maximum charging rate for 120V?

jasleinstein · Sep 12, 2014

Has anyone actually measured maximum 120v charging rate? Has anyone verified a rate of 1.9 kW? Due to the charging issue of the KLE I may be forced to charge on 110v as my other EV and the BMW need to share charge time, and they can't both get done on 220v in my charge window time. I need every kw possible to use 120v.

I was on the phone today with Clipper Creek wanting to order the HCS-20 charger. They told me they thought the i3 would only charge at 1.4 kW on 120v. I have a 25 amp dedicated circuit but don't want to waste money of the car won't charge at the higher rate. I hear BMW say the car "might" charge at a higher rate, but frankly after the KLE software setback and incorrect statements " In some cases the charging rate may be reduced by up to 30%" when in fact it all charging is capped at 5kW, I am a bit gun shy.

Has anyone actually measured maximum charging rate on 120V?

thanks

This text was used as a response in another thread, so I apologize.

KurtEndress · Sep 13, 2014

I'll repeat some of what I said in the other thread.

Last night I recharged my i3 REx from 58% in 8.5 hours. That works out to about 5% per hour or 930 watts into the battery.

The L1 high setting is 12A, so it can draw about 1440 watts from the wall, but that's not what makes it into the battery.

mindmachine · Sep 13, 2014

KurtEndress said:
I'll repeat some of what I said in the other thread.

Last night I recharged my i3 REx from 58% in 8.5 hours. That works out to about 5% per hour or 930 watts into the battery.

The L1 high setting is 12A, so it can draw about 1440 watts from the wall, but that's not what makes it into the battery.

I have both the i3 and a 2014 Prius plugin and while I don't use 120 volt charging on the i3 I do on the Prius. I am not 100% sure weather the Prius EVSE should provide 10 or 12 amps, but the Prius reports how many kwh it is drawing and it only draws 900 watts. 920/1.2 kwh input assuming 10 amp capability would be 77% efficiency.

KurtEndress · Sep 13, 2014

mindmachine said:
I have both the i3 and a 2014 Prius plugin and while I don't use 120 volt charging on the i3 I do on the Prius. I am not 100% sure weather the Prius EVSE should provide 10 or 12 amps, but the Prius reports how many kwh it is drawing and it only draws 900 watts. 920/1.2 kwh input assuming 10 amp capability would be 77% efficiency.

Your Prius drawing 900 watts is different from 900 watts going into the battery. There are losses at various stages, but converting AC from the wall to DC for the battery is probably the biggest. What is the Prius reporting? Making assumptions about how much it draws from the wall makes the 77% efficiency figure a pure guess.

My I3 reported I drove 37.3 miles at 4.7 mi/kWh consumption. That works out to 7.94 kWh used. It said the SOC was 58% which means 7.90 kWh missing from the battery. So the car is consistent within the two digit precision of the figures.

I have a TED monitor that showed about 1400 watts extra flowing through my electrical panel for 8.5 hours (plus or minus 5 or 10 minutes). From that I calculate about 66% efficiency for the combined wiring loss, charger loss and battery loss. That's close to a wall to wheels figure except that it also includes the 120V wiring to the garage and a heavy duty extension cord. I only have a 15A circuit in the garage so that may use just 14 gauge wire which will definitely add to the loss with a 1400 watt draw. The 25 ft 12 gauge extension cord is less of a problem than the house wiring.

I'm currently working out the scheduling to have an electrician install a 40A 240V L2 EVSE for me. That will be a faster and more efficient way to charge. Though a 20% more efficient charge isn't going to pay off the L2 EVSE anytime soon since EV's are so inexpensive to run anyway.

mindmachine · Sep 13, 2014

KurtEndress said:
mindmachine said:

I have both the i3 and a 2014 Prius plugin and while I don't use 120 volt charging on the i3 I do on the Prius. I am not 100% sure weather the Prius EVSE should provide 10 or 12 amps, but the Prius reports how many kwh it is drawing and it only draws 900 watts. 920/1.2 kwh input assuming 10 amp capability would be 77% efficiency.

Click to expand...

Your Prius drawing 900 watts is different from 900 watts going into the battery. There are losses at various stages, but converting AC from the wall to DC for the battery is probably the biggest. What is the Prius reporting? Making assumptions about how much it draws from the wall makes the 77% efficiency figure a pure guess.

My I3 reported I drove 37.3 miles at 4.7 mi/kWh consumption. That works out to 7.94 kWh used. It said the SOC was 58% which means 7.90 kWh missing from the battery. So the car is consistent within the two digit precision of the figures.

I have a TED monitor that showed about 1400 watts extra flowing through my electrical panel for 8.5 hours (plus or minus 5 or 10 minutes). From that I calculate about 66% efficiency for the combined wiring loss, charger loss and battery loss. That's close to a wall to wheels figure except that it also includes the 120V wiring to the garage and a heavy duty extension cord. I only have a 15A circuit in the garage so that may use just 14 gauge wire which will definitely add to the loss with a 1400 watt draw. The 25 ft 12 gauge extension cord is less of a problem than the house wiring.

I'm currently working out the scheduling to have an electrician install a 40A 240V L2 EVSE for me. That will be a faster and more efficient way to charge. Though a 20% more efficient charge isn't going to pay off the L2 EVSE anytime soon since EV's are so inexpensive to run anyway.

You are wrong, the Prius measures what is going into the battery and that is what i stated. Based on the time to charge the Prius from empty and the usable capacity of the battery I know it is reporting the kwh rate of charge that it is actually storing. But since you apparently know so much what is your question and reason for asking the same question in two different threads anyway? :roll:

jasleinstein · Sep 13, 2014

We got a little off base here. So the maximum charge rate for the i3 on 120v is 1.4kW right? It will not charge at 1.8 or 1.9 kW?

thanks guys!!

KurtEndress · Sep 13, 2014

jasleinstein said:
So the maximum charge rate for the i3 on 120v is 1.4kW right? It will not charge at 1.8 or 1.9 kW?

Yes, with the i3 120v occasional charger it will draw 12 Amp at maximum, or 1.44 kW. What goes into the battery will be less.

I don't kmnow if it is possible to do better on 120V with a differnet EVSE. From what I read the ESVE can signal over the J1772 connection that it is capable of 6, 12, 18, 24, or 30 amps. Maybe the i3 could handle 120V at 18A if the EVSE said it could do it. I seem to recall someone saying that their car was charging at 3 kW off a L2 EVSE and found that it had been installed incorrectly with only one hot lead connected; effectively just a 30A 120V circuit.

KurtEndress · Sep 13, 2014

mindmachine said:
You are wrong, the Prius measures what is going into the battery and that is what i stated. Based on the time to charge the Prius from empty and the usable capacity of the battery I know it is reporting the kwh rate of charge that it is actually storing. But since you apparently know so much what is your question and reason for asking the same question in two different threads anyway? :roll:

Wrong about what? I asked (once in this thread) what the Prius is reporting as I don't know much about the Prius. You clarified that the 900 watts is what is going into the battery, so question answered.

I admit I'm skeptical of an efficiency computed from one measurement and an assumption. I'd be interested in hearing what its measured draw from the wall is so its efficiency at 120V charging could be computed.

jasleinstein · Sep 13, 2014

KurtEndress,

Sorry I should have referred to my earlier post. I am trying to see if buying the Clipper Creek 1.9kW charger will help my charging rate.One of the folks at Clipper Creek thought the i3 would not charge at a rate over 1.4 kW on 120v, regardless of which EVSE was used. .

Has anyone measured a charging rate over 1.4 kW using 120 for their i3? If so what EVSE were you using? How did you measure it? I have both a TED 5000 and good old fashion digital Fluke ampmeter.

I just looked at my charge rate. I ran the batteries down to 15 miles. Using the EVSE that came with the car, plugged into a 20 amp 120 circuit it is scheduled to take 28 hours to charge the car. ugh.

thanks

mindmachine · Sep 14, 2014

jasleinstein said:
KurtEndress,

Sorry I should have referred to my earlier post. I am trying to see if buying the Clipper Creek 1.9kW charger will help my charging rate.One of the folks at Clipper Creek thought the i3 would not charge at a rate over 1.4 kW on 120v, regardless of which EVSE was used. .

Has anyone measured a charging rate over 1.4 kW using 120 for their i3? If so what EVSE were you using? How did you measure it? I have both a TED 5000 and good old fashion digital Fluke ampmeter.

I just looked at my charge rate. I ran the batteries down to 15 miles. Using the EVSE that came with the car, plugged into a 20 amp 120 circuit it is scheduled to take 28 hours to charge the car. ugh.

thanks

The quote below is from a email sent to me by the i genius about charging:

_____________________________________________________________________________________________________________________________________
"Finding the Charge Time for an EV
Amps * Volts = Watts (per hour)
This will be the rate of charge. Since the i3 has an 18.8 kWh battery capacity, we will then divide 18.8 by the rate of charge to get the number of hours it will take.
*Since the battery is measured in kilowatt-hours, we need to make sure we divide our answer in Watts by 1000 so we are using the same units.
So there are 3 settings for the charging rate in the car, which equate to 8 amps, 10 amps, or 12 amps. The voltage is constant at 120, and we just do the math from there.
So if the car is set to use all 12 amps for maximum charging rate, we can 120V * 12A, which equals 1440W (1.44 kW) per hour.
We know that EV charging as a whole has about 81% efficiency. So we'll multiply the watts per hour by the efficiency to get a more realistic rate of charge, which gives us 1.44 (.81) = 1.1664
The usable battery is 18.8 kWh, so 18.8 / 1.1664 = 16.12 hours to charge.
If they have their i3 set to charge at 8A, we do the same thing.
120V * 8A = 960W (.96 kW)
.96 (.81) = 0.7776
18.8 / .7776 = 24.177 hours"

Everything I have heard and found says the max draw for 120 charging is 12 amps max, but in the calculation the i genius did not take into account the slow down of the charging rate over that occurs during last 10 to 15 % to full! So the calculated 16.12 hrs will be longer! However the 28 hrs seems way too long unless something isn't working right.

Chrisn · Sep 14, 2014

I think the "end of charge slow down" might not be as pronounced with L1 charging. Looking at my chargepoint graph at L2, I go from steady 5.1kW (not >7kW, but that's another thread) until 55 minutes prior to charging being done. BUT: it spends 25 mins of this ramp down STILL ABOVE 1.4kW. So, very roughly, the L2 spends an hour charging at about half (on average-- falling steadily) nominal rate. So you need to add 30 mins to the "simplistic" calculated charge time (what "should" take 30 mins, takes an half because at half rate).

But, for Level 1, it only spends 30 mins in the "top off" mode, so charge estimate should be extended by only 15 mins-- which is basically a rounding error when the overall time is so long and other variables are at work (line voltage not exactly 120, ambient temp changes will drive cooling needs and overall efficiency, etc.).

Finally, the 81% number is complicated number-- not some known constant. I think overall efficiency is positively correlated with charge rate. Some of the electric "tax" on charging is relatively fixed in nature (or fixed + variable) like battery cooling / fans and the charging electronics being "on." So the length of charging itself extends the length of the charging (if you follow me). So basically, I think overall efficiency is < 81% at 8A, which likely explains your seemingly too long charging window.

KurtEndress · Sep 14, 2014

jasleinstein said:
Sorry I should have referred to my earlier post. I am trying to see if buying the Clipper Creek 1.9kW charger will help my charging rate.One of the folks at Clipper Creek thought the i3 would not charge at a rate over 1.4 kW on 120v, regardless of which EVSE was used. .

I can't help you there. I wasn't aware that Clipper Creek had that 1.9 kW 120V unit. I was under the impression that 120V charging was limited to 12A and 1.4 kW, but that was probably an assumption. It would be interesting to hear if the i3 can go above 12A on 120V.

I don't see why it couldn't since it can handle up to 30A on 240V. I believe it splits 240V the charging between the KLE and EME with each handling 3.7 kW. The High-Voltage Components document says this on page 113:

"The EME is designed so it can provide a maximum electrical power of 3.7 kW on the output side. This is charging configuration is used (in the US market) only when charging with the occasional use cable via a household 120V socket. And it sufficient to fully charge the I01 high-voltage battery under optimal marginal conditions in about 16 hours."

lturcotte · Sep 15, 2014

Hi

I have an Evduty adapter, that can charge at 30A on 240 V
But when the electrician installed the unit, there was a wiring error and it was connected on 120 V instead of 240 V

Even if this is not part of the specification for the adapter, it was working.
the I3 was charging at about half the rate. ( around 7 hours for a full recharge )
I did not measure the current, but I would say it was charging close to 25 Amp @ 120V

Note: the adapter is on a seperate 40 Amp breaker.
On a 15 Amp breaker, you are limited to 12 Amp

KurtEndress · Sep 15, 2014

lturcotte, I thought I remembered that happening to someone. You have unintentionally confirmed that an i3 can charge at greater than 12A on 120V. Since the OP has a 25A 120V circuit he should be able to use the Clipper Creek ACS-20 to charge at 16A, 1.9 kW. That should be 25% faster than the standard 12A from the included occasional charger.

jasleinstein · Sep 16, 2014

To update my own post. I heard back from BMW concierge group today with the official data from BMW. The i3 will charge at a maximum rate of 12 amps / 1.4 kW on 120volts.
So buying the Clipper Creek ACS-20 for 16A, 1.9 kW charging would be a waste of money for the i3.

jadnashuanh · Sep 16, 2014

Keep in mind that the rate of charge is determined by two things, and the car sets what it wants based on its programming, and what the EVSE says is available. The car will never ask for more than the EVSE announces in its pilot signal, and at least in the USA, the i3 will not ask for more than 12A when facing 120vac, nor more than 30A at 240vac (note, the way things are rated, in Europe, a 32A unit will produce the same charge current as an SAE (US) 30A unit). Since 120vac isn't generally available in Europe, and in the USA, most branch circuits are only 15A on 120vac, with the code requirement of an 80% max load, for 12A, you'd need a 15A circuit...and, the power is going through a different branch in the car, and that may also limit the max charge rate in the current design of the KLE module at 120vac input.

Just like a 40-50A-or larger EVSE will work fine with the i3, at least as currently delivered, it will be no faster than one rated at 30A since, at 240vac, that's all the car is designed to utilize.

TonyWilliams · Sep 18, 2014

With a pilot signal at or above the maximum rate that the EV can accept, most modern EVSE's and EV's delineate at about 160 volts as L1 (below 160 volts) or L2 (above 160 volts).

While I have never tested a BMW i3, a Nissan LEAF will take the full amperage available at all voltages. The early Tesla products (excluding Roadster) like Model S, Toyota Rav4 EV and likely Mercedes B-Class ED will limit 20 amps on L1 and 40 amps on L2.

Later Tesla firmware updates in the past year have increased L1 to 24 amps.

jadnashuanh · Sep 18, 2014

The basic specifications for the i3 say the onboard charging system maxes out at 7400W. Somewhere between 30-32A, depending on the supplied input voltage. Regardless of what's available, the i3 can't use more than that.

TonyWilliams · Sep 18, 2014

jadnashuanh said:
The basic specifications for the i3 say the onboard charging system maxes out at 7400W. Somewhere between 30-32A, depending on the supplied input voltage. Regardless of what's available, the i3 can't use more than that.

Uh, I think that's known (and superseded by a lower charge rate from BMW after numerous onboard charger failures from overheating).

It doesn't address the question of amperage @ 120 volts.

beachfitrob · Mar 29, 2015

I have a 20A capable 110/220V EVSE. I just got my i3 REX tonight but I have owned a Chademo Leaf for about 14 months. At some point I'll compare/contrast on my blog. I have a Bluetooth OBD II, now to see what I can see.

maximum charging rate for 120V?

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