Why is 240V 3x faster than 120V

[Phximiev]

Trying calling the Weights and Measures people and see if they, or the county, will do an inspection...

Phximiev, you're kidding, right? (you forgot the smiley face), as I don't think there is any issue here at all. Blink charges 39¢/kWh (if you're a member) at this station, no matter what the voltage. Since the car's input is current limited, it's simply that the i-MiEV charges slower there than when using his (quite high) voltage at home.

Actually, I'm not. There are numerous examples of those in the measuring and selling business that have over-charged their consumers, which over time amounts to $$$. Given my recent experience with Blink, where they represented that their level 2 chargers charge anywhere from 10 to 25 miles per hour and our charge resulted in only a 5 mile increase in our Volt, something is amiss. We have the Blink app. It fails to provide the kWh provided in the charge with ALL of the charges showing zero and we can't get it from them.

I have other examples where chargers are supposed to be providing a certain amount of charge and don't. Our local EAA chapter officer, Jim Stack, routinely goes around with a charging measurement device and on numerous occasions has found chargers that are not charging correctly. The car, as you correctly point out, may be limited, but that is irrelevant given the representations by the charging companies that they will provide a charge up to that point and don't.

As far as Blink, I am aware that they have a varied charging structure, but that is not excuse for the crappy screens and crappy reporting, and failure to charge. Additionally, today, for instance, I couldn't even read the screen and when I went to start the charge, had to call to confirm the rate and start the charge. It was disappointing after that to only get 5 miles after 45 minutes of charging.

Again, something is amiss. If you desire to speak to Jim, please let me know. He can be found here: https://www.facebook.com/pg/PhoenixEAA/about/?ref=page_internal

 

[JoeS]

...Again, something is amiss...

Phximiev, I'm afraid I can't get excited over this, and I don't believe that's been shown -

1. I'm no fan of Blink (just last week I sent them a trouble report about one of their local charging stations being inoperable), and have more than once been frustrated by their stations' failures

2. The explanations for the differences in charging rates between work and home seem plausible

3. bradleydavidgood777 isn't saying that he's being financially screwed by Blink, but simply noting that there is a difference in charging rates between work and home.

4. Until bradleydavidgood777 makes some measurements of that Blink input current and voltage, I don't think it's worth pursuing. Maybe a phone call to Blink asking them if that EVSE is running on 208vac or 240vac? Certainly don't want to call the 'cops' until we have some tangible evidence of an irregularity between the billed $$ and the kWh put into the car. Our fuel gauge 'bars' alone is insufficient, IMO.

5. Reviewing the user comments on PlugShare, in addition to the usual broken screen and ICE'd complaints there are a couple of postings about 24A and 30A being available. https://www.plugshare.com/location/13538

bradleydavidgood777, are you a Blink member so you get the 39¢/kWh rate rather than the 49¢/kWh rate? Does the Blink statement or screen tell you how many kWh they think they fed your car (and over how much time)?

 

[bradleydavidgood777]

Here is an important fact. I don't pay for it. I pay monthly for the lot and the lot owns the equipment.

This was my largest factor in buying the car. I can charge at work, drive home, do normal errands and get back to work with 3-4 bars remaining. My operating costs have gone down to near zero.

Hi bradley,

Your EV has been unplugged and/or your session at 9th & Arch Parking Lot, Unit #: 209600 has stopped.

If this was not expected, please check your vehicle's charge schedule or make sure that your EV is still plugged in. If you need assistance, please contact Blink Customer Support at 1.888.998.BLINK (2546) or email [email protected].

Connection Start Time: 2018-07-31 07:09:06.0 (ET)
Connection Finish Time: 2018-07-31 11:39:02.0 (ET)
Total Connection Duration: 04:29:53
kWh : 0.0
kWh or Time-based Fee: 0.00
Total Fee: 0.00

 

[PV1]

We're starting to drift off-topic. After driving my i-MiEV for 5 years and noting how numerous different charging stations charge, an EVSE that is capable of 16 or more amps will ALWAYS charge the i-MiEV faster when fed with single-phase, 240 volts from the utility compared to a unit pulling 208 from a 3-phase electrical system. What this means is that if you have a 30-amp EVSE at home like I do, it will charge faster than an identical unit located at a commercial building.

This is because single-phase service measures 240 volts between two hot leads and 120 volts between hot and neutral. In a commercial building with 3-phase service, the voltage between two hot leads is only 208 volts, but any hot to neutral is still 120 volts. No matter where you are in the US, level 1 will charge at the same rate for the same amperage. However, because level 2 EVSE are supplied with a lower voltage when fed from a 3-phase system, power into the car is lower for a given amperage when compared to level 2 charging at home.

The car always pulls the same current if allowed by the EVSE, but since the voltage is lower (208 instead of 240), total kW power is lower (Volts X Amps = Watts). So, a 12 amp charge looks like this:

208 X 12 = 2,496 Watts
240 X 12 = 2,880 Watts
120 X 12 = 1,440 Watts (for comparison to level 1)

What we also see from these calculations is that level 2, single-phase power is exactly double that of a level 1 charge, but (here's the important piece of information I think Don isn't factoring in) the car has a constant ~600 watt drain from the electronics when charging. When we factor that in:

208 X 12 = 2,496 Watts - 600 watt vampire = 1,896 Watts into battery pack
240 X 12 = 2,880 Watts - 600 watt vampire = 2,280 Watts into battery pack
120 X 12 = 1,440 Watts - 600 watt vampire = 840 Watts into battery pack

Now we see that single-phase level 2 has almost 3 times more power going into the battery pack compared to level 1. If I had numbers on cell efficiency for different power inputs, we might also find that the cells charge more efficiently at the higher rate, so effectively the pack does store usable energy 3 times faster than when plugged into level 1.

Now, a little fun fact. I charged at a friend's house once a couple years ago. He has an EVSE fed by a step-up transformer, which bumps up the voltage to about 250 volts. We plugged it into my i-MiEV and watched what happened on CaniOn. What we saw was, with 250 volts feeding the car, we hit the max power input of the onboard charger and the amperage dropped. I believe 2.6 kW was the max power going into the pack.

 

[coulomb]

... the car has a constant ~600 watt drain from the electronics when charging.

Is that from air conditioning, or mainly the DC-DC charging the auxiliary (12 V) battery at some 40 A, running fans and so on as well?

600 watts is a lot to lose merely in charger losses, and many of the charger losses are proportional to the square of the charge current (I²R losses), not constant losses.

 

[coulomb]

He has an EVSE fed by a step-up transformer, which bumps up the voltage to about 250 volts.

An actual step-up transformer capable of 2.6 kW would be quite large and heavy, not to mention expensive. I assume it was actually an auto-transformer, boosting from 240 to 250 V?

Still, it's an interesting observation. More voltage only helps up to a point, that point being where the total power limit is reached.

 

[PV1]

It was a rather small transformer, so I may have used the wrong description.

As for vampire loads in the car, there is quite a bit. There are at least 2 contactors engaged, there are losses in the charger, the coolant pump cycles on and off, the main computers are all active, and (although negligible) the charge gauge and plug light are lit on the instrument cluster. Nearly all of these components are powered through the 12 volt system, so they all incur losses in the DC-DC converter (not to mention an amp draw by the 12 volt battery itself).

 

[Don]

What we also see from these calculations is that level 2, single-phase power is exactly double that of a level 1 charge, but (here's the important piece of information I think Don isn't factoring in) the car has a constant ~600 watt drain from the electronics when charging.

You're right - I always knew that L2 was some number more efficient than L1, both because L1 @ 12 amps can't get to 50% of the max power the charger can deliver and because it halves (or more) the time that the ancillary drain is present - Did not realize however that it was as high as 600 watts, nor that it was a continuous 600 watts. I would have guessed (without running the numbers) that L2 charges about 2.5 times as fast as L1, but it looks like the real number is much closer to 3X than I thought

I assumed (bad thing to do I know) that the current drawn by the DC to DC converter would eventually reduce somewhat as the 12 volt battery gets to a full charge, so with L1, that inefficiency would eventually taper off, but it appears not, since the 600 watts appear to be constant

Moot point now (at least for me) as it's unlikely I'll be recharging at L2 speeds ever again, now that we know how blazing HOT the charger gets and how poorly it's cooling system functions

Don