Delayed Charging to Leverage Time of Use Utility Rates

[coupedncal]

I am looking to purchase an EVSE and the obvious choice is

(1) To get a make that supports delayed / specific time for start of charging. Eg.
http://www.emotorwerks.com/products/online-store/product/show/202-juicebox-pro-40
http://www.amazon.com/dp/B00MFVI92S/ref=wl_it_dp_o_pC_S_ttl?_encoding=UTF8&colid=37BC6TLSTF9OG&coliid=I2WH0WFSFXQBJ0

OR
(2) Get a simple EVSE unit that just turns on and turns off and I control the charging via in car configuration.
http://www.emotorwerks.com/products/online-store/product/show/198-juicebox-classic-30

My obvious preference would be to get (2) as that will save me $100.

Now here is my use case.

I plan to charge at home using the delayed charging option and turn on L2 charger at midnight.
I plan to charge at work 50% of the time and of course i'd like to not use delayed charging there. We get first come first serve charging at work so my charging time cannot be predicted in advance.

My question is could we configure the car to perform delayed charging at home but create an override feature for the work charging and charge immediately upon connecting the EVSE at work? Apparently, Nissan Leaf offers an override option that starts charging immediately if you hit the override button but i have not found this option on our i3.

 

[barrychan]

I am still trying to figure out this brand new vechle, i think you can set the start to finish time but if you want to change the setting, each time you shut off the car the setting will come up and you can leave it or change it to immediately, change to low, reduce or max.....up to you

 

[jadnashuanh]

It's a checkbox on the menu...use low-rate charging time window or not.

One thing to consider, if you select a departure time, and that is outside of the low-rate time window, the car WILL turn on the EVSE to keep the battery up while it is warming things up. This can take up to 3.5-hours, depending on the temperature of the battery pack at the time (note, actually charging the battery will warm it some, so it may not have as far to go verses say not using a time window...it could have had all night to cool off, so that may be advantageous as an energy saving technique to merge those two windows as close as possible). My estimate is that the vehicle could use as much as 2Kw on a really cold night to condition the batteries as triggered by using the departure time (conditioning the cabin is optional, but adds maybe a bit more).

There's maybe a third option...some home automation systems can control power loads like an EVSE. Just make sure you get an EVSE that will reconnect after a power outage that that type of control would look like to it. Some will detect a fault if connected to the car and the power cycles on the input to the EVSE and then never allow charging to occur...it must have power before you plug the vehicle in. I know the Clipper Creek units specifically guarantee this capability.

 

[coupedncal]

Thanks for this detailed analysis. Considering the low rate charging time is in the midnight to 6am window, it makes sense to keep the departure times before the end of the low-rate window even on days when one is not planning on driving the car. This will waste some Kw but at least this wastage will from the low cost grid juice and not from the valuable battery juice.

 

[jadnashuanh]

Note, the car will not utilize the departure time and warm the batteries unless it is plugged into an EVSE. OTOH, you can precondition the cabin any time you want, whether on the EVSE or not. If it is on the EVSE, once the battery level drops enough (1-2%? or so), it will turn back on to top off the batteries if it wasn't already on. If you have the heat pump, warming the cabin isn't as big of an energy hit as if you have the REx or don't have that option (it's standard in the USA), as then, resistance heating is 1:1...heat pump is 3-4x more efficient.

 

[Anonymous]

Cheapest alternative here in Ontario where peak rate stops at 8PM and drops down to low rate:

1. Use L1 OEM EVSE that came with the car.
2. Plug in when you get home at 6PM.
3. The L1 takes 8-12 hours to charge the car.
4. The majority of the time charging is during off peak.
5. For the 2 hours plugged in pay 5c more per kWh, or 10c per day.
6. Add 10c per day and you will NEVER get payback on purchase of L2 EVSE.

Just a thought.

 

[jadnashuanh]

Most people don't nearly discharge their whole battery, but if you do, it's closer to 19-hours to recharge an i3 with the level 1 EVSE that comes with the car! Kind of useless if you want to go out in the evening for something and burn up some more watts. It depends a lot on what the time window of your low-cost charging is and how far you drive with the resulting SOC that needs to be replenished. SOme places have a huge difference between 'normal' and low-cost charging prices. That makes a difference, too.

 

[barrychan]

I think the rule of thumb for our BEV is if you use about 50 % a day and no out of town long distance travel....its perfect and you should have a full charge everyday and charged at the lowest electricity rate with L1

If you use most of the battery daily, then you will need a L2 charger.

We are lucky, our electricity peak is only 14 cents a kw, 7pm to 7am is only 8 cents a kw, weekend and holiday is 8 cents all day

 

[coupedncal]

I think the rule of thumb for our BEV is if you use about 50 % a day and no out of town long distance travel....its perfect and you should have a full charge everyday and charged at the lowest electricity rate with L1

If you use most of the battery daily, then you will need a L2 charger.

We are lucky, our electricity peak is only 14 cents a kw, 7pm to 7am is only 8 cents a kw, weekend and holiday is 8 cents all day

I am in the Bay Area, CA and our rates go from 9.5cents during off peak hours to 44cents during peak summer hours. At the peak rate, it becomes as expensive to charge as driving an ICE. :twisted:

Does anyone here has real life experience using the method that was earlier recommended ? Ie set the recurring time to charge at midnight at home and when it comes to charging at work then at the time of engine shutdown, choose charge immediately for the next time. Does that retain the recurring cycle or does it wipe it off with immediate and one has to reprogram the nightly charge job?

 

[coupedncal]

Just a quick update. I just enabled low cost charging for 10:10pm and I plugged in my level 1 charger at 10:05pm thinking the charging won't start until 10:10pm but guess what. The charging started as soon as I plugged the cable in. I double checked and it was not on charging immediately but on low cost charging. Now i am stumped why this didn't work. Any ideas? Does low cost charging not work with level 1 charging?

 

[PhilH]

It depends on your departure time. If the i3 thinks it needs to start charging immediately in order to be fully charged by the departure time, it will do so.

 

[psquare]

Our UK area off-peak rate window is 1:30am - 8:30am. I set departure time on weekdays to 8:15am and a low rate charging window of 2am to 8:15am.

This morning I noticed that at 8am the car was back on 97% (despite having been on 100% earlier on). I've seen a similar behaviour when preconditioning in March. I guess the important thing is to find the 'sweet spot' of when to start charging the car during the off-peak period in order to minimise the cooling down effect before the 3h precon starts.

BMW and the iRemote software should be a little smarter here. Why not separating the departure time and off-peak charging in the app and allowing 2 different time ranges? I guess it might be difficult for some customers to get their head around this.

 

[coupedncal]

It depends on your departure time. If the i3 thinks it needs to start charging immediately in order to be fully charged by the departure time, it will do so.

That now totally makes sense. You guys know your cars well.

 

[barrychan]

We have a smart car

 

[PhilH]

Note that another occasion when off-peak charging does not work is when you plug the car in when it has a low SoC (probably less than something like 15-20%). In this case it will start charging immediately. To take advantage of off-peak, let it charge a bit, then unplug it and plug it back in.

My presumption is that it does this to protect the condition of the battereies.

 

[jadnashuanh]

WHen you park with low batteries, especially in the winter, the drop in temperature overnight will decrease the capacity even further. They'll last longer when they have some minimum charge.

It's unfortunate that BMW doesn't explain much of this in the manual, but then, few people read the thing anyways, and it's already quite long.

 

[WoodlandHills]

Note that another occasion when off-peak charging does not work is when you plug the car in when it has a low SoC (probably less than something like 15-20%). In this case it will start charging immediately. To take advantage of off-peak, let it charge a bit, then unplug it and plug it back in.

My presumption is that it does this to protect the condition of the battereies.

Good point, this happened last week, it ignored my settings and began to charge immediately. I had to unplug and wait until it was my low cost period to plug back into the EVSE, but by the time I had caught it the SOC was up to 90%. Too bad it isn't smart enough to stop once it reaches whatever SOC triggers the override of my settings.

 

[WoodlandHills]

WHen you park with low batteries, especially in the winter, the drop in temperature overnight will decrease the capacity even further. They'll last longer when they have some minimum charge.

It's unfortunate that BMW doesn't explain much of this in the manual, but then, few people read the thing anyways, and it's already quite long.

I think more people would read the manual if it was more useful. Some of the length is due to systems for other markets being included in our NA book. Is it really so hard or so expensive to simply delete extraneous content before printing? Surely the profit structure of the i3 Program can afford better documentation before BMW begins to lose money!

 

[rabster]

WHen you park with low batteries, especially in the winter, the drop in temperature overnight will decrease the capacity even further. They'll last longer when they have some minimum charge.

It's unfortunate that BMW doesn't explain much of this in the manual, but then, few people read the thing anyways, and it's already quite long.

I think more people would read the manual if it was more useful. Some of the length is due to systems for other markets being included in our NA book. Is it really so hard or so expensive to simply delete extraneous content before printing? Surely the profit structure of the i3 Program can afford better documentation before BMW begins to lose money!

I agree. the user manual is completely pointless as it only explains the stuff that's blatantly obvious but then completely ignores the useful info which would not be so obvious.

WRT the charging, thanks for the replies on this as I also noticed this week that the charging was starting immediately regardless of my off-peak settings. Now it has been explained, it makes sense!