OK to use 3-prong 'medium duty' digital timer with EVSE as Leaf 'S' timer? Bad idea? Overheating? OK if gets just warm?

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ldallan

Well-known member
Joined
Jan 16, 2017
Messages
52
Location
Colorado Springs, CO
[Sorry if this has been asked before]

I've got a "Defiant Heavy Duty Timer" from Home Depot. SKU 457-864:
https://www.homedepot.com/p/Defiant-15-Amp-7-Day-Indoor-Plug-In-Digital-Timer-with-2-Grounded-Outlets-White-49808/203678095
Defiant model: GE5374-71L3
125 VAC 60 hz
15a General Purpose/Resistive
125 VAC 60 hz 1/2 HP
Made in China

With my 2015 Nissan Leaf 'S' without TechPackage and without CarWings/NissanConnect, I've found the built-in timer to be difficult to use. It can be more trouble than the hassle is worth.

I'm considering using a three-prong digital timer. It's described on the package/web-site as "Heavy Duty", but this non-electrician thinks of it as "Medium Duty". To me, two-prongs without ground would be "Light Duty".

We’re retired without a commute. Each day is different. I want to avoid charging past 90%.

The timer would go into the 110v outlet in the garage; the EVSE would plug into that; and then plug into the Leaf J-1772 connector. I wouldn’t be using the “7 Day Programmability” feature.

What could go wrong? ;-(

Rather than cross my fingers, I thought I'd check first with this forum. Do one or more of the following apply?

  • Flawed idea. Don't even try.
  • BAD IDEA!!! We're sending the fire department in advance of need.
  • Could be hard on the EVSE?
  • Should work fine, as that is something the person making the reply does.
  • Proceed Cautiously: OK if timer gets slightly warm? Also check EVSE.
  • Flawed if timer gets noticeably warm ... but can be reasonably tolerated
  • Dangerous if very warm / hot.
  • Maybe try it with a 1500 watt hair dryer first?
 
Theoretically, it should be fine. The Nissan-supplied L1 EVSE for your car is limited to 12A so it is within the 15A limit of the timer. I would also call the Leaf charge port a 'resistive' load since the on-board charger shouldn't have a large inductance (like a large motor could). So this use should be within the stated specs on the part. Worst case of course would be the unit catches fire or explodes. Probability of that depends on how well it is designed and manufactured. In this day and age I think the chances of that would be slim.

I would be just as concerned with multiple insertion cycles of the plugs so I would recommend just leaving it installed semi-permanently rather than plugging and un-plugging it often.
 
ldallan said:
  • Flawed idea. Don't even try.
  • BAD IDEA!!! We're sending the fire department in advance of need.
  • Could be hard on the EVSE?
  • Should work fine, as that is something the person making the reply does.
  • Proceed Cautiously: OK if timer gets slightly warm? Also check EVSE.
  • Flawed if timer gets noticeably warm ... but can be reasonably tolerated
  • Dangerous if very warm / hot.
  • Maybe try it with a 1500 watt hair dryer first?

Not recommended. When the timer shuts off, the car will be drawing full current, and is going to be somewhat of an inductive load, so there will be arcing on the contacts. So your timer's life is shortened. Not good. Also, disconnecting the power is not the recommended way to shutdown the car's charger. Would be better if the charger could shutdown the current gracefully. But the charger very probably will survive this.

What you want would be an EVSE that shuts off the pilot signal, same as what happens when you unlatch the cable from the car. Low voltage, low current, tells the charger in the car to shutdown and draw no current...
 
what exactly about the LEAF charger timer is so difficult? You also really should investigate 240 volt charging options. This increases your efficiency 250% over 120 volts and is much easier to calculate charging times.
 
goldbrick said:
Theoretically, it should be fine. The Nissan-supplied L1 EVSE for your car is limited to 12A so it is within the 15A limit of the timer. I would also call the Leaf charge port a 'resistive' load since the on-board charger shouldn't have a large inductance (like a large motor could). So this use should be within the stated specs on the part. Worst case of course would be the unit catches fire or explodes. Probability of that depends on how well it is designed and manufactured. In this day and age I think the chances of that would be slim.
Interesting. Thanks.

I would be just as concerned with multiple insertion cycles of the plugs so I would recommend just leaving it installed semi-permanently rather than plugging and un-plugging it often.
Good point. I hadn't really thought this half-baked idea through.
 
DaveinOlyWA said:
what exactly about the LEAF charger timer is so difficult?
On the 'S' model, my evaluation is that the built-in timer is primitive, non-intuitive, and problematic. I can expand on that.

I've used the 'S' timer about 20 or more times at free Level-2 stations at both Nissan dealers and our local utilities that has a public, free pair of charging heads. I was able to get it to work semi-reliably, but it took a pencil, paper, clipboard, and calculator. I can be slow ... my bad.

I have used the 'S' timer at 3 different ChargePoint free chargers, including several times before I got their smart-phone app. Other than being kludgy and with lots of room for improvement, I really like using the ChargePoint app. (I've submitted 3 Feature Requests.) Once, I figured out the ChargePoint app, the 'S' timer is moot.

Do you use the timer capability? On what model? 'S'? I speculate you've owned several Leafs.

You also really should investigate 240 volt charging options.
Good point. I have. However, for our (eccentric?) "use case", a home Level-2 doesn't make economic sense.

This increases your efficiency 250% over 120 volts and is much easier to calculate charging times.
We may have a different understanding of efficiency. WRT wall-clock time?

FWIW:
My impression is that Level-2 may be more efficient than Level-1 in terms of losses ... how much of 10 kwh from the "wall" actually gets into the Leaf battery. Maybe one has 10% losses and the other has 15% losses?
 
WetEV said:
Not recommended. When the timer shuts off, the car will be drawing full current, and is going to be somewhat of an inductive load, so there will be arcing on the contacts. So your timer's life is shortened. Not good. Also, disconnecting the power is not the recommended way to shutdown the car's charger. Would be better if the charger could shutdown the current gracefully. But the charger very probably will survive this.
To my shame, most of that is over my head. I've got an engineering background (mech, industrial, software), but my brain doesn't seem to be wired to have more than a jr. high level of comprehension of electricity.

What you want would be an EVSE that shuts off the pilot signal, same as what happens when you unlatch the cable from the car. Low voltage, low current, tells the charger in the car to shutdown and draw no current...
Interesting.

In reflecting on the good replies I've gotten (thx!), I'm coming around to the realization that with slow Level-1 charging at home, the degree of timing precision really doesn't matter.
 
ldallan said:
DaveinOlyWA said:
what exactly about the LEAF charger timer is so difficult?
On the 'S' model, my evaluation is that the built-in timer is primitive, non-intuitive, and problematic. I can expand on that.

I've used the 'S' timer about 20 or more times at free Level-2 stations at both Nissan dealers and our local utilities that has a public, free pair of charging heads. I was able to get it to work semi-reliably, but it took a pencil, paper, clipboard, and calculator. I can be slow ... my bad.

I have used the 'S' timer at 3 different ChargePoint free chargers, including several times before I got their smart-phone app. Other than being kludgy and with lots of room for improvement, I really like using the ChargePoint app. (I've submitted 3 Feature Requests.) Once, I figured out the ChargePoint app, the 'S' timer is moot.

Do you use the timer capability? On what model? 'S'? I speculate you've owned several Leafs.

You also really should investigate 240 volt charging options.
Good point. I have. However, for our (eccentric?) "use case", a home Level-2 doesn't make economic sense.

This increases your efficiency 250% over 120 volts and is much easier to calculate charging times.
We may have a different understanding of efficiency. WRT wall-clock time?

FWIW:
My impression is that Level-2 may be more efficient than Level-1 in terms of losses ... how much of 10 kwh from the "wall" actually gets into the Leaf battery. Maybe one has 10% losses and the other has 15% losses?


amount of power from wall that does not get to your battery on 120 volts@ 12 amps; 25% . 240 volts@ 27.5 amps (or thereabouts); 10%.

I do not use timer. With 240 volts and a light driving demand, I can usually get what I need in 2 hours or less. IOW, if I need to, I plug it in when I get up in the morning and its ready to go by the time I leave for work.

But that is the advantage of 240 volts over 120 volts. You likely don't have to do much more than setting your timer to charge for two hours on 240. On 120, its now 7 hours or more.
 
WetEV said:
Not recommended. When the timer shuts off, the car will be drawing full current, and is going to be somewhat of an inductive load, so there will be arcing on the contacts. So your timer's life is shortened. Not good.

I thought of this too but I don't know if the timer has mechanical contacts or uses solid state switches. Without opening it up it's hard to tell but if it's rated for 15A then switching 12A should work. And in my extremely limited experience with this sort of thing I would still call the load resistive instead of inductive although that is a qualitative statement and I don't know the actual impedance characteristics of the on-board charger.

WetEV said:
Also, disconnecting the power is not the recommended way to shutdown the car's charger. Would be better if the charger could shutdown the current gracefully. But the charger very probably will survive this.

What you want would be an EVSE that shuts off the pilot signal, same as what happens when you unlatch the cable from the car. Low voltage, low current, tells the charger in the car to shutdown and draw no current...

Totally agree but once again it would be good to know how the switch operates. If it is solid state it may actually ramp the current down gradually. If it's just mechanical contacts then I'd be more worried. But then any normal light switch uses mechanical contacts and they seem to last a long time with all kinds of various loads being switched on/off.
 
Hi Idallan,

Why not just skip using a timer? When it's low (under 40%), set it for immediate charging and plug it in early in the morning. Then if you unplug before you go to bed you'll be close to 90%. And if you forget, charging to 100% periodically is not bad.

Ron
 
I used a mechanical timer for about 8 months without problems when I first got the car... At 120 volts, the charger uses 12amps, and a timer is rated at 15 amps. No problem. . I used to set the timer for 5 % battery charge per every 1 hour of charging. So 10 hours of charging overnight gave me 50% increase in battery capacity. If you do not need the car in the evenings, or drive short distances (10-20 miles/ day), you can get away with the standard 120 volt level 1 charger.

If you want to have more flexibility, and willing to get an electrician to put in a 240 volt line, that is the way to go. you can easily calculate how much you are putting into the car because it takes such a shorter amount of time.... With the 240volt Level 2 charger, you charge at 30-35% charge per hour (or 1% of charge for every 2 minutes of charging). So if I want to only put 20% more into the battery, I plug it in, set a timer for 40 minutes (or eat dinner), and then come out and disconnect.

It is also great with the 240 volts that you can have your car at 100% with only a short amount of charging at any time of the day or night (24/7). For me, that is the way to go... Use the entire capacity of the car....
 
goldbrick said:
Totally agree but once again it would be good to know how the switch operates. If it is solid state it may actually ramp the current down gradually. If it's just mechanical contacts then I'd be more worried. But then any normal light switch uses mechanical contacts and they seem to last a long time with all kinds of various loads being switched on/off.

So let's look at a switch with different loads.

https://www.homedepot.com/p/Intermatic-15-Amp-In-Wall-Heavy-Duty-Astronomic-Digital-Timer-EI600WC/203954897?MERCH=REC-_-PIPHorizontal1_rr-_-206365454-_-203954897-_-N

Resistive (heater): 20 Amp, 120-277 VAC
Tungsten (incandescent): 15 Amp, 120 VAC; 6 Amp, 208-277 VAC
Ballast (magnetic): 16 Amp, 120-277 VAC
Motor: 1HP, 120 VAC; 2 HP, 240 VAC
DC Loads: 4 Amp, 12 VDC; 2 Amp, 28 VDC

The charger in the car isn't similar to any of these.

Notice that the range of current that can be supported ranges from 20 Amps for a pure resistance to 2 Amps for 28 VDC. Strange and wonderful things can and do happen with loads that are not simple resistive.

Motor of 1 hp draws 745 watts (assuming 100% efficiency, and ignoring startup currents, inductance and capacitance), or 6.2 Amps. Efficiency is usually fairly high, 90% or so, so why can this switch only support ~7 Amps for a motor? Oh, all the things I just ignored. During startup the current is rather larger, perhaps even rather more than the 20 Amp steady state limit, but as the duration is likely short time is usually not a problem.

Have an ohm meter? Measure an incandescent bulb's cold resistance. Calculate the startup current. Sure, a huge current, over ten times the steady state current, and it just flows for a tiny time until the filament is hot. That is probably why the above switch is rated for a lower current, 15 Amps of incandescent load, than for 20 Amps of resistive load.

Will using a timer work? Probably. Still, isn't a good idea. Not recommended. Suggest getting an EVSE, perhaps an EVSE with a timer.
 
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