Fast Low Cost Charging - All EVSE Questions Answered!

[davewill]

Modded EVSE to the rescue! As some may know, I'm being the guinea pig for moving within the EV Project. Well, I had the circuit run at the new house only to have the city inspector tell me that the Blink had to be mounted at the new residence before he could pass the job and SDG&E could set their second meter. The problem being that I'm USING that Blink to charge my car at the old place. Luckily, I have my Rev 2 available to take up the slack, so no sweat!

 

[supergrump]

Is it less expensive to use 2 separate 120's as opposed to 1 240 outlet for charging. What is the time difference in charging, using the 12 amp system as opposed to the upgraded 16 amp system. What is the cost difference between the 2

 

[garygid]

The 12A 120v is around 20 hours.
The 12A 240v is about twice as fast, about 10 hours,

The 16A 240v version is about 30% faster than 12A 240v, so about 7.5 hours.

Using 240v "made" from two 120v (opposite phase) circuits is essentially the same as using a "real" 240v source. Of course, wiring rating and the associated Breakers might be different, so your max safe current might be different. Typical 240v sockets in the USA are rarely as low as 20 amps. Typical 120v sockets are only occasionally as much as 20 amps.

Drawing 80% of the Breaker rating (16 amps for a 20-amp Breaker and Circuit) is the max considered "safe" for "continuous" (over about 2 hours, I believe) loads.

Generally, it is believed that charging at 240v is somewhat more efficient than 120v, so the 240v charging should cost a little less.

Also, if you have TOD (Time of Day) billing for your electricity, the shorter charging time will better fit into the less costly Off-Peak billing periods. There can be a huge difference in cost if charging at Peak rates.

 

[Turbo3]

Correction, 120 volt charging is limited to 12 Amps. That is a Leaf charger limit and can not be changed by the EVSE even if it can supply 16 Amps.

 

[ebill3]

Is it less expensive to use 2 separate 120's as opposed to 1 240 outlet for charging.

If you are asking if one method uses more energy than the other, then no - same thing. If you are talking about equipment costs and installation, no way of telling without a lot more info.

Bill

 

[Volusiano]

Is it less expensive to use 2 separate 120's as opposed to 1 240 outlet for charging.

If you are asking if one method uses more energy than the other, then no - same thing. If you are talking about equipment costs and installation, no way of telling without a lot more info.

Bill

120V vs 240V use the same amount energy to charge the battery, BUT 240V charging should incur a little less energy loss due to inefficiency simply because of the charge time for 240V is less than that of the 120V.

 

[DaveinOlyWA]

the speed of the charge is important. with 120 volt 12 amp charging we see around a 75% efficiency due mostly to charging overhead from cooling the inverter and what not

240 volt 12 amp (EVSE mod) runs around 83% which i have tested and measured as with the 120 volt charging. now most report about 88% efficiency with the blink, aero's etc with 240 volt, 16 amp charging.

now when using two 120 volt 12 amp lines will have to guess it will be better than 1 120 volt line but not as good as the normal 16 amp 240 volt public L2 option

 

[planet4ever]

Is it less expensive to use 2 separate 120's as opposed to 1 240 outlet for charging.

If you are asking if one method uses more energy than the other, then no - same thing. If you are talking about equipment costs and installation, no way of telling without a lot more info.

120V vs 240V use the same amount energy to charge the battery, BUT 240V charging should incur a little less energy loss due to inefficiency simply because of the charge time for 240V is less than that of the 120V.

You are missing the point of the question, Volusiano. supergrump was asking about 2 separate 120's. i.e. he is thinking about a "Quick 220" type setup. In that context ebill3's answer is correct, and there is no issue of difference in charge time.

Ray

 

[Volusiano]

Is it less expensive to use 2 separate 120's as opposed to 1 240 outlet for charging.

120V vs 240V use the same amount energy to charge the battery, BUT 240V charging should incur a little less energy loss due to inefficiency simply because of the charge time for 240V is less than that of the 120V.

You are missing the point of the question, Volusiano. supergrump was asking about 2 separate 120's. i.e. he is thinking about a "Quick 220" type setup. In that context ebill3's answer is correct, and there is no issue of difference in charge time.

Ray

Oops, you're right. I missed the point. I thought that the OP was talking about the efficiency of charging for twice as long on 120v as opposed to half as long on 240V.

However, as an owner of the Quick220 myself, I can add that the standby power draw from the Quick220 is 8W. So if you use the Quick220 as a long term solution and don't want to keep plugging and unplugging it, then the difference between plugging the upgraded EVSE to 240V vs through a Quick220 is going to be the additional 8W while charging and the additional 8W also remains while not charging unless you put 2 switches on the 2 120V sources to switch them off. The Quick220 people also told me that if you switch off only 1 of the 2 120V sources, the standby power will go down from 8W to 2W.

 

[phxsmiley]

Has anyone tried using the 16A Rev2 evse upgrade with Quick220, but only with 15A outlets available?

I would like to upgrade to the Rev2, plan to use the Quick220, for charging at friends/family houses. However, I'm not sure of the availability of 2 20A outlets readily available in the friend's garage. In my garage, I only have 1 20A outlet, so it's definitely not guaranteed with houses around here. So, I'd hate to have all this 'ready to use', but be stuck only with 15A outlets available and have to go back to using 110V, 12A once I'm at my friend's house.

I'm curious if the 15A breakers would blow immediately, or is it close enough that it would work.

I would suspect that if it did work, we probably have a safety issue.

 

[Ingineer]

In every case, I've never had a 15a circuit trip when pulling 16a, as long as there was nothing else on the circuit. This includes several charging operations at a friend's 100 year old victorian apartment covered by only four 15a glass fuses.

In most cases even a 15A outlet (actually a sting of them) is actually covered by a 20A breaker.

Here is a typical NEMA breaker trip curve chart:

Note there is a little "padding" indefinitely, and even after that, you still have the orange tolerance band. This usually means at reasonable ambient temps you will have even more headroom.

-Phil

 

[phxsmiley]

Thanks, Phil, that chart really helps!

 

[smkettner]

I know 16a would help but I am fine with 12a 240v for the portable.

 

[ebill3]

I have two upgraded Nissan/Panasonic EVSEs and I elected to not have the EVSEs upgraded to 16 Amps. I have two home brew quick 240 volt boxes, and the one that is semi-permanently installed in my garage uses two 14 gage wire 15 Amp circuits, neither of which is dedicated to that purpose. One circuit also powers a small freezer and the other is used for residence lights. I rent and having a 240 volt circuit installed was not an option. I am comfortable with 12 Amps.

The second package travels in the LEAF, and who knows what circuit capacities you might encounter when using them. As a matter of fact, at one location I often use, one of the 120 volt circuits powers a freezer and the other powers a drink vending machine. So, 12 Amps works for me.

 

[Ingineer]

I have two upgraded Nissan/Panasonic EVSEs and I elected to not have the EVSEs upgraded to 16 Amps. I have two home brew quick 240 volt boxes, and the one that is semi-permanently installed in my garage uses two 14 gage wire 15 Amp circuits, neither of which is dedicated to that purpose. One circuit also powers a small freezer and the other is used for residence lights. I rent and having a 240 volt circuit installed was not an option. I am comfortable with 12 Amps.

The second package travels in the LEAF, and who knows what circuit capacities you might encounter when using them. As a matter of fact, at one location I often use, one of the 120 volt circuits powers a freezer and the other powers a drink vending machine. So, 12 Amps works for me.

Bill: The unit ALWAYS runs at only 12A when on 120V, the difference between Revision 1 and 2 is that when on 240V, the rev2 unit will run at 16A vs 12A for the rev1. The Rev2 unit is 25% faster.

Your scenario with the shared 120v outlets would be the same for either revision, as on 120v neither will pull over 12a.

-Phil

 

[greenleaf]

Interesting chart.

So at 2x rate current (e.g. 30A on a 15A breaker), it is still within spec for the break to trip only after 100s.

 

[Ingineer]

Interesting chart.

So at 2x rate current (e.g. 30A on a 15A breaker), it is still within spec for the break to trip only after 100s.

Most breakers use a thermal device to essentially model what's going on in the wire. So a small overload for a long time is tolerable, but a large overload for a short time is not. It's all about temperature rise, and this way circuits can handle large loads, such as motors starting, for brief periods without tripping their breakers.

-Phil

 

[ebill3]

I have two upgraded Nissan/Panasonic EVSEs and I elected to not have the EVSEs upgraded to 16 Amps. I have two home brew quick 240 volt boxes, and the one that is semi-permanently installed in my garage uses two 14 gage wire 15 Amp circuits, neither of which is dedicated to that purpose. One circuit also powers a small freezer and the other is used for residence lights. I rent and having a 240 volt circuit installed was not an option. I am comfortable with 12 Amps.

The second package travels in the LEAF, and who knows what circuit capacities you might encounter when using them. As a matter of fact, at one location I often use, one of the 120 volt circuits powers a freezer and the other powers a drink vending machine. So, 12 Amps works for me.

Bill: The unit ALWAYS runs at only 12A when on 120V, the difference between Revision 1 and 2 is that when on 240V, the rev2 unit will run at 16A vs 12A for the rev1. The Rev2 unit is 25% faster.

Your scenario with the shared 120v outlets would be the same for either revision, as on 120v neither will pull over 12a.

-Phil

I don't understand.

If I am using two 120 volt circuits in a quick 240 volt box, aren't I getting 240 volts just as if I took 240 volts reight out of the breaker box? If so, wouldn't the rev 2 EVSE draw 16 Amps from both 120 volt lines? :?:

Bill

 

[Ingineer]

I don't understand.

If I am using two 120 volt circuits in a quick 240 volt box, aren't I getting 240 volts just as if I took 240 volts reight out of the breaker box? If so, wouldn't the rev 2 EVSE draw 16 Amps from both 120 volt lines? :?:

Bill

Correct. If you use the Quick240 box, then you will be pulling 16A from each of the two 120v circuits on a Rev 2 or 12A on each from a Rev 1. If you don't use the Quick240 and plug straight into 120v though, it's always 12A regardless of whether you have Rev 1 or 2.

Sorry for the Confusion!

-Phil

 

[DaveEV]

Shipped my EVSE in yesterday for the upgrade - initially went for the standard upgrade (12A) but am now debating whether to go with the Rev2 16A.

Like ebill3 I plan on using a quick 240 type box on occasion when using it and am worried about tripping breakers unnecessarily if I can't find 2 dedicated 15A circuits.

I figure that charging at 240V/12A reliably is probably better than 240V/16A with the occasional circuit breaker trip!

But as Phil says 20A circuits w/15A outlets are not that uncommon and as the chart says one should be able to draw 16A continuous on a 15A circuit without tripping the breaker and possibly as much as 19A.

Any real-life experience with tripping breakers here? I suspect that many are simply plugging into regular 240V outlets and use of quick 240 type devices is fairly rare.

Would be nice if one could adjust charging current.