[RE-wrenches] Direct PV-EV charging: possible?

[Parrish, Peter]

I am currently researching this opportunity from the perspective of having "Solar Carports with EV Charging". The idea is to have about 2.5 kW-dc produce about 10 kWh/d @ 240 Vac (avg over a year). They could also be set up with a specialized charge controller to handle DC charging. I want to pick the "sweet spot" first and was thinking the 240 Vac/L2 charging system would be my first choice.

Let's take the discussion off line. Anyone else who is interested is welcome. - Peter


Peter T. Parrish, Ph.D., Chair
Alternative Energy Department
College of the Canyons
17200 Sierra Hwy.
Santa Clarita, CA 91351
peter.parrish at canyons.edu
O: (661) 362-3888 C: (323) 839-6108



From: re-wrenches-bounces at lists.re-wrenches.org [mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of Allan Sindelar
Sent: Thursday, August 23, 2012 6:50 AM
To: RE-wrenches
Subject: [RE-wrenches] Direct PV-EV charging: possible?

Wrenches,
We have a customer who has built several EVs, and wants to eventually develop a business around them here. A few years ago we installed a GT system on his home. He has now moved and wants to install a system on his new home as well. This time, he'd like to develop a means by which to charge his EV directly from his array, avoiding the inefficiencies of inverting to the grid and then running a grid-based charger. 

I know of no way to do this, but then, I'm a veggiehead (drive an old Mercedes on waste fryer oil), not an EV aficionado. I suspect that there are folks out there trying to do this, as it's a logical objective. Can anyone suggest products, links, or websites for this customer to explore?

Here are his notes about this effort:
...this is essentially the idea. to use the EV as rolling battery backup to dual-purpose the investment in battery. The second plus is avoiding loss from two inversions dc-ac-dc, the third being relatively high-amp charge without buying another charger! and dual purposing the inverter to avoid cost of high-amp inverter only used for emergencies for a backup. 

The tech details of EV battery packs that are going to make this a challenge is the high voltage. The DIY pack running DC are going to be 120, 144, 156vDC nominal most commonly. Guys running AC motors and OEMs might run much higher.... closer to 300v. 

The charge controller or voltage limit switch needs to be user settable and fairly accurate (+/- 1 volt). The DIY people usually use a 'finish' voltage of 3.65volts / cell being 'done'. So for a 120v nominal system I would want to set the DC charge to come up to 139v and either shut down right then, or if it COULD just hold at 139v until amps drop or a specified time, that would be even better. 

I am planning to do a grid-tie system at my new house, and yes, the intent is to 'stub-in' capability to both quick-charge the pack direct from the DC side of PV if possible, AND use the car pack as night-time/emergency backup just to show its possible.... 

My little car has 12kWhr on board, one I'm working on right now will have 20kWhr onboard. 
Thank you in advance for any assistance.
Allan
-- 
Allan Sindelar
Allan at positiveenergysolar.com
NABCEP Certified Photovoltaic Installer
NABCEP Certified Technical Sales Professional
New Mexico EE98J Journeyman Electrician
Founder and Chief Technology Officer
Positive Energy, Inc.
3209 Richards Lane (note new address)
Santa Fe, New Mexico 87507
505 424-1112
www.positiveenergysolar.com