Help! Simple Solar Information Needed SOON

 Solarites,

I am building a solar recumbent tricycle to take to the
Burning Man art festival in the Nevada desert.  (and I
leave in about 3 days, which is why I would really
appreciate some feedback SOON...)

The trike is built.  I motorized the trike using parts
from a 24v electric bike system (24 volt sealed lead
acid battery, motor, and speed control).

I have 4 BP Solar PV panels, each of which say they
generate open circuit voltage of about 21 v.  I have
a Xantrex C35 charge controller which can handle 12v
or 24v systems.  Wiring up the PV panels, charge
controller, and battery looks pretty straightforward.

Here is my question:

How many PV panels do I need?  As I said, the open
circuit voltage is right around 21v.  It also says
the loaded voltage is about 12v.  If I set the Xantrex
chg controller for 24v, so it can charge my 24v
battery, must I connect two of the PV panels to the
chg controller for it to work?  (presumably I would
just connect 2 panels in series to the controller)
Or would the charge controller still work (in 24v
mode) if I only connect one of the PV panels to the
chg controller?

I ask this because it would be MUCH easier to fit one
panel on the trike.  If I have to, I can fit two on
there, but it would be much more difficult.

I read the documentation for the charge controller
very carefully but I could not find the answer.

I am new to this cool solar world so please forgive
the newbie question.

Thanks!

  Solar Triker wrote:
...

A PV panel designed to charge 12V batteries will have
an open circuit voltage around 21V. The voltage of the
panel must be higher in order to charge the battery.
You need to wire them in series (2 panels) for your
24V charge controller to charge 24V batteries.

Anthony

 Anthony,

I was afraid of that...  but thank you!  That's what I needed to know.

Damon