Planning for another EV - Charging /EVSE question

[Luckyduckie]

We've had the Rav4EV for about 6 monhs (11k miles) and very happy with the experience so far. We've installed 5,75 kwh solar on the roof, are we're especially glad about skipping all those trips to the smelly gas station! I'm thinking about replacing our 2004 BMW 545 with another EV ( maybe model X if the price is right). I like to plan ahead, so I'm wondering what's the best strategy going forward? Do I get a second EVSE or ??? Currently, I drive the Rav4 in the mornings and my wife drives in the afternoon. We average about 72 miles per day and takes 3-4 hours to charge each night. Do I need to worry about overloading the elecrical panel if I have two EV's charging at the same time? Any suggestions or recommndations?

Thanks

 

[smkettner]

Get the specs on the Tesla wall connector and have an electrician review what can be done.
Your solar installer might be able to give an answer over the phone.
If you have an open slot for a 50a breaker and a 200 amp main panel you should be fine.

 

[fooljoe]

If I were you I'd just get another Rav while they're still available. I charge 2 EVs every night (Rav and Leaf) on a 125 amp panel and it works out fine. If there is a concern about overloading, you could just set their charge times so they're unlikely to both be charging at the same time, and/or you can use adjustable EVSEs (like openEVSE, juicebox, or Versicharge) to slow down charging, as I'm sure you don't need the full 40 amps for each to stay within your off peak window.

 

[miimura]

Do I need to worry about overloading the elecrical panel if I have two EV's charging at the same time? Any suggestions or recommndations?

If you have a licensed electrician do the installation, you don't have to worry about overloading anything because it should not be possible. If you want an assessment from the forum, you need to post a picture showing all the breakers in your main electrical panel and any sub-panels.

 

[Luckyduckie]

Thanks for you relplies.

Yes, I would definetly use a licensed electician.

Those of you who have two EV, do you have two EVSE's or is there some way to get by with one? And if I have two EVSE's can I use use it on one EV and charge twice as fast?

I do like the Rav4, but not enough to get another one. The best reason I can see for getting the Tesla model X or S would be for the longer range and supercharger for longer trips. I want to able to make a trip out of the bay area and not hear the wife and kids ask "are we done charging yet!"

 

[miimura]

Those of you who have two EV, do you have two EVSE's or is there some way to get by with one? And if I have two EVSE's can I use use it on one EV and charge twice as fast?

I do like the Rav4, but not enough to get another one. The best reason I can see for getting the Tesla model X or S would be for the longer range and supercharger for longer trips. I want to able to make a trip out of the bay area and not hear the wife and kids ask "are we done charging yet!"

You can get by with one EVSE if your single charge range is sufficient to charge every other day or you can charge them sequentially because your electricity price does not vary by time of day.
Each EV only has one charger inlet and one on-board charger, so you can't connect more than one EVSE. Just get an EVSE and electrical circuit that can fully supply the car's on-board charger. For the RAV4 EV and a Tesla with a single charger, that is a 40A EVSE like the Leviton EVB40, Clipper Creek CS-60, or Tesla Mobile Connector. A Tesla with dual chargers can take twice the power and charge twice as fast, but you will need to use the Tesla High Power Wall Connector (HPWC) or Clipper Creek CS-100. Both of those require a 100amp breaker. However, unless you foresee that you will have a long drive, come home and then have to go back out again after only a short time, you don't really need to put in an EVSE that big. It would be better to just put in two 40A EVSEs so that you can just plug in both the cars and let them charge overnight on off-peak rates.

 

[fooljoe]

Those of you who have two EV, do you have two EVSE's or is there some way to get by with one?

I have two. I used my EVSEupgraded Leaf charge cable plugged into an old dryer outlet in my garage for a couple years, then when I got the Rav I installed a 14-50 outlet on the side of my house by the driveway and plugged a CS-60 into that. So my wife parks the Leaf in the garage and I park the Rav in the driveway. I'm sure you could get by with one EVSE, but it'd be a big pain. And if you're on time-of-use metering (and you really should be if you're not already) it would be pretty unworkable unless you don't drive much or have an EV with a ton of range and can charge every other day. Getting up in the middle of the night to unplug one car and plug in the other just doesn't seem fun.

And if I have two EVSE's can I use use it on one EV and charge twice as fast?

In theory yes, but not without some major modifications. You'd have to install a second charger and J1772 inlet on your car to do this, which several Leaf drivers have done, and has been talked about for the Rav, but you can't yet buy a stock EV that comes with two charge inlets. The Model S is available with dual chargers, but not dual inlets, which makes it an incredibly worthless option IMO.

The best reason I can see for getting the Tesla model X or S would be for the longer range and supercharger for longer trips. I want to able to make a trip out of the bay area and not hear the wife and kids ask "are we done charging yet!"

If you can afford a Model S what are you waiting for? Obviously it's a much superior car, but it's hard to ignore that the Rav is 1/3 the cost. And since the Model X still isn't out yet the Rav is the only electric SUV out there if that's what you want.

The reason I say get the Rav now is the current deal's good and come the end of the year they won't be produced any more. Then when the lease is up the Model X and/or Model E should be available and perhaps more budget-friendly. And as far as those long trips, you can always just rent/borrow a gas car so you don't have to worry about lengthy charging times.

 

[arnolddeleon]

I concur with fooljoe, you will want two charging stations. We've had two EVs for almost 3 years with two charging stations. Properly installed with a properly sized panel you won't have an issue. It is possible to get a Tesla with twin 10kW chargers and since the RAV4-EV comes with a 10kW charger it is possible to end up with charging configuration that would be difficult to power with most residential services. OTOH you are not required to have your charging stations be the largest that the vehicles support.

FWIW I have a Blink on a 40A circuit and CT-500 also on a 40A circuit. I have 200A main panel, most of my house circuits are on subpanel so over subscription is reduced on the main panel. I have an energy monitoring system so I have a good sense on peak simultaneous load (less than 50% of that the panel can support). I will be adding installing a third EVSE, an EMW JuiceBox on a 50A circuit. The third EVSE will allow me to charge the RAV4-EV at the full rate that it supports. The new location will be better located for the rear port of the 2012 RAV4-EV. I'll probably retire the Blink from active duty.

arnold

 

[davewill]

This fellow sells the parts to build a "Hydra" which splits an EVSE into two plugs, and dynamically apportions the power between one or the other or both depending on how many cars are plugged in and whether they're actively charging.

http://code.google.com/p/open-evse/wiki/Hydra

Chris Howell (the creator of OpenEVSE http://code.google.com/p/open-evse) has also done two+ headed EVSEs, but I don't know if he's published the details.

That said, these options will likely cost more than simply having an electrician run a second circuit and installing a second EVSE.

 

[fooljoe]

The Hydra idea is pretty cool - although it's really meant to split the output of a host EVSE like a public charging station, while in this case a 2-headed EVSE would probably be preferred. Of course that only works if it's physically possible to park and plug in 2 cars at the EVSE.

these options will likely cost more than simply having an electrician run a second circuit and installing a second EVSE.

Actually an openEVSE, even the 2-headed variety, should be much cheaper than almost any retail EVSE, and if installing a 2nd circuit would involve a long run that could be pretty costly itself. Although you'll definitely be paying in terms of time if not dollars...

There's a guy over at the Leaf forum (GlennD) who makes and sells openEVSEs, and could probably cobble together a 2-headed one for you if you're interested.

 

[jspearman]

We've been fine with just one EVSE. We're a year into our two Plug-in household and no issues so far. I charge my wife's RAV at night and then I charge my Volt during the day. Not everyone can do that, but works great for us, and saves a lot of money on wiring and a new EVSE. You can also trickle charge one if it doesn't travel very far during the day.

 

[TonyWilliams]

I don't know your electric needs in the house, but if you can, just put a 50 amp circuit with a 40 amp EVSE for the Rav4 and 100 amp circuit with an 80 amp EVSE for the Tesla.

If you can't handle that electric load, then two 50 amp circuits will charge both cars from empty to full in eight hours or less with 40 amp EVSE's.

If you're really pressed for electrical needs, just use two 40 amp circuits with two 30 amp EVSE's, and so on. Yes, there are 25, 24, 20 amp, 16 amp and even 12 amp EVSE's.

I would absolutely use two J1772 plug on the two EVSE's so that either car can charge in either spot. Tesla can charge on J1772 with a supplied $95 adaptor.

 

[nsayer]

The Hydra is now available as a standalone EVSE variant. You do have to build it yourself, but fully assembled logic boards are available, so no soldering is required.

The standalone variant trades the inlet handling circuitry for a GFI and a real-time clock chip. The firmware has day-of-week timer scheduling for those with ToU tariffs and optional automatic DST switching.

For those who may want high powered plugs, a contactor adapter board is available to drive line powered contactors.

 

[agleung]

We are planning to install solar panels on the roof top this summer. Is there a guide to estimate the additional electricity generation required if I plan to drive 1000 miles per month on the RAV4? In other word, how much bigger system in kW I would need to add to my existing estimate? On the other hand is upsizing the solar system not warranted since we will be switching to TOU and only charging after midnight (I believe 9 cents per kWh) and therefore making the return on investment duration too long? There is also an Electric Vehicle Plan where it is 0.11 / kWh from 9pm to 12 pm. Thanks.

 

[smkettner]

We are planning to install solar panels on the roof top this summer. Is there a guide to estimate the additional electricity generation required if I plan to drive 1000 miles per month on the RAV4? In other word, how much bigger system in kW I would need to add to my existing estimate? On the other hand is upsizing the solar system not warranted since we will be switching to TOU and only charging after midnight (I believe 9 cents per kWh) and therefore making the return on investment duration too long? There is also an Electric Vehicle Plan where it is 0.11 / kWh from 9pm to 12 pm. Thanks.

Sounds like SCE? Where are you located?
The TOU benefit will depend on your usage schedule. The air conditioner really needs to be off from 10a to 6p and other use curtailed as possible during weekday on peak hours.

Otherwise 3.5 miles per kWh gives 285 kWh per month, 3428 kWh yr.

 

[drmanny3]

We originally sized our solar panels to cover about 70% of our electric usage. The idea was to stay in tier one or two at most. That actually worked initially. I think we also cut back on electricity use by changing out old electric bulbs for the newer types like Leds. When we added the leaf we ended up consuming a lot more electricity. In May of 2011 we paid $318 for the previous year plus the typical $1 to $2 monthly service charge. We got the Leaf in May of 2011. In May of 2012 we paid $350 for the year. In May of 2013 we paid $525 for the year. In May of 2014 we paid $230 for the year. In the last year we had both the 2011 Leaf and the Rav4EV (purchased on Jan 24th 2014). So when you look at our electric bill over the last few years we managed to almost charge the cars for free. Our first year bill without any electric vehicle cost us $318. When we got our 2011 Leaf later that month we immediately shifted to the TOU. I think our super off peak usage was about 300 to 350 kwh each month. We often would get a credit during the day because of the solar panels. As was mentioned above you need to keep electric use to a minimum during the day up to 6pm. Otherwise instead of a big credit you will get a big bill. I can tell you there were a number of days where we suffered until 6 pm when we could then turn on the air conditioner. I also should mention that we upgraded the insulation in the attic as well as upgraded our forced air/air conditioning systems. Everything is pretty energy efficient and that makes a big difference. The Rav4EV uses more juice for the same mileage than our Leaf delivered, but it is still working out nicely. So to recap we went from about $2400 per year in electricity to about $200 to $500. The solar panels from SolarCity cost us a one time lease payment of $10,414. We were one of the last homes that used thin film technology panels. They tend to be lower in efficiency but work even when the day is cloudy. Our system consists of 68 panels in three sections. Our solar system is rated at 4.6 kw AC or 5.1 kw DC. I had originally estimated our payback at 4 1/2 to 5 years. If you add the use of an electric car then our payback occurred probably in the 4th year. I could figure out exactly what the Leaf cost us each month with and without the panels but this is seat of the pants guess. This does not cover the savings in gas as we went from $160 month for the Prius to about $40 a month. I also considered a second meter but found the requirements of adding the second panel and connections a real pain and high cost. In the end the current 12 midnight to 6 am is almost as cheap as the second meter, just not as much charging time. Hope this helps.
Manny

 

[fooljoe]

Otherwise 3.5 miles per kWh gives 285 kWh per month, 3428 kWh yr.

That's probably a bit too optimistic. You'd be hard-pressed to average 3.5 miles/kwh at the dash - I think the average is closer to 3; and that's neglecting the ~80% charging efficiency. If we call it 3.2 at the dash then that means about 390 kwh / month from the wall. I'd round it up to 400 to be conservative.

As smkettner alluded to, how much solar you need to cover this depends heavily on your usage pattern. With SCE's TOU rates, you can charge for 9-9.5c/kwh if you keep it all between midnight and 6am (super off peak), while your solar production will generate credits mostly on-peak, and off-peak on weekends and outside of 10am-6pm on weekdays. Once you get into tier 2, the on-peak rates get as high as 34c/kwh, while in tier 1 off-peak your solar might be worth only 16c/kwh. So you might figure that on average you can charge with about 2-2.5x your solar production and not be adding any cost to your bill.

For reference, my 3.84 kw system has generated 15.2 Mwh lifetime over 26 months, so about 585 kwh/month, or 152 kwh/month/kw. So if we assume your system will produce similar to mine, you'd probably want at least 1 to 1.5 extra kw to make sure charging the Rav is covered.

 

[miimura]

I agree with fooljoe - 400kWh/mo is about right for 1,000 miles per month on a RAV4 EV. My 4.32kW DC solar system made 6,035kWh in the last 12 months. So, my location, installation angles, and shading make the production less than fooljoe's at about 116kWh/mo/kW. I've never actually thought about it that way, but it makes sense as a way to account for all the factors I mentioned. Solar installers have the means to accurately estimate production ahead of time and they should be able to analyze your current bills and add the Off-Peak charging to meet your solar goals. I would shoot for 80% to 100% bill offset. Zero net energy is an admirable goal, but it extends the payback of the system considerably because you're giving energy to the utility with no return.

 

[Luckyduckie]

Zero net energy is an admirable goal, but it extends the payback of the system considerably because you're giving energy to the utility with no return.

Another reason to consider getting a second EV ... or maybe look into battery storage???

 

[smkettner]

I agree with fooljoe - 400kWh/mo is about right for 1,000 miles per month on a RAV4 EV. My 4.32kW DC solar system made 6,035kWh in the last 12 months. So, my location, installation angles, and shading make the production less than fooljoe's at about 116kWh/mo/kW. I've never actually thought about it that way, but it makes sense as a way to account for all the factors I mentioned. Solar installers have the means to accurately estimate production ahead of time and they should be able to analyze your current bills and add the Off-Peak charging to meet your solar goals. I would shoot for 80% to 100% bill offset. Zero net energy is an admirable goal, but it extends the payback of the system considerably because you're giving energy to the utility with no return.

Yes my usage estimate was a bit low. Also consider your miles may increase if you are shifting burden from another car to save fuel. My miles driven jumped at least 20% as the Subaru is now the gas hog.

My 3kW DC solar covers about half my usage but reduces the bill 80% due to the favorable TOU billing. This month my net usage is 470 kWh, cost is $2.
I advise installing enough to cover 50% to 80% of usage. My actual production is at least 10% more than estimated.