RE: PV: Questions about Solar charging my EV

[Robert Warren <robertwarren@mail.com>]

Dear Matt,
First, we would have to know basic questions about
your EV. What is the battery size and type, both
in voltage and in mp hours?  I assume you do have
an electric charger, that you plug into a wall
outlet at your home when you park?
Tell us about your EV. Also, how do you use it,
how many Km you drive per day, and whether it is
city driving (probably yes, if you are in UK)?
Generally, photovoltaic panels are pretty
expensive, and you can expect to pay around $6.00
US /watt for PV panels, or maybe less if you get
them in a large quantity. A large enough array to
supply all of your driving needs could cost as
little as $1,500 US (I guess that is around  938
quid), if you only drive one or two Km /every
other day. Or it might be $10,000 or more if you
are doing some serious commuting. I just put in a
seriously large system here in the US for a
pharmacist, who spent $40,000  for the PV modules,
alone. The balance of the system, installed, was
around $80,000!
Here is a photo, if you press your attachment
button.
For example, if you bought 250 watts of PV panels,
and get an average 4 hour day, you are charging 1
KW/Hr/day. Roughtly, one kilowatt hour is equal to
about 1 horsepower exerted over a one hour period.
A motorbike might get by with only needing 1 Hp,
but a car, due to all its extra weight and the
weight of the batteries, may need a 20 HP engine.
But if you only drove it for 5 minutes, you have
used up one days' supply if you only have a 250
watts of PV. Sounds pretty discouraging, doesn't
it?
Another way to look at it, though, is that since
you made the effort to buy an electric car, is
that you are eliminating the pollution which would
be added to the air, that day. True, you are using
electricity.
It is in the large scheme of things cleaner, which
is why the State of Calif. has legislated that 1
or 2% of all new cars being sold be zero emmission
vehicles.

The basic formula is, if you want to charge your
batteries (if they are wet cell lead acid
batteries) at a C-20 rate if you want them to last
a long time. A C-20 rate means you charge them
slowly over a twenty hour period to not over heat
them or boil off too much electrolyte. If you know
your battery bank is 200 amp hours, then C-20 is a
10 amp charge rate. However, if this is your basic
strategy, which works fine for a house that isn't
going anywhere, it means that in the UK you would
have to wait five days before you could drive your
car again, because you only get around four
hours/day of good charging for most of the year,
excluding winter, when you get a lot less.
The accepted rate for EV's is a C-10 rate, which
is more like what the plug in charger does, as you
leave it plugged in overnight.  This would be a 20
amp rate for the 200 amp hour battery examply,
above. This is still a couple days with the sun,
so it is also a bit inconvenient. Then, about once
a month, you want to oversharge them a little bit,
which is called "equalizing" to ensure that any
low cells also get fully charged up.
However, it is still a nice thing to have a
minimum of a 40 watt panel to be able to do a
trickle charge on your batteries if the car sits
around unused for a few days, like when you leave
it at the airport while going off on a trip. This
can really make a big difference, as all batteries
have a small self-discharge loss when they are
just sitting around, even new ones in the store,
before you take them hime. So, I do suggest yuo
have at least one solar panel in your car to do a
trickle charge. However, even here, there are
problems.  While a starting battery on a
traditional gas guzzler uses only one 12 volt
battery, it is likely that the car has a 48 volt,
or even a 96 volt or 120 volt battery system. Then
it would take however many multiples of 12 volts
or PV panels wired in series to even provide a
trickle charge. This array of modules in series
would have to be permantly affixed to your roof.
Now, one day, we will be seeing a lot of PV arrays
on top of car ports and filling stations. BP Solar
has started to do this. But even BP Solar, with
all their money, for right now, will only be using
the electricity to run their pumps, lighting, and
cash registers; but certainly not for charging
EV's.
I suggest you look at the web site for Home Power
Magazine www.homepower.com
as they have a wealth of information about
batteries, and a fair amount of the magazine is
devoted to EV's. The editor and publisher, Richard
Perez, is a world authority on batteries, and
author of The Battery Book.
Plus, they have for the last few years had regular
columns by the EV world authorities, Mike Brown,
and Shari Prange. Most of the Home Power Stuff is
available for download, but be forewarned, it
would take forever to download. Better to buy
their back issues on CD-ROM.

Another really good source, which I recommend with
some partiality, as I have worked as a solar
consultant with this group for the past three
years, is Rocky Mountain Institute. They are not
pushing Electric Cars at all, they are doing
something much, much better: re-inventing the car,
with the HyperCar. Honda has just released their
first one, this year, with many more to come from
various manufacturers.
Go to http://www.rmi.org/hypercars/
Another alternative transportation resource, which
I contributed to, is the page of an interesting
group in Hong Kong,
http://members.tripod.com/journey_to_forever/ethanol_robert3.html
There are really a lot of EV sources on the Web,
though, if you look around. I am sure others in
the PV Users/s group will contribute their
favorites to you.
Can you tell us a little about the Center for
Sustainable Construction, where you work? Do you
have a web site?
Gosh, I wrote a bit, here, and all you had was a
one liner question. Did I cover what you wanted to
know?
Regards,
Robert Warren

Questions about Solar charging my EV

[Matt is not on the EV, AE, PV Lists. Please copy
him on your response]
--[edited]
From:        "Thomas, Matt" <ThomasM@bre.co.uk>
Subject:        electric vehicles
Date:        Thu, 13 Jan 2000 12:00:58 -0000

I request information and experiences from people
on Trickle charging
and integrated PV (solar panel) cells on Solar
Electric Vehicles?
Many thanks in advance.

Matt Thomas  ThomasM@bre.co.uk
Centre for Sustainable Construction
Building Research Establishment
Garston, Watford WD2 7JR
Tel :+44 (0)1923 664866    Fax:+44 (0)1923 664084
www.bre.co.uk
--

-*Dear matlstice.crest.org/

------Original Message------
From: Bruce {EVangel} Parmenter
<BruceDP@iname.com>
To: "ae@sjsuvm1.sjsu.edu" <ae@sjsuvm1.sjsu.edu>,
"ev@sjsuvm1.sjsu.edu" <ev@sjsuvm1.sjsu.edu>
Sent: January 14, 2000 7:00:46 PM GMT
Subject: PV: Questions about Solar charging my EV


Questions about Solar charging my EV

[Matt is not on the EV, AE, PV Lists. Please copy
him on your response]
--[edited]
From:        "Thomas, Matt" <ThomasM@bre.co.uk>
Subject:        electric vehicles
Date:        Thu, 13 Jan 2000 12:00:58 -0000

I request information and experiences from people
on Trickle charging
and integrated PV (solar panel) cells on Solar
Electric Vehicles?
Many thanks in advance.

Matt Thomas  ThomasM@bre.co.uk
Centre for Sustainable Construction
Building Research Establishment
Garston, Watford WD2 7JR
Tel :+44 (0)1923 664866    Fax:+44 (0)1923 664084
www.bre.co.uk
--

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