Date:         Thu, 17 Aug 2006 16:25:20 -0700
Reply-To:     "Mike \"Rocket J Squirrel\" Elliott" <camping.elliott@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "Mike \"Rocket J Squirrel\" Elliott" <camping.elliott@GMAIL.COM>
Subject:      Re: Any solar gurus out there?
In-Reply-To:  <000001c6c122$e0706930$6400a8c0@MASTERPC>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

What Dennis said.

I have a pair of 45W BP panels that I extend out on 40' of 6-gauge wire
to wherever the sun is shining. The output of the panels feed a Blue Sky
2000e solar controller which charges a Group 27 100 a/h battery stashed
under the rear seat. This arrangement runs our Norcold refrigerator,
evening fluorescent and halogen reading lighting, a little nachtmusik,
and a DVD for our viewing pleasure. When morning comes, the battery is
about 30% depleted. By late morning, the panels have charged it back to
full capacity. I reckon I got plenty of battery and panel for our needs.

A handy-dandy +/- 10A analog ammeter gives me a quick-glance check of
current in/outflow, while a fancy-pants Xantrex Battery Monitor, which
is trainable to count coulombs (amp hours) in/out of the battery and
trainable to know what conditions /I/ consider the battery to be fully
charged. It resets itself to "full" when those conditions are met. For
me, I have told it that when the battery voltage is greater than 14.1
amps, and the charge current is less than 1 ampere, for four minutes,
the battery is full. The solar controller has been told to take the
battery up to 14.2 volts, at which point it tapers the current as needed
to not exceed that voltage. It's a tweaky system, but it's fun for me.

Mike "Rocket J Squirrel" Elliott
71 Type 2: the Wonderbus
84 Westfalia: Mellow Yellow ("The Electrical Banana")
74 Utility Trailer. Ladybug Trailer, Inc., San Juan Capistrano
KG6RCR



On 8/16/2006 3:58 AM Dennis Haynes wrote:
> 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
>>
>>
>
>