17A L1 charging!!

[lincomatic]

chris1howell lent me his DIY EVSE so I could debug my new firmware for it.

Last night, I was playing with the pilot duty cycle. I set it to 14A and plugged it into 120V.
My KillAWatt showed that it was drawing between about 13.2 and 13.9A. I ran it that way for over 1/2 hour.
This afternoon, I plugged it in again, this time with both the KillaWatt and a current clamp ammeter.
I heard some beeping while I was at the car, and realized that the KillaWatt was complaining of overcurrent.. it was also flashing its display.
It was reading 16.3A!! The current clamp reads about .5A higher, and it was reading 16.8A!
I unplugged the KillaWatt and used only the current clamp, and this time, it was drawing about 17.5A.
I only ran it for a couple of minutes before turning it off.
Very strange, because the pilot was still set to 14A.
There are two possible explanations factors that I can think of for the inconsistency: 1) it was extremely hot outside this afternoon... the car had been baking in the sun for several hours at 95F+ 2) our pilot is out of spec currently, because the op amp we're using is too slow. The J1172 spec wants a rise/fall time of 2us, and currently, we're way off at about 40us. But this still doesn't explain why I was able to consistently charge at around 14A on 2 different occasions spaced several hours apart.

I decided to wait until the outside temperature cooled off tonight. When I plugged it in, it charged at 15A this time.
Next, I bumped the pilot up to 16A, and the car drew 13A.
Next, I tried 15A, 18A, 14A in that sequence, and the car drew ~12A in all cases!
I tried 6A, and the car refused to charge.
I tried 10A, and the car drew about 8.5A.
Now, the car is charging ~12A again regardless of my settings at 14A,15A,16A.
Very inconsistent. I don't know how to explain it, except that maybe the car is getting confused by the slow rise time of my pilot.

I'm a bit disappointed .. I had visions of charging the car @ 16A on 120V.

 

[garygid]

Very inconsistant readings indeed.
Let us know what you find.

We had hoped that the LEAF would use 16A at 120v or 240v,
but Ingineer's tests concluded that the LEAF's charger was programmed for 12A max at 120v, and 16A max at 240v.

Is there anything strange about the 120v you are using, or the way the EVSE is wired to the car .... like the Neutral and Hot are reversed, or the Ground is "hot", and the LEAF is sensitive to that, and mistaking the input voltage for 240v instead of 120v?

Maybe the car measures Neutral to Ground, and assumes 240v if it measures 120v, and assumes 120v if it measures essentially zero?

OR, your ground wire to the car is floating, and the car is getting very confusing readings when trying to communicate to the grounded part of the car's electronics?

Just grasping at straws.

 

[lincomatic]

Logical guess, but I just rechecked the wiring, and I'm certain it's correct.
I haven't checked the wall socket, but I'm pretty sure that's OK too, because the Nissan EVSE is
very consistent at ~12A.

 

[chris1howell]

It would be really really hard to miswire the AC wires.

It would be great to charge at 120V 16A. I wonder if the voltage has high enough that the car thought it was > 120 and allowed the 16A mode.

 

[lincomatic]

It would be really really hard to miswire the AC wires.

It would be great to charge at 120V 16A. I wonder if the voltage has high enough that the car thought it was > 120 and allowed the 16A mode.

Good point. I'm going to try again this afternoon when it's nice & hot outside. This time, I'll monitor voltage as well.

 

[lincomatic]

OK it's not as hot as yesterday .. about 88. The open circuit voltage is 108.5V.

Here are my sequential tests:

capacity (A) charge current (A) charge volts (V)
15 14.433 98.6
16 14.55 97.9
17 14.5 98.2
18 14.69 97.7
20 14.6 96.5
12 11.47 100.1
13 11.97 99.7
15 14.7 96.4

The car had been charged to 80% last night. I didn't drive it at all but it stopped charging before 6AM when my timer cuts off.
So it looks like in warm weather, it sucks up to almost 15A. Maybe it only does it when the voltage drops?

 

[smkettner]

OCV 108? Charging voltage 96/100? Could it be drawing more amps due to the brown out conditions?

 

[lincomatic]

OCV 108? Charging voltage 96/100? Could it be drawing more amps due to the brown out conditions?

That's my suspicion. My house wiring isn't very good, and the EVSE is on a long 12ga extension cord.

 

[EVDRIVER]

OCV 108? Charging voltage 96/100? Could it be drawing more amps due to the brown out conditions?

That's my suspicion. My house wiring isn't very good, and the EVSE is on a long 12ga extension cord.

That and it may be cooling fan draw from the heat, are fans on? Your voltage is low.

 

[lincomatic]

That and it may be cooling fan draw from the heat, are fans on? Your voltage is low.

The fans didn't turn on. I think maybe smkettner is on to something. Maybe the Leaf doesn't impose a 12A limit but a limit in watts instead. 12A * 120V = 1440W. The amps/volts pairs I recorded above aren't accurate, because the values were fluctuating, and I had to switch the Killawatt between amps/volts modes to write down the values. But looking at my table, the combinations appear to yield ~1400W except for the 12 & 13A values, which are lower. The lower values for 12/13A could be due to the car reading my slow risetime pilot as the shorter duty cycles, which would result in it thinking that the current capacity is lower than what I programmed.
I wish I'd checked the voltage when it was pulling 17A. Right now I'm guessing that it was around 85V. On the other hand, it still doesn't explain why the car was exceeding the 14A pilot signal.

 

[lincomatic]

OK my line voltage just went up for a little while, and I now feel fairly confident that the car is trying to limit itself to 1440W instead of 12A.

When I plugged it in just now, it started with 13.8A/102.5V = 1415W.
After a while, the current increased to 14.1A and the voltage dropped to about 100.5 = 1417W

For more precision, I guess I should really be doing the tests reading off the watts, so see if that's relatively stable.

 

[smkettner]

If my house OCV was 108 I would be calling the electric company. I am at 121/124 volts.

 

[EVDRIVER]

That and it may be cooling fan draw from the heat, are fans on? Your voltage is low.

The fans didn't turn on. I think maybe smkettner is on to something. Maybe the Leaf doesn't impose a 12A limit but a limit in watts instead. 12A * 120V = 1440W. The amps/volts pairs I recorded above aren't accurate, because the values were fluctuating, and I had to switch the Killawatt between amps/volts modes to write down the values. But looking at my table, the combinations appear to yield ~1400W except for the 12 & 13A values, which are lower. The lower values for 12/13A could be due to the car reading my slow risetime pilot as the shorter duty cycles, which would result in it thinking that the current capacity is lower than what I programmed.
I wish I'd checked the voltage when it was pulling 17A. Right now I'm guessing that it was around 85V. On the other hand, it still doesn't explain why the car was exceeding the 14A pilot signal.

Have you read the tech specs in the service manual, there are thresholds listed for the charger for cut off, etc. There must be a voltage cut off that will impose a max amp draw by default.

 

[lincomatic]

Have you read the tech specs in the service manual, there are thresholds listed for the charger for cut off, etc. There must be a voltage cut off that will impose a max amp draw by default.

The voltage thresholds are only to determine the vehicle state ... unplugged/attached, not ready to charge/attached,ready to charge/ventilation required. The duty cycle of the pilot specifies the maximum current draw.

 

[garygid]

The AC power voltage is used to restrict/allow current flow as well as the Max-Current setting from the Control Pilot. A 120v AC Power source presumably uses only 12A, and 208v-240v should use a max of 16A.

Did you unplug the LEAF and re-start charging for each test? Or, did you just vary the CP pulse width DURING charging?

The EV SHOULD follow the CP Max-Current if the Max-Cur varies during charging. BUT, somebody reported that the LEAF does NOT follow, only uses what it first "reads" from the Control Pilot.

 

[lincomatic]

The AC power voltage is used to restrict/allow current flow as well as the Max-Current setting from the Control Pilot. A 120v AC Power source presumably uses only 12A, and 208v-240v should use a max of 16A.

Did you unplug the LEAF and re-start charging for each test? Or, did you just vary the CP pulse width DURING charging?

The EV SHOULD follow the CP Max-Current if the Max-Cur varies during charging. BUT, somebody reported that the LEAF does NOT follow, only uses what it first "reads" from the Control Pilot.

Right, I should have been more clear in the previous post. There are two different voltages here... AC voltage and pilot voltage.

The pilot is a +/-12V signal whose duty cycle is controlled by the EVSE in order to tell the car how many amps are available.
The EV then uses resistors to pull down the voltage to nominal values of 9/6/3V in order to signal back to the EVSE when to close the relays.

The AC voltage is also an input, which the car uses to decide what maximum current or power to accept, regardless of the number of amps that the pilot is advertising are available.

What I'm theorizing now is that the car limits not the current, but the power draw based on the AC voltage. So in brown out conditions, if the EVSE allows it, the car will draw more than 12A, up to its power limit for 120V.

120V * 12A = 1440W

So the limit for L1 charging is 1440W, not 12A.
I don't have a L2 yet, but I've heard the max for L2 is about 3.3KW or 13.75A @ 240V. I suspect if the voltage goes down, then the car will also draw more current as long as the EVSE sets its pilot to tell the car that more amps are available.

 

[lincomatic]

BTW, Edison is doing a bad job keeping the voltage up at my house. Yesterday, it floated up to 111V .. no higher, even after midnight.
But this morning, it's back to 119.5V.

So here's yet another reason to build a DIY EVSE ... so you can charge at full L1 power even when you're not getting a full 120V.
At the 96V I was getting yesterday, 96V * 12A = 1152W .. with the Nissan charger it charges ~300W slower.

 

[Randmac]

BTW, Edison is doing a bad job keeping the voltage up at my house.

A few years ago I was getting fluctuating voltage at my house when using a 120VAC window A/C unit. The circuit breaker supplying the A/C would trip even though the A/C load should not have been a problem and had been problem free for many years. After the breaker tripped I measured ~80VAC on the leg supplying the A/C circuit and 120VAC on the other leg at my service entrance. After 30 minutes or so the low voltage would creep back up to 120VAC.

Edison had done some line work behind my home a few months earlier and I assumed that something they changed had caused my problem. I called and Edison sent a service tech immediately. The tech pulled my meter and noted scorched contacts between the meter lugs and the meter socket on one leg. He did some other tests and determined that my service upstream of the meter was okay. He cleaned up and snugged up the damaged contacts as much as possible and re-installed the meter.

Everything downstream of the meter is my responsibility. The tech recommended I have the meter socket replaced and he even told me how I could reduce the cost by having a replacement socket on-hand for the electrican to install. It cost about 140 bucks parts and labor to repair a bad situation in my homes electrical service. Edision helped me after I let them know I was having problems.

 

[tps]

BTW, Edison is doing a bad job keeping the voltage up at my house. Yesterday, it floated up to 111V .. no higher, even after midnight.
But this morning, it's back to 119.5V.

Here in the Philly burbs at the office, our line voltage was low yesterday. 255V phase-to-neutral on the 480V 3-phase WYE feed from the utility as opposed to a nominal 277V, and after the step-down transformer, 105V as opposed to 117V. I concluded they must have been giving us a brown-out yesterday. Everything's back to normal today.

 

[wwhitney]

So the limit for L1 charging is 1440W, not 12A.

So perhaps the thread title should be changed to 17A charging at 85V?

Cheers, Wayne