Prius as UPS [RE-wrenches]

[Dick Ratico]

Carl,

I'm intrigued by the idea of using the Prius as a substitute for the usual
fossil fueled generator in a battery backup system. Here in VT / NH, where it is
not uncommon to go two weeks without much solar support, a generator, a backup
to the backup, becomes necessary.

The best fit for the Prius, might be as a means to eliminate that redundancy,
and to minimize the size of the Sunny Island's required 48V battery, especially,
as in your client's case, one supported by a 5kW array. The Prius would be used
more as a charging source, as it seems to be on the "priUPS" website, a very
interesting one by the way, mediated by an appropriate Sunny Boy inverter, which
is already designed to work with the Sunny Island. Perhaps the same Sunny Boy,
Boys, (Girls?) already in the system could be used, through a transfer switch
setup. It would certainly be a feather in SMA's cap to be able to offer this
option. It would also add momentum to the overall plug-in hybrid technology.

In this installation the DC voltage window in the SB5000 may or may not not
match the Prius' battery voltage. It has also been pointed out, that there are
likely other complicating factors as well, including the existing Sunny Boy
software. 

It seems to me the NEC does not address the situation of the high voltage Prius
battery (parked outside a residence) being connected to a grid-tied inverter,
also outside.

Dick Ratico
Solarwind Electric


Mick Abraham wrote:

"Carl Adams wrote:

"The customer is intrigued by the idea of using his Prius as the
battery bank. (for a Sunny Island under consideration).

Mick says: Amory Lovins' Rocky Mountain Institute had speculated about using the
"supercar of the future" in a manner similar to Carl's description. It's a keen
idea, but...

heres a link for info on the Prius batteries of various model years:

http://www.eaa-phev.org/wiki/Toyota_Prius_Battery_Specs

Note the high voltage/low ampacity characteristics, and remember that Sunny
Island is designed for a 48 volt (nominal) battery. The Prius uses hundreds of
"flashlight sized" batteries all wired in series. One should not (even
temporarily) connect these cells into parallel strings at lower voltage, because
ni-mh is widely known to be unsuitable for charging strings of cells connected
in parallel.

The person behind the "priUPS" website that Carl referenced got hold of an
"unterruptible power supply" designed for high voltage batteries in order to get
an inverter for high voltage DC input. Here's a link:

http://www.priups.com/misc/update-2005-06-1.htm

A high voltage UPS seems more appropriate for the Prius battery string than a
Sunny Island, except for the code problem of a high voltage battery connected to
a building, and except for the problem of trying to properly charge costly ni-mh
cells using a UPS that was actually intended for lead acid...

One more point: Since the Prius cells are only rated for 6.5 amp hours, 100%
discharge would provide less than two kilowatt-hours of stored energy before the
hybrid engine would need to crank up.



Mick Abraham, Proprietor
www.abrahamsolar.com"


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