5 Minute Cycle Timer to Charge Leaf - Is it safe?

[DaveinOlyWA]

I have looked everywhere (including this site) and do not see an answer to this problem.

I live in Juneau, AK. I am on a Peak rate. However, the peak rate is not a time-of-day rate. The peak rate is a useage peak rate where I am charges $10 per KW used in my highest 15 minute "peak" in a single billing cycle. In addition, I still have to pay for total KW in a billing cycle. Therefore, If I am charged $120 for my total KW in a single billing cycle, but my highest 15-minute peak is 15KW, my total bill would be (15KW x $10) = $150; plus the $120 total KW charge for a total bill of $270. Reduce the peak useage and I can greatly reduce my bill.

Clear as mud?

Anyway...

If I can cut my useage in half at night when charging my Nissan Leaf, I can cut my bill by about $80/month by reducing my peak useage during charging. My question is is it safe for a battery to have a frequent on/off cycle of 5-7 minute intervals? If so, I can charge a cycle timer. If not, I need to search for a lower amp L2 Charger.

I would prefer the cycle timer so I could override the charge in an emergency and during winter when peak use is not as much of an issue. Nov - Feb will always be high useage for me.

I drive a 2014 Leaf SV

it is perfectly safe to use a cycle timer or rather let me clarify.

Its "just as safe" as driving the car. If you have noticed, you constantly go from discharging to charging depending on driving conditions and at MUCH greater power than any home L2 will do so cycling every 5 mins or whatever is fine. You can also get a modified EVSE (or get your modified) that will allow an adjustable rate of charge. It is rare that one needs the full 6.6 KW rate for an overnight charge any way but the money spent (even $300 to modify) would be tough to justify.

I personally think you could easily charge at night without any increase to your bill at all. What is your current peak charge average per month now? you mention 15 KW which is a "bit" high. I would venture to think that you have something huge going on or that your usage overnight would normally drop significantly enough that your car could charge under your daytime peak.

 

[Oils4AsphaultOnly]

I have looked everywhere (including this site) and do not see an answer to this problem.

I live in Juneau, AK. I am on a Peak rate. However, the peak rate is not a time-of-day rate. The peak rate is a useage peak rate where I am charges $10 per KW used in my highest 15 minute "peak" in a single billing cycle. In addition, I still have to pay for total KW in a billing cycle. Therefore, If I am charged $120 for my total KW in a single billing cycle, but my highest 15-minute peak is 15KW, my total bill would be (15KW x $10) = $150; plus the $120 total KW charge for a total bill of $270. Reduce the peak useage and I can greatly reduce my bill.

Clear as mud?

Anyway...

If I can cut my useage in half at night when charging my Nissan Leaf, I can cut my bill by about $80/month by reducing my peak useage during charging. My question is is it safe for a battery to have a frequent on/off cycle of 5-7 minute intervals? If so, I can charge a cycle timer. If not, I need to search for a lower amp L2 Charger.

I would prefer the cycle timer so I could override the charge in an emergency and during winter when peak use is not as much of an issue. Nov - Feb will always be high useage for me.

I drive a 2014 Leaf SV

it is perfectly safe to use a cycle timer or rather let me clarify.

Its "just as safe" as driving the car. If you have noticed, you constantly go from discharging to charging depending on driving conditions and at MUCH greater power than any home L2 will do so cycling every 5 mins or whatever is fine. You can also get a modified EVSE (or get your modified) that will allow an adjustable rate of charge. It is rare that one needs the full 6.6 KW rate for an overnight charge any way but the money spent (even $300 to modify) would be tough to justify.

I personally think you could easily charge at night without any increase to your bill at all. What is your current peak charge average per month now? you mention 15 KW which is a "bit" high. I would venture to think that you have something huge going on or that your usage overnight would normally drop significantly enough that your car could charge under your daytime peak.

The batteries might see these charge cycles as regen and not care, but the charger or evse will.

When the timer cycles on, the evse powers up, communicates with the leaf, negotiates a charging speed, and then flips the relays and starts charging. This whole process takes about 5-10 seconds (depends on how long the evse takes to power up). Normally this only happens once a night without the cycle timer. But with the timer in place, it'll be going through this process every 15 minutes (5 mins on, followed by 10 mins off?) for ~9-12 hours (to get 3-4 hrs of effective charge time ... 36-48 cycles). That would be the equivalent of charging the car every day for 100 years in just 3 years time. That's bound to take a toll on either the evse or the car's charger.

 

[DaveinOlyWA]

I have looked everywhere (including this site) and do not see an answer to this problem.

I live in Juneau, AK. I am on a Peak rate. However, the peak rate is not a time-of-day rate. The peak rate is a useage peak rate where I am charges $10 per KW used in my highest 15 minute "peak" in a single billing cycle. In addition, I still have to pay for total KW in a billing cycle. Therefore, If I am charged $120 for my total KW in a single billing cycle, but my highest 15-minute peak is 15KW, my total bill would be (15KW x $10) = $150; plus the $120 total KW charge for a total bill of $270. Reduce the peak useage and I can greatly reduce my bill.

Clear as mud?

Anyway...

If I can cut my useage in half at night when charging my Nissan Leaf, I can cut my bill by about $80/month by reducing my peak useage during charging. My question is is it safe for a battery to have a frequent on/off cycle of 5-7 minute intervals? If so, I can charge a cycle timer. If not, I need to search for a lower amp L2 Charger.

I would prefer the cycle timer so I could override the charge in an emergency and during winter when peak use is not as much of an issue. Nov - Feb will always be high useage for me.

I drive a 2014 Leaf SV

it is perfectly safe to use a cycle timer or rather let me clarify.

Its "just as safe" as driving the car. If you have noticed, you constantly go from discharging to charging depending on driving conditions and at MUCH greater power than any home L2 will do so cycling every 5 mins or whatever is fine. You can also get a modified EVSE (or get your modified) that will allow an adjustable rate of charge. It is rare that one needs the full 6.6 KW rate for an overnight charge any way but the money spent (even $300 to modify) would be tough to justify.

I personally think you could easily charge at night without any increase to your bill at all. What is your current peak charge average per month now? you mention 15 KW which is a "bit" high. I would venture to think that you have something huge going on or that your usage overnight would normally drop significantly enough that your car could charge under your daytime peak.

The batteries might see these charge cycles as regen and not care, but the charger or evse will.

When the timer cycles on, the evse powers up, communicates with the leaf, negotiates a charging speed, and then flips the relays and starts charging. This whole process takes about 5-10 seconds (depends on how long the evse takes to power up). Normally this only happens once a night without the cycle timer. But with the timer in place, it'll be going through this process every 15 minutes (5 mins on, followed by 10 mins off?) for ~9-12 hours (to get 3-4 hrs of effective charge time ... 36-48 cycles). That would be the equivalent of charging the car every day for 100 years in just 3 years time. That's bound to take a toll on either the evse or the car's charger.

Ok, I chose to answer the OP instead of interpreting what he wanted to hear and it would appear it is not.

now, not sure what the cycle counts any of these items are rated for but pretty confident that the lowest one will be the socket itself. but in this scenario, its plugged into once a night. Now, I have heard of socket failures (some rather spectacular) and random EVSE weirdness so in reality, anything could happen but I have also seen several LEAFs with 4,000+ charging "events" so I have to say, he got time...

What has not been addressed is whether this will be an effective way to avoid the demand charges. Its my opinion it is not. The other thing is how many partial plug in hours will be needed to gain a full charge. again, I think he will discover other more pressing issues.

 

[AntronX]

OP, what is the brand and model of the charger you have installed? It may have pilot signal adjustment inside to set max charging current.

 

[Oils4AsphaultOnly]

Ok, I chose to answer the OP instead of interpreting what he wanted to hear and it would appear it is not.

now, not sure what the cycle counts any of these items are rated for but pretty confident that the lowest one will be the socket itself. but in this scenario, its plugged into once a night. Now, I have heard of socket failures (some rather spectacular) and random EVSE weirdness so in reality, anything could happen but I have also seen several LEAFs with 4,000+ charging "events" so I have to say, he got time...

What has not been addressed is whether this will be an effective way to avoid the demand charges. Its my opinion it is not. The other thing is how many partial plug in hours will be needed to gain a full charge. again, I think he will discover other more pressing issues.

Acknowledged. Although you've seen evidence of it being fine for the car, I think I've shown that the numbers from a cycle timer will far exceed that evidence (120 summer days * 40 cycles per day + 245 winter days of 1 cycle = 5,000+ charging events within a year), and thus "perfectly safe" for the long term is in doubt.

 

[sub3marathonman]

What has not been addressed is whether this will be an effective way to avoid the demand charges. Its my opinion it is not.

I mentioned that previously.

It is also a bit onerous as the demand is a rolling calculation, incrementing every 5 minutes, instead of starting over every 15 minutes or 30 minutes. So he can't even leave the charger on for 10 minutes, from 1:10 a.m. to 1:20 a.m., which if it was set time-slots for the demand calculations could be done. Theoretically, even two seconds of usage could overlap into two of the three intervals.

 

[DaveinOlyWA]

Ok, I chose to answer the OP instead of interpreting what he wanted to hear and it would appear it is not.

now, not sure what the cycle counts any of these items are rated for but pretty confident that the lowest one will be the socket itself. but in this scenario, its plugged into once a night. Now, I have heard of socket failures (some rather spectacular) and random EVSE weirdness so in reality, anything could happen but I have also seen several LEAFs with 4,000+ charging "events" so I have to say, he got time...

What has not been addressed is whether this will be an effective way to avoid the demand charges. Its my opinion it is not. The other thing is how many partial plug in hours will be needed to gain a full charge. again, I think he will discover other more pressing issues.

Acknowledged. Although you've seen evidence of it being fine for the car, I think I've shown that the numbers from a cycle timer will far exceed that evidence (120 summer days * 40 cycles per day + 245 winter days of 1 cycle = 5,000+ charging events within a year), and thus "perfectly safe" for the long term is in doubt.

"40 cycles per day?"

well it would appear that part of the confusion is we are reading different books here :shock:

 

[wwhitney]

"40 cycles per day?"

The OP said that the peak demand is calculated over a 15 minute time period. So that would be one cycle per 15 minutes, or 4 cycles per hour. If charging for 10 hours (at the reduced charge rate from all this cycling), that's 40 cycles.

Cheers, Wayne

 

[BillHolz]

The best option is to use an EVSE that allows the correct KW draw. The cheapest option to do that is to convert the EVSE that came with the vehicle as per this thread: http://www.mynissanleaf.com/viewtopic.php?f=26&t=16948 (My post on pg 9)

I did this and it works well both at home and while travelling. Using this upgrade at under $100 should keep the wife happy enough. It will draw 240Vx12A= 2.88KW which is just slightly more than his lowest demand throughout the year. If not increasing the demand at all is the requirement, use the modified EVSE at 120V using an adapter during the lowest demand months of the year, the modified EVSE at 240V the rest of the year.

The only time the full amp draw EVSE can be used is during peak usage months at off peak usage times of the day so perhaps sell it on ebay.

 

[bowthom]

Hello,
Build a little cycle timer that opens and closes the "prox" signal. Pretty simple to do.

 

[jpadc]

Hello,
Build a little cycle timer that opens and closes the "prox" signal. Pretty simple to do.

Very few EVSEs come wired to receive the proximity signal all the way up from the car to the control box (but a few do). However, nothing to stop the end user from adding a wire from the proximity switch out of the J1172 handle to a small box attached to the cable itself. Just need a timer and likely a battery to power it with a simple low voltage relay to cut and restore the proximity signal and it would work (and very safely to). Just has to simulate someone pressing the release button on the handle and the car will drop the amperage draw.

I like this idea. Way more comfortable than the cot out by the car.... Not sure doing any of this is a good idea and I have no idea if it will actually reduce the electric costs for OP, but it would do what was requested.

 

[AntronX]

Another idea is to add a micro controller circuit to intercept and modify PWM duty cycle of pilot signal to fool the car into pulling less current.

 

[jpadc]

Another idea is to add a micro controller circuit to intercept and modify PWM duty cycle of pilot signal to fool the car into pulling less current.

To the best of my knowledge, there is nothing in the protocol that requires the vehicle to continuously monitor the PMW duty cycle, only to register it when first connected. Now the LEAF might and might respond by reducing the draw.

However, the EVSE is required to continuously monitor it in case the car turns it negative and respond by disconnecting power and generating an error state (in case of a short or the like), but I don't know if the signal were to be returned to a positive state if the EVSE would clear the error state and continue charging.

So this one MIGHT work, but your other suggestion (cutting the proximity signal) is far more elegant.

 

[bowthom]

Another idea is to add a micro controller circuit to intercept and modify PWM duty cycle of pilot signal to fool the car into pulling less current.

To the best of my knowledge, there is nothing in the protocol that requires the vehicle to continuously monitor the PMW duty cycle, only to register it when first connected. Now the LEAF might and might respond by reducing the draw.

However, the EVSE is required to continuously monitor it in case the car turns it negative and respond by disconnecting power and generating an error state (in case of a short or the like), but I don't know if the signal were to be returned to a positive state if the EVSE would clear the error state and continue charging.

So this one MIGHT work, but your other suggestion (cutting the proximity signal) is far more elegant.

The car will respond to the PWM signal. I have tested this in real time and it was almost perfect in its tracking.

 

[gshepherd]

Seems like using a network connected EVSE that can adjust the pilot signal in real time would be a neat solution, if the OP is up for some scripting / programming or knows someone who could help. I know my OpenEVSE with Wifi board allows adjustments to the pilot signal in real time via very simple commands send over a network connection.

We were playing with that using a dedicated Raspberry pi to detect start of charge taper and cut off charging altogether to save some room in the pack for regen down the mountain we live on. The program even displayed a custom message on the OpenEVSE LCD and monitored for another event to allow 100% charge.

I seem to recall the pilot signal can advertise as low as 6A to the car. Some folks here with PV solar installations use this to have the car track array output in real time and minimize consumption from the grid.

 

[arnis]

5 minute cycles will add additional wear to contactor relay. I do not recommend that.
Also if you de-energize EVSE with some device it also wears down the added relay.
Adjustable EVSE is the best option. If you are in US I do not recommend 120V as it
loses in charging efficiency. But you could use modified portable EVSE that came with
the car. It can be modified to 230V input and it will still draw 12A (or whatever current
it draws on 110V). EU brick doesn't need to be modified. 10A draw fixed.

 

[jpadc]

5 minute cycles will add additional wear to contactor relay. I do not recommend that.
Also if you de-energize EVSE with some device it also wears down the added relay.

That is the beauty of AntronX's suggestions. Either one produces no wear on the contactor nor de-energizes the EVSE. And IF the LEAF will continuous monitor the pilot signal (and adjust draw accordingly, then what OP wants could likely could be programmed into an OpenEVSE. The OpenEVSE board only (using the parts from the OP's current EVSE) is not that expensive.

Others have asked if doing so would actually save money and, if I understood it all, I think its very questionable (but so is my understanding of that rate plan) Thank goodness I don't live some place that has such crazy rate plans.

 

[ermackey]

OP, what is the brand and model of the charger you have installed? It may have pilot signal adjustment inside to set max charging current.

Sorry. Been Away and did not realize new posts were being made.

I have two chargers. A 3.3KW Cipper Creek and a 7 KW GE (the one in the ugly white box). I have the GE one dropped to 2.7 kw using the jumper, but could get it back to 3.3, 5 kw, or 7KW, should I desire.

I might have stumbled on a solution myself.

My home does not exceed 2KW draw any time except when the dryer, car charger(s), or water heater is on. During peak useage (February), my average daily use rate is below 4.2kw/hr.

New solution idea:
Using a Samsung Smartthings Hub and a few Z-wave relays, I can put my Hot Water and two car chargers, on Z-wave "smart" switches. One of the new app features is the "Max Energy" app that turns off specific devices as KW consumption is reached. I could "tier" my appliances to operate on a priority tier ranking. AEON makes a energy monitor that works with Smartthings to utilize this feature.

For example:
1. Dryer - No switch and uses a peak useage of 4.5 KW
2. Hot Water Heater Turn Off when KW > 6 kw
3. Car Charger #1 - Turn off when KW > 5.5 kw (In-car program charge 8am - 8pm)
4. Car Charger #2 - Turn off when KW > 5.5 kw (In-car program charge 8pm - 8am)

In conjunction with this, I can keep the cars on a timer to prioritize loads and minimize "switching" frequency. This is the way I picture the functioning.

I have a heat pump, but my total load never exceeds 2 KW load unless a car charger, dryer, or water heater turns on. My Water heater is a 4.5KW load (Rheem Marathon). My electric dryer is also a 4.5KW dryer. I could care less about my water heater switching off and on, gven the choice of the water heater or a car charger.

1. Anytime the dryer is on, everything but the hot water heater is "off". The hot water heater will not come on until the dryer reaches temp and KW draw decreases. Most times, the dryer will not be used, but this arrangement allows it to be without blowing a hole in my peak rate.
2. Hot Water heater is #2 priority and will switch-on anytime that the Dryer is not on or is maintaining heat (dryer wattage drops to about 1.5kw after reaching temp) throughout the day. Dryer priority is important for new baby and so is hot water. This will also keep either car from charging as either load will cause the smartthings to keep the circuit "off" to car chargers.
3. During day (8am 8pm) usage of the dryer and/or hot water heater would turn off charger #1. Charger #2 is programmed off during that time and never competes with Charger #1.
4. During the evening (8pm - 8am), Charger #2 is programmed to charge unless the water heater turns on. Dryer is not an issue at this time and Charger #1 is programmed off at that time.

What do you think? Clear as mud?

 

[sub3marathonman]

I might have stumbled on a solution myself.

...

1. Anytime the dryer is on, everything but the hot water heater is "off". The hot water heater will not come on until the dryer reaches temp and KW draw decreases. Most times, the dryer will not be used, but this arrangement allows it to be without blowing a hole in my peak rate.

...

What do you think? Clear as mud?

I have similar dilemmas, as I am on a demand rate too, because I have PV solar.

I monitor every circuit through a Brultech GEM (not associated with them: http://www.brultech.com/)

Now, what is "interesting" or should I say aggravating is that dryers are set up to destroy demand rate customers. When you're running the dryer, the heating element will come on for a few minutes, and stay off for a few minutes, come on for a few minutes, etc. Now, demand is the maximum for the 5-minute time interval, so instead of heating for 15 minutes, the dryer heats for 15 minutes over 30 minutes, thus doubling its demand.

So if you're keying other items to be "off" during the time the dryer is running, it could be an on again, off again, on again, off again situation, which wouldn't be good.

I don't know if it is possible, but I would try to set up a time-slot for when the dryer can be run, and have everything else off completely during that time-slot.

 

[GerryAZ]

I have a hard-wired load (demand) controller that is programmed to shed loads from lowest priority to highest priority. The relay for the dryer only opens one line so it opens the heating element and allows the motor to continue tumbling the clothes. The hot water tank is lowest priority and the two heat pump compressors have the same priority so they alternate. The air handlers are not shed so air circulation continues. The dryer is the highest priority. The unit I have is capable of controlling 8 loads with addition of relays so I could use an additional relay to switch the utility load shed input in my EVSE if I needed it. I have the advantage that 9:00 pm to 9:00 am M-F and all day Sa and Su are off peak with unlimited demand so I just programmed the Leaf to charge only off peak.

Normal utility demand rates are based upon 15-, 30-, or 60-minute demand intervals. I suggest you look at your bill to see what time base your demand charge has. If it is based upon 15 minutes, you can run a 3 kW load for 7-1/2 minutes and have a demand charge for 1.5 kW. If it is a 30-minute demand rate, you can run that same 3 kW load for 15 minutes and have a 1.5 kW demand charge. If it is a 60-minute demand rate (what I have), you can run 3 kW for 30 minutes, 6 kW for 15 minutes, or 1.5 kW continuous and still have a demand of 1.5 kW.

Your plan to use smart devices should allow you to accomplish your goal.