charging efficiency

[rkshack]

First off, you are not charging from zero to 24 kWh. Nissan has limited user access to only a percentage of the full pack capacity. Most of us accept the estimate that user available capacity is 21 to 21.5 kWh.

Owners who have charged at 240 Volts to "full" 100% charge from "turtle" (which is as empty as the car will allow you to get) in new cars with full battery capacity have reported using about 25 kWh from the power panel, as I recall. I think that I used 26.2 kWh, but my reading was considered an outlier.

So in estimating the cost of charging the battery from turtle to full I would do ~21kwh and then add 300 watts per hour because I am using 120v charging. So if it took me 21 hours I would get about 27.3 kwh to charge the batter. Is my logic correct?

rkshack

 

[planet4ever]

So in estimating the cost of charging the battery from turtle to full I would do ~21kwh and then add 300 watts per hour because I am using 120v charging. So if it took me 21 hours I would get about 27.3 kwh to charge the batter. Is my logic correct?

You are getting there, but there is another factor. The 300 watts covers auxiliary use, like running the cooling system that keeps the charger cool, and the computers that control everything. But why does the cooling system have to be running? That's because the charger generates heat, and that means it is less than 100% efficient. I'm no expert, but I think I have seen numbers thrown around like 90% efficiency in the charger itself.

Ray

 

[rkshack]

I was thinking of using a kill-a-watt to measure the out watts used so I could get an idea of my actual costs.

The plug I use already has a refrigerator on it and so the kill-a-watt won't fit. If I got a heavy duty extension cord or a small plug extender would that work. The problem is the kill-a-watt blocks the both plugs when it is plugged in an unplugging the fridge is really not an option.

Thanks
rkshack

 

[essaunders]

I was thinking of using a kill-a-watt to measure the out watts used so I could get an idea of my actual costs.

The plug I use already has a refrigerator on it and so the kill-a-watt won't fit. If I got a heavy duty extension cord or a small plug extender would that work. The problem is the kill-a-watt blocks the both plugs when it is plugged in an unplugging the fridge is really not an option.

Thanks
rkshack

You really want a dedicated outlet for charging. Even (especially?) for 120v.

 

[rkshack]

I was thinking of using a kill-a-watt to measure the out watts used so I could get an idea of my actual costs.

The plug I use already has a refrigerator on it and so the kill-a-watt won't fit. If I got a heavy duty extension cord or a small plug extender would that work. The problem is the kill-a-watt blocks the both plugs when it is plugged in an unplugging the fridge is really not an option.

Thanks
rkshack

You really want a dedicated outlet for charging. Even (especially?) for 120v.

I only have one plug in the garage and the freezer is on it. What happens if they are both plugged into it?

Will my extension idea for the kill-a-watt work?

rkshack

 

[dgpcolorado]

You really want a dedicated outlet for charging. Even (especially?) for 120v.

I only have one plug in the garage and the freezer is on it. What happens if they are both plugged into it?

Will my extension idea for the kill-a-watt work?

rkshack

If both the EVSE and freezer are on at the same time the circuit breaker may trip. The L1 EVSE draws 12 Amps, which is the most that a standard 15 Amp household circuit should be used for (80% of rated capacity). As essaunders said, you really need a dedicated circuit for an EVSE. And the wiring should be in good condition. Any outlet that is not part of a circuit used by another device, such as your freezer, should suffice. If you only have one circuit in your garage (that's unusual in my experience) you need to add another, complete with an additional 15 Amp breaker in your electrical panel. (And if you need to add another circuit you might want to consider using heavier wiring so that you can upgrade it to 240 Volts someday.)

 

[ebill3]

For several months before I upgraded my EVSE, I charged L1 from the same 15 Amp socket as a small chest freezer. No problems, no heat. OTOH, the Kill A Watt with a short extension cord did not like a constant 12 Amps, and got hot enough to de-solder one of the prongs from the PCB.

 

[rkshack]

For several months before I upgraded my EVSE, I charged L1 from the same 15 Amp socket as a small chest freezer. No problems, no heat. OTOH, the Kill A Watt with a short extension cord did not like a constant 12 Amps, and got hot enough to de-solder one of the prongs from the PCB.

what is the pcb. Was the short extension a heavy gauge?

Is the only risk a flipped breaker. I have had the car for a few weeks and have not had a problem yet.

Rkshack

 

[gbarry42]

The PCB is the printed circuit board inside the Kill-A-Watt. Wire size is important, but a lot of overheating problems occur at the connectors. Any resistance there, and you will get a hot spot. And, heat makes the resistance go up, so the problem just gets worse until it melts, burns through, or starts a fire.

 

[rkshack]

So if I plug in a kill-a-watt directly into the wall do I have to worry about the pcb catching on fire.

Rkshack

 

[DaveinOlyWA]

I used the kill a watt for3 years on my zenn and5 months on my Leaf all at 12 amps and had no issues

 

[dgpcolorado]

I used the kill a watt for3 years on my zenn and5 months on my Leaf all at 12 amps and had no issues

I've also used mine for extended L1 charges with no issues. But Phil has reported that the quality of manufacture of the Kill-a-Watt meters is uneven and some can overheat under prolonged 12 Amp use. I guess it is luck of the draw as to whether or not one gets a good one, as it appears you and I did.

 

[Nubo]

I like having 2 units for a couple of reasons. One, it lets me keep the Nissan-supplied unit in the car at all times, for emergencies. Two, if my wall-mount unit (or its 240V circuit or breaker) should ever have a problem, I've got a fully functional spare ready to go and capable of charging off a 120V circuit.

 

[rkshack]

I used the kill a watt for3 years on my zenn and5 months on my Leaf all at 12 amps and had no issues

I've also used mine for extended L1 charges with no issues. But Phil has reported that the quality of manufacture of the Kill-a-Watt meters is uneven and some can overheat under prolonged 12 Amp use. I guess it is luck of the draw as to whether or not one gets a good one, as it appears you and I did.

Is there any risk, other than hurting the kill-a-watt. Any chance of damaging the cable or the car? Also can you feel that is starting to have problems because it gets hot?

Rkshack

 

[DaveinOlyWA]

I used the kill a watt for3 years on my zenn and5 months on my Leaf all at 12 amps and had no issues

I've also used mine for extended L1 charges with no issues. But Phil has reported that the quality of manufacture of the Kill-a-Watt meters is uneven and some can overheat under prolonged 12 Amp use. I guess it is luck of the draw as to whether or not one gets a good one, as it appears you and I did.

Is there any risk, other than hurting the kill-a-watt. Any chance of damaging the cable or the car? Also can you feel that is starting to have problems because it gets hot?

Rkshack

no. and lets face it, for the price of a replacement EVSE, it should protect the car 100% without fail and that is exactly what it is designed to do.

on my Kill a watt, even when charging the Zenn it drew over 11.5 Amps (Zenn was not a well thought out design and i saw rates up to slightly over 12 amps frequently but usually only for about 10-15 minutes which is probably the reason batteries did not last) , which is only slightly less than what the Leaf drew. but only for 2-3 hours before it started winding down. mine never got warm, i unplugged it daily after taking Kwh readings. i plugged the charge cord into it daily when using it with Zenn (did not unplug EVSE from kill a watt much with Leaf since i rarely took cord with me)

now i bought my Kill a watt at Amazon and they had literally a half dozen different kinds that all seemed to be about the same but thinking that there were other brand names involved?

 

[dgpcolorado]

Is there any risk, other than hurting the kill-a-watt. Any chance of damaging the cable or the car? Also can you feel that is starting to have problems because it gets hot?

Rkshack

I suppose that a melting Kill-a-watt meter could catch fire or damage the plug on the end of the EVSE. More likely it would just open the circuit and shut things off. It wouldn't hurt the car. If you use a Kill-a-watt meter for an hour or so with a 12 Amp load and it doesn't heat up, I wouldn't worry about it.

My concern about not using a dedicated circuit for the EVSE is that it could become overloaded. If the house wiring is not in good condition it could overheat. The idea that one should draw no more than 80% of the breaker/circuit rating is a safety factor. Sure you can draw 14 Amps and the breaker shouldn't trip and the wiring shouldn't overheat if it was properly installed and in good condition. But that doesn't mean that it is a good idea.

It has been suggested in other threads that you can check the condition of your circuit by measuring voltage with the EVSE on (LEAF charging) and off (no loads). If the voltage is more than a few percent different the circuit wiring might not be up to snuff. I'm not an EE so I can't be more specific than that (but there are plenty of EEs here who can explain it better).

 

[DaveEV]

So if I plug in a kill-a-watt directly into the wall do I have to worry about the pcb catching on fire.

You should watch it carefully - I opened one up and it's obviously not designed to handle high current for long periods of time.