Wanted: Automatic Switching for EVSE power from two Sources

[ElectricVehicle]

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).

The quick start guide said explicitly that there is no internal connection from the timer power supply to the DPDT relay. To use it as an ordinary timer, you have to make that connection externally with a wire jumper on the terminal block. That means if you don't add the jumper, the relay contacts come out to the terminal block with no internal connections. This is EXACTLY what we want for this application - EVSE on COM, electrical source 1 on "NC" (Normally Closed), and electrical source 2 on "NO" (Normally Open).

 

[DaveEV]

The quick start guide said explicitly that there is no internal connection from the timer power supply to the DPDT relay. To use it as an ordinary timer, you have to make that connection externally with a wire jumper on the terminal block. That means if you don't add the jumper, the relay contacts come out to the terminal block with no internal connections. This is EXACTLY what we want for this application - EVSE on COM, electrical source 1 on "NC" (Normally Closed), and electrical source 2 on "NO" (Normally Open).

Got it - so it will do exactly what Tony wants for ~$60 in a prebuilt self-contained box.

 

[kubel]

Rationalize it any way you have to.

My utility has a similar 'experimental electric vehicle' program and there is absolutely nothing in the terms of service that I could find that says I can't charge on normal residential rates if I wanted to. It just says that only J1772 compliant, highway capable, registered vehicles can make use of the dedicated meter. Though it might provide utilities with skewed figures.

Time of Day:
14 cents per kWh on peak.
3.5 cents per hWh off peak.
$1.95/mo service charge.
4.195 cent per kWh delivery charge (off/on peak).

--or--

Flat Fee:
$40/mo

For the amount of driving I do, the $40/mo rate is tempting. But I'll probably be charging all day at work, and at night at home, so time-of-day is probably a much better deal for me.

 

[TonyWilliams]

The quick start guide said explicitly that there is no internal connection from the timer power supply to the DPDT relay. To use it as an ordinary timer, you have to make that connection externally with a wire jumper on the terminal block. That means if you don't add the jumper, the relay contacts come out to the terminal block with no internal connections. This is EXACTLY what we want for this application - EVSE on COM, electrical source 1 on "NC" (Normally Closed), and electrical source 2 on "NO" (Normally Open).

Got it - so it will do exactly what Tony wants for ~$60 in a prebuilt self-contained box.

Will one of you smart guys draw this on a simple schematic?

 

[Ingineer]

Yes, that mechanical GE DPDT timer will work fine. Connect the common leads to the EVSE, the NC leads to the EV meter hots, and the NO leads to your house panel hots. When the timer is "on" it will move the EVSE load to the house.

If you are using one of our units, there is nothing special you have to do, the transfer will be seamless even while charging.

Most other EVSE's should be ok as well, but it would help to try and verify you have the correct legs together. (put a meter between each NO and NC terminal, and you should have under a few volts, if not, then reverse one set of hots.

-Phil

 

[davewill]

My utility has a similar 'experimental electric vehicle' program and there is absolutely nothing in the terms of service that I could find that says I can't charge on normal residential rates if I wanted to. ...

Yah, I know the power police aren't going to come and get him, and I'm probably just picking nits. I just see a benefit to playing it more kosher.

 

[DaveEV]

Yes, that mechanical GE DPDT timer will work fine. Connect the common leads to the EVSE, the NC leads to the EV meter hots, and the NO leads to your house panel hots. When the timer is "on" it will move the EVSE load to the house.

If you are using one of our units, there is nothing special you have to do, the transfer will be seamless even while charging.

Most other EVSE's should be ok as well, but it would help to try and verify you have the correct legs together. (put a meter between each NO and NC terminal, and you should have under a few volts, if not, then reverse one set of hots.

What Phil said, but to make wiring simpler - L1/L2 is one hot leg. As Phil says - it's helpful to make sure you have the same hot legs on NO/NC and NO2/NC2.

Using the labels as indicated in the QuickStart guide:

TIMER1=L1 house
TIMER1=L2 house
COM=EVSE L1
COM2=EVSE L2
NC=L1 EV meter
NC2=L2 EV meter
NO=L1 house
NO2=L2 house

You can use a 4" and a 7" jumper between TIMER1/NO and TIMER2/NO2. As indicated, you should be using 8GA wire, though you may find it easier to use thinner wire (the QuickStart guide lists appropriate minimum wire gauges) but then you'll have to reduce the size of your circuit breaker feeding the timer accordingly.

 

[mitch672]

You could do ths with "OpenEVSE" as well, since you can control the relay, you could just build it with 2 separate AC inputs, controlled by the OpenEVSE code (and 2 relays), OpenEVSE is based on Arduino, so the code is easy to work on, and you can get various communication modules easily added, such as Bluetooth, Ethernet, etc. it all depends on how much you want to customize it.

 

[Ingineer]

What Phil said, but to make wiring simpler - L1/L2 is one hot leg. As Phil says - it's helpful to make sure you have the same hot legs on NO/NC and NO2/NC2.

Using the labels as indicated in the QuickStart guide:

TIMER1=L1 house
TIMER1=L2 house
COM=EVSE L1
COM2=EVSE L2
NC=L1 EV meter
NC2=L2 EV meter
NO=L1 house
NO2=L2 house

You can use a 4" and a 7" jumper between TIMER1/NO and TIMER2/NO2. As indicated, you should be using 8GA wire, though you may find it easier to use thinner wire (the QuickStart guide lists appropriate minimum wire gauges) but then you'll have to reduce the size of your circuit breaker feeding the timer accordingly.

Yes, this is correct, but the Quick-Start guide has bad advice of linking the high-current through the jumpers to the timer motor. Connect the House L1/L2 to the NO1/NO2 terminals respectively, then run 2 jumpers from there to the 2 timer terminals (which one goes to which doesn't matter). Be absolutely sure to set the dip switches for 240v before restoring power!

-Phil