of the Bolt ~ 370.
There are "50 kW" DCFC stations out there that are 125A and others that are 100A. The Bolt will charge faster on the 125A equipment

The CCS spec for HPC350 (350 kW DCFC) requires a minimum of 500A @ 500V and 380A @ 920V. The Bolt would charge @ 55 kW on these (or anything that can provide at least 150A @ 400V) if SOC and temperature are in the right zone.

The official EPA application Chevy submitted lists off-board charging at 50 kW, and Chevy has requested that it be listed that way. (ChargeWay has/will reduce it from a "Green 5" to a "Green 4")

But to the original question - as noted by several above, the on-board charger will never pull more than 32A from the EVSE, even if the EVSE advertises a higher amount available. The car will internally allocate the 32A for charging/conditioning.
 

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Isn't there a limitation put on the residential kw's that can be drawn from the utilities? I remember reading someplace that the neighborhood utility boxes would have a hard time keeping up with higher charging rates.


Also, 7.68kw times 10 hours times 4 miles per kwh (roughly highway usage) is a little over 300 miles. In 24 hours of charging, its 738 miles. When would you really need 40 or even 100 amp EVSE service for residential situations?
 

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Modern homes have 200A service to the panel, so as long as normal electrical use is not likely to exceed 160 continuous amps, higher rates of charging are permissible. You could even upgrade the service level of the home to support higher rates of charging. Tesla wall chargers go up to 80 amps.

I can't imagine most people needing more than 32A, but why not have it available just in case, especially if the incremental cost is low?

As was mentioned, some people have TOU pricing that gives only an 8hr window to charge off-peak. It's conceivable that a nearly empty Bolt can't get a full charge within that amount of time on 32 A. In that case, faster charging might be of use to some people.
 

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Discussion Starter · #12 ·
@XJ12 - I pulled up the tech manual/wiring diagram. It shows the two power pins in the J1772 as being fused at 50A... so I'm not sure that tells me much but it does leave open the possibility that it could be engineered for 40A sustained... which I would probably read as occasional extended peak draws of 38A, assuming one derates auto fuses the same way one derates building wiring/loads.

@daveo4Bolt - noted, and there's a reasonable argument to be made that it's costing me more to think about this than pay the differential for 40A. The pedant and engineer voices in my head, however, are carrying the day. :) Your point about the subpanel is excellent - that is in fact what I had planned to do.

@DucRider - I looked into DCFC for the house but a) it's such ludicrous overkill that even I can't justify it even if it wasn't $10K, and if I recall they mostly require 3-phase service, which I don't have. I will be upgrading the house's 60s-vintage 150?A service to 400A, to clean up some legacy / maintenance issues, pull 100A to the driveway (for future 2nd-driver EV, and hopefully later a detached 2-car garage and radio tower), conversion to all-electric appliances to work towards carbon-neutrality), add backup generator hookups, etc. I asked the power company what 3-phase would cost me and the answer was "at a minimum, cable costs from the nearest point where it's available to your (end of the line) residence". So I think L2 is about my speed for now. :)



After 30 minutes on the phone with GM corporate and a very disinterested (and uncited) statement by technical assistance that 32A is the max it'll draw, I'm tabling this. I plan to install a 100A subpanel with a 50A breaker/weather-proof outlet, and a 40A EVSE for starters. Then I'm going to see if I can catch it pulling more than 32A (battery conditioner running, cabin heater running, ham radio amp drawing, who knows what.)


Documenting this for posterity in case someone else (or future-Watts) finds actual engineering citations for what/why it can/not draw more than 32A.


Thanks to all who replied!
 

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Modern homes have 200A service to the panel, so as long as normal electrical use is not likely to exceed 160 continuous amps, higher rates of charging are permissible.
Electricity utilities "over-subscribe" their "last mile" feeds. Just because a block of 20 houses or so have 200A electrical panels (about 48kW in theory) doesn't mean they provide transformers on that block that can actually handle that load. It would be wasteful for them to do that, since it's never the case that everyone on the block is drawing that much power simultaneously.

The average power requirements for a block of houses are going to increase as EVs continue to penetrate into the market, especially overnight. But the utilities monitor power consumption and they'll add capacity as it's needed. There's nothing they love quite like customers buying more and more power from them.
 

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Right, but if most people are charging off-peak, then nothing needs to be upgraded since the averaged load is below peak.

If EVs cause peak draw, then that would necessitate infrastructure upgrade, but not until that point is reached. We're a long way off from EVs causing peak load rather than AC units.
 

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Electricity utilities "over-subscribe" their "last mile" feeds. Just because a block of 20 houses or so have 200A electrical panels (about 48kW in theory) doesn't mean they provide transformers on that block that can actually handle that load. It would be wasteful for them to do that, since it's never the case that everyone on the block is drawing that much power simultaneously.

The average power requirements for a block of houses are going to increase as EVs continue to penetrate into the market, especially overnight. But the utilities monitor power consumption and they'll add capacity as it's needed. There's nothing they love quite like customers buying more and more power from them.

During a major remodel, I replaced my main (was 100A), with 200A, and put a 100A sub in the garage, with two 50A circuits terminated in 14-50s. I've also got six 20A circuits in there, too. The city inspector initially disallowed me from landing my solar PV in the sub, because it "would overload the 100A panel". He was pretty adamant until I repeatedly explained that solar puts power *in* to the sub, and if anything, would *reduce* the current being sent to the sub from the main. He obviously missed the PV day at "Inspector School".>:)
 

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We're a long way off from EVs causing peak load rather than AC units.
My impression of A/C units is pretty much limited to the portable plug-in ones that we see here in temperate Vancouver BC. They'd be limited to less than a couple of kW of power since they use standard 120V/15A circuits. I'm guessing that built-in central A/C is prevalent in the warmer southern states - what kind of power do those draw?
 

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most central AC units are on a 30-60 amp circuit - with a lot in the 40 amp (10,000 watt) range - many larger homes have 2 or 3 units鈥o it's like running a EV charger from noon until 7 pm - almost continuously -

at night if the AC units are not running - a 40 amp EV charger might actually be LESS load than a house's 2 AC units - and not all houses have EV chargers - so again even less load鈥

I'd say until we have a significant penetration of EV's the AC loads of most residential neighborhoods is far more load than EV charging on a residential basis.
 

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Electricity utilities "over-subscribe" their "last mile" feeds. Just because a block of 20 houses or so have 200A electrical panels (about 48kW in theory) doesn't mean they provide transformers on that block that can actually handle that load. It would be wasteful for them to do that, since it's never the case that everyone on the block is drawing that much power simultaneously.
Indeed. When we lived in Atlanta the little apartment building next to us added split-system retrofit AC to all of the 12 units, one compressor per apartment. The installation part was done competently and correctly but what was not handled at all was contacting the electric utility with updated information. The first prolonged warm day of spring saw the transformer on the pole outside the building venting spectacularly (all over the parked vehicles below) before dying horribly, Presumably the transformer's fuse was incorrect. That transformer was also our drop as well as another home next to us.
 

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My impression of A/C units is pretty much limited to the portable plug-in ones that we see here in temperate Vancouver BC. They'd be limited to less than a couple of kW of power since they use standard 120V/15A circuits. I'm guessing that built-in central A/C is prevalent in the warmer southern states - what kind of power do those draw?
I'm with you in having only owned window AC units. On the 45th parallel, there's not many days of cooling needed if the house is opened up at night to cool off and closed up during the day.

That said, most EVs in the Americas are sold in CA, and they're the ones with large peak loads in the late afternoon.



EVs will add some small amount to peak loads, but in general should tend to bring base load demand up. Bringing base load and peak load demand closer together tends to improve the efficiency of meeting overall electrical demand.

When EVs become commonplace, there will no doubt be infrastructure improvements made, but in general should represent an overall net positive addition to the grid. By incentivising charging during off-peak times, and possibly incentivising delayed charging during peak times, infrastructure could be made more robust by their addition.

BMW had experimented with a voluntary program where participants would be sent alerts asking them to delay charging their vehicle during unusually high demand. They could opt out and charge as normal, or agree to delay. These sort of concepts could bring stability, especially if the utility could be given direct control to delay charging up to a time specified by the owner.
 
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