Wanted: Automatic Switching for EVSE power from two Sources

[TonyWilliams]

I would like to be able to have a timer that would allow my EVSE to be powered by electrical source A during the time from 12:10am until 4:50am, and then from electric source B the rest of the time.

Both electric busses are already wired near my unit, but now I must manually unplug from one bus to the other.

Ideas.

 

[palmermd]

How about a reversing motor starter with the coil fired from a simple time clock. A single outlet could switch sources.

 

[davewill]

I assumed that part of the deal for getting SDG&Es lower EV Study TOU rates was that I was supposed to refrain from plugging the car into the house meter to avoid the peak rates. If this kind of thing becomes widespread, we can probably kiss any special EV rates in the future goodbye.

 

[TonyWilliams]

I assumed that part of the deal for getting SDG&Es lower EV Study TOU rates was that I was supposed to refrain from plugging the car into the house meter to avoid the peak rates. If this kind of thing becomes widespread, we can probably kiss any special EV rates in the future goodbye.

You can kiss it goodbye anyway. Since they already know that virtually everybody charges at night, regardless of the rate, I expect my 7.7 cents to go away.

Otherwise, I'll just run everything off the solar, and use no switch.

 

[essaunders]

How about a 240V automatic transfer switch and some other controlled relay on one of the sources.


Or just build something --- Can't be that hard - all the components are already part of EVSE design....

 

[davewill]

I assumed that part of the deal for getting SDG&Es lower EV Study TOU rates was that I was supposed to refrain from plugging the car into the house meter to avoid the peak rates. If this kind of thing becomes widespread, we can probably kiss any special EV rates in the future goodbye.

You can kiss it goodbye anyway. Since they already know that virtually everybody charges at night, regardless of the rate, I expect my 7.7 cents to go away.

Otherwise, I'll just run everything off the solar, and use no switch.

Rationalize it any way you have to.

 

[garsh]

Well, I found some switches that can handle two AC sources:
120vac source switch.

But I couldn't find anything that was programmable, or on a timer.

 

[smkettner]

Use two timers on one circuit. Just set so they come on or go off when needed.

Sorry misread. Use a timer on one source and an automatic transfer switch on the other. Timer comes on and the switch will flip over. Timer goes off, switch goes back.

google 240v timer

google 50 automatic transfer switch

Transfer switch will need a neutral as the control runs on 120v.

 

[DaveEV]

This could be done with a couple of 40A 240V DPDT relays and a basic 120V timer.

Basically, the 120V timer would be wired to turn on one relay when on and the turn off the other relay when off. Just need to find the right relay (I'm sure someone here will dig one up!)

Ideally you'd set up a small delay between flipping the relays so you don't end up with both powered at the same time, but as long as you make sure that you've got each leg wired the same way you shouldn't have any issues.

Have them wired out-of-phase and you'll likely trigger a brief short-circuit when the relays flip!

 

[camasleaf]

Have them wired out-of-phase and you'll likely trigger a brief short-circuit when the relays flip!

http://www.plccenter.com/Shop/MAGNECRAFT/W199AX14" onclick="window.open(this.href);return false;

A DPDT should be able to do the job by it self. Put the EVSE on the terminals connected to the moving part and the two sources at the fixed contacts.

For 240V sources (with 40A breaker in the panel) I would be more confortable with two contactors with interlocks so only one can be ON at any time. The closing circuit on one source uses a normaly closed contact on the other source and viceversa. This way even if the timer messes up the source to close will have to wait for the other to open.

There should be automatic transfer switches out there that the timer can trigger the switch. That will be the best option.

 

[smkettner]

A transfer switch cannot connect both as to connect one it must release the other. That is just the mechanics of the double throw switch.

You could easily put a timer direct in the control circuit so the timer would not be switching the main power. These switches are very low tech.

 

[BRBarian]

A transfer switch cannot connect both as to connect one it must release the other. That is just the mechanics of the double throw switch.

You could easily put a timer direct in the control circuit so the timer would not be switching the main power. These switches are very low tech.

Yes. That's what you want. You could go with the Generac RTSX100A3 for about $350. It would be easy to get that to work, and they're widely available (e.g. Home Depot).

 

[ElectricVehicle]

This looks like it's suitable for your needs:

GE 24-Hour Outdoor Mechanical Box Timer, On/Off, DPDT
Model # 15135
Internet # 202788238
Store SKU # 136628
$54.00 /EA-Each
http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10053&langId=-1&locStoreNum=6175&productId=202788238&storeId=10051" onclick="window.open(this.href);return false;

Yup, if it's what's in this QuickStart, it should do the trick. The DPDT contacts are completely independent of the time mechanism, so you can wire them up however you choose.
http://www.jascoproducts.com/timer/QuickStartGuide.pdf" onclick="window.open(this.href);return false;

I couldn't find the manual for the 15135. Maybe they are doing monkey business like different model numbers for different business channels or retail outlets, just to be difficult!

Also a digital version:
http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?productId=202788241&storeId=10051&langId=-1&catalogId=10053" onclick="window.open(this.href);return false;

Found this by Googling for
mechanical timer DPDT
You can see more options Googling for "timer DPDT", but that includes lots of low current results, so there's more results to sift through.


Some GE Timer manuals:
http://www.jascoproducts.com/support/timer-quick-start-guide.asp" onclick="window.open(this.href);return false;

 

[TonyWilliams]

This is confusing on the specs:

Amperage (amps) : 40 A
Voltage (volts) : 277 V
Wattage (watts) : 0 W

Ideal for use with indistrial applications such as fans, pool heaters, pumps, air conditioning, heaters, blowers and lighting. It offers selectable voltage and a NEMA 3R rated enclosure. The box is heavy-duty, rain tight rust proof metal construction.

 

[Randy]

Hi Tony,
Just to clarify, and some or most of this info was mentioned at the Poway LEAF meeting before last...The current experimental EPEV-Y and EPEV-Z rates are priced lower than what it costs to provide that service and energy for the super off-peak period. It is part of the rate study to see how those low rates influence charging behavior.

In addition, when the rate study concludes (roughly when the EV Project also concludes, not sure of exact dates yet), the experimental EV rates will be closed and all participants will be asked to choose an existing rate to transition to (DR, EV TOU, EV TOU2, etc.). I am not aware of any new rates coming down the pipe, but anything can happen between now and then...Most likely we will all have to choose a rate that is already on the books. We are talking internally about communicating this information officially to all the study participants, but will probably wait just a bit longer to get more definitive date information...So be on the lookout for that....

As far as your power switching project, here's a couple of concerns/thoughts from me...

I would be concerned doing full-current 240v switching on the EVSE input power on a frequent basis. Unless you have some fancier solid-state switching that can help reduce surges, I wouldn't want to do that regularly. And once you switch power sources, would the EVSE reboot and pick right up where it left off and start to charge again on the new source? I'm not sure about that...Screen calibration, etc...

A thought about cost...If you're talking about a timer and the midnight to 5am time period, even a fully dead LEAF will charge up in a short time over 5 hours (what is it, maybe 6 hours?). So you're thinking of implementing this timer setup to avoid the cost difference between your lower DR tier and the off-peak price of 17 cents (if you're on EPEV-Y) for about an hour or so? Maybe 9 or 10 cents per kWH difference? So for an hour, consuming nearly 4 kWH, that difference in switching from one circuit to another would be about 40 cents per incident (and only when the car is nearly empty)?

That seems like a lot of trouble to avoid a little bit of extra cost...But, then again, I've been known to do stuff just to figure it out...

 

[TonyWilliams]

I use my EVSE a lot in thel peak time of noon to 8pm. So, currently, I have to drag out the Panasonic EVSE from the hatchback, and plug it in my NEMA 6-50 receptacle, hooked up to the solar, or pay the substantial increase of the TOU-EV rates for that period.

It's likely that when the rate changes from my $.077 rate from midnight to 5am that I will just bypass the dedicated EV meter altogether, and go with a straight solar / grid connected system. Then, I could charge whenever I wanted, with little concern for the cost (or the grid).

For now, I just want to play with the possibilities. Your concerns about a simple timer are valid, and I'd be more inclined to get a solid state transfer switch. Unfortunately, I don't see one yet that would work.

 

[Randy]

Ok, I understand that...

So, here's another idea....

What if the EVSE were re-wired so that it always received power to operate the electronics from one source, and the contactor was rewired so that the high-current source for charging was wired into the relay or switch to go between sources?

If isolation could be achieved between the sources and the unit would operate correctly, then only the contactor power would be switched and the EVSE wouldn't have to reboot to keep going through a switch cycle...

A little bit custom, but that could be a little bit easier on the EVSE...

 

[TonyWilliams]

Ok, I understand that...

So, here's another idea....

What if the EVSE were re-wired so that it always received power to operate the electronics from one source, and the contactor was rewired so that the high-current source for charging was wired into the relay or switch to go between sources?

If isolation could be achieved between the sources and the unit would operate correctly, then only the contactor power would be switched and the EVSE wouldn't have to reboot to keep going through a switch cycle...

A little bit custom, but that could be a little bit easier on the EVSE...

Yes, that's actually an excellent idea. Easy to do, too. And cheap, with a $60 timer.

So, to think of the wiring. If two timers were used, with slight overlaps between the two (Ok, it sounds hokey, but I'm sleepy).

 

[ElectricVehicle]

This is confusing on the specs:

Amperage (amps) : 40 A
Voltage (volts) : 277 V
Wattage (watts) : 0 W

Ideal for use with indistrial applications such as fans, pool heaters, pumps, air conditioning, heaters, blowers and lighting. It offers selectable voltage and a NEMA 3R rated enclosure. The box is heavy-duty, rain tight rust proof metal construction.

These types of units are commonly used to switch pool pumps, which is a much nastier load to switch than many EV Chargers. They can be configured to operate from 120V, 208V, 240V and 277V. It's 0 W, I guess because they didn't fill out all the specifications. The timer mechanism would consume a couple watts. The relay ratings are up to 277V and up to 40A, the EVSE, especially for the 'Eric the half a bee" 3.3 kW charger at 240V, 16A is well within these parameters. The device should last a long time being rated for 40A but only switching 16A, in the worst case - if it switches while charging. Most times it will be switching less than an amp - as the EVSE won't often be charging during the switch period, depending on your actual usage patterns.

 

[DaveEV]

These types of units are commonly used to switch pool pumps, which is a much nastier load to switch than many EV Chargers.

Do you think the referenced DPDT timer will work? The quick start guide seemed to indicate that the COM terminals should always be powered in parallel with the timer power and the load hooked up to the NC or NO terminals. For Tony's use the EVSE would have to be wired into the COM terminals and the two power sources plugged into the NC / NO terminals (with one of those wired into the timer).