[RE-wrenches] Fwd: Car charging station without grid

[Gary Willett]

The current industry standards for Electric Vehicle (EV) charging 
stations use either a standard 120Vac or 240Vac feeder. The EV has its 
own internal charge regulator unique to the type and voltage of the 
battery bank used.

To my knowledge, here is no EV manufacturer that has a DC charging 
circuit connection.

Charging with DC is technically possible, but you are going to need a 
DC-to-DC converter (with its efficiency losses) that also has charge 
controller functionality. I don't know anyone that makes such a device. 
Plus, if the customer connects the EV to a non-standard method of 
charging, he's likely to void the EV's warranty since the external DC 
charger/controller would have to mimic the EVs internal charge regulator.

A possibility might be a SMA Sunny Island or a Xantrex 4024 with a 
minimally sized battery bank. The 240Vac output of the inverter would be 
dedicated to the EV charging station function. Sizing of the battery 
bank would depend on the current requirements of a fully discharged EV. 
The advantage of this approach is that the EV's internal charger would 
pull it's power from the sun when it's shining, and from the grid at 
night or on cloudy days. The Sunny Island or the Xantrex can be 
programmed to only charge from the grid when the rates are the cheapest.

Regards,


Gary Willett, PE
Gary at IcarusSolarServices.com <mailto:Gary at IcarusSolarServices.com>


On 7/14/2011 3:43 PM, Allan Sindelar wrote:
> Wrenches,
> I'm stumped as to the best approach for a customer who wants a 
> non-grid-tied, batteryless PV-powered EV charging station. See below, 
> from one of our salespeople. Any ideas?
> Thank you,
> Allan
>
> -------- Original Message --------
>
> Allan:
> Monday I sit down with an interesting fellow who sounds like a 
> potential good customer (has money and right enviro goals) - in SF.
> He brought up the idea of discussing a car charging station for future 
> electric car that:
>
>    1. stands alone, no grid connection
>    2. no batteries - he pictures his car is home most days - he parks
>       it and when the sun shines it gets charged directly
>
> Why that approach?
>
>    1. He is thinking this must be the most efficient conversion, i.e.
>       directly without batteries or line loss of electrons to and from
>       utility
>    2. Wants the car to function independent of dirty fuel/dirty electrons
>    3. He assumes less equipment; maybe less cost but the cost is not
>       important other than as example for others
>
> Issues I see:
>
>    1. All inverters that can produce the high voltage needed need grid
>       power or if off grid need batteries - know of anything stand
>       alone available?
>    2. Power or voltage fluctuation as panels see more or less sun; ie
>       hours of day or clouds, etc - what will be the output from inverter?
>    3. Without tieing into grid investment in PVs (both his financial
>       and the embodied for manuf.) gets wasted when car fully charged
>       or car not home and sunny.
>    4. Is total amps output in peak sun even going to meet the charging
>       requirements? ie takes 10 days to recharge instead of 4 hours -
>       or overly massive system to match rate of charge?
>
> Your thoughts?
> Karlis
>
>
> *Allan Sindelar*
> _Allan at positiveenergysolar.com_ <mailto:Allan at positiveenergysolar.com>
> NABCEP Certified Photovoltaic Installer
> NABCEP Certified Technical Sales Professional
> New Mexico EE98J Journeyman Electrician
> *Positive Energy, Inc.*
> 3201 Calle Marie
> Santa Fe, New Mexico 87507
> *505 424-1112*
> _www.positiveenergysolar.com_ <http://www.positiveenergysolar.com/>
>
>
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