Your really need to determine your actual requirements and first determine
required battery capacity. How long will you regularly be staying in one
place? Do you really need a week's capacity? What are you planning to run?
Maybe a micro-generator makes sense!

One thing about battery charging is the process is not linear, and to reach
100% state of charge (SOC) you need to return 107% of the power used. A well
designed system should be based on keeping the battery between ~40 to 80~
SOC. Periodic full and equalizing charges can then be performed to maintain
the battery. Keep in mind the battery rated capacity and real world
especially at half life are not the same.

The alternators charging capacity is based on the set voltage and the
batteries "charge acceptance". The larger the battery, the more amp/hours it
will absorb at the fixed 13.8 volts. Somewhere around 15 to 35 amps from 20%
to 70% SOC is typical. A voltmeter will tell if the alternator is keeping up
or if you need to provide some means to increase idle rpm. If considering a
high output alternator, keep in mind that these produce less current at idle
rpms.

Dennis

-----Original Message-----
From: Andy Highland [mailto:andy@420.AM]
Sent: Wednesday, August 16, 2006 1:10 AM
To: Dennis Haynes
Cc: vanagon@GERRY.VANAGON.COM
Subject: Re: Any solar gurus out there?

I have been going about it backwards, trying to choose a system based
on the charging documents at

http://www.odysseyfactory.com/support.htm

The battery is a PC1200 (44Ah).

On a recent trip I discharged the battery in 2 days. So, I would
estimate that my usage is about 150Ah per week. I need to find a
system that will keep up with that rate of usage, and will meet the
minimum requirements of the odyssey PC2100. The best solution seems
to be an 80W panel, but based on the odyssey docs, that will not
bring the battery out of deep discharge. I guess that's when I'll
start the engine. Which begs another question, how much current does
the alternator put out with the engine at idle?

thanks,
andy

On Aug 15, 2006, at 3:47 AM, Dennis Haynes wrote:

> Bring a lot of money. Basically, you will need 150 watts and a charge
> controller. You are looking at spending ~$1,000 for this much power
> and that
> will only be available on sunny days. Then you need some good
> batteries to
> store that power to make it worthwhile. Why do you need that type
> of juice?
>
> Dennis
>
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
> Behalf Of
> andy highland
> Sent: Monday, August 14, 2006 9:00 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Any solar gurus out there?
>
> I'm hoping to acquire the components for a solar charging rig rather
> quickly and could use some help. I want to come up with a rig that
> will
> provide 10A at 14.3V.
>
> Thanks,
> -andy
>