Great information, thanks Dennis
This goes in my Bentley for future reference 

Dennis Jowell
Scotch Hollow Farm
West Newbury, Vermont 

> On Dec 21, 2014, at 10:05 PM, Dennis Haynes <d23haynes57@hotmail.com> wrote:
> 
> 12 volts X 1 amp would be 12 watts. 
> 10 volts at 1 amp is 10 watts. So doing some algebra if you need 12 watts
> and only have 10 volts you need 1.2 amps. 
> 
> So you have 2-13 watt bulbs. 26 watts. There will be losses both in the
> inverter and the ballast for those lamps.  Let's figure we can get 90%
> between the two. 
> So to get 26 watts figure we really need 28.6 watts. 28.6/10.5=2.74 A/H. 
> Now let's say you want to run that 600 watt microwave. Again for losses add
> 10%, (yes this is a bit exaggerated but possible) you need 660 watts. If you
> only have 10.5 volts the inverter will need  62.86 A/H. 
> Now if you want to run this off a battery for any length the battery bank
> should be sized so that the draw is about 20-25% of the rated capacity (4-5
> hour). So you should be looking at a 240 A/H battery bank for this job. 
> 
> Dennis
> 
> 
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> Dennis Jowell
> Sent: Sunday, December 21, 2014 10:50 AM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Solar collector
> 
> I have 2-F13T5CW fluorescent bulbs above the gallery area. They are listed
> at 13watts per bulb.
> I understand about the loses in the inverter. But confused with the below.
> "There are some loses in the inverter and as the battery discharges the
> inverter will try to run all the way down to 10.5 volts so that is why I use
> the 1 to 10 instead of 12 volts. "
> What does it mean " use 1 to 10 instead of 12 volts?
> 
> Dennis
> 
> Dennis Jowell
> Scotch Hollow Farm
> West Newbury, Vermont 
> 
> 
>> On Dec 20, 2014, at 6:08 PM, Dennis Haynes <d23haynes57@hotmail.com>
> wrote:
>> 
>> What size are those lights? The inverter draw will be proportional to 
>> the load placed on it. Figure 1 Amp/Hour for every ten watts. Watts = 
>> volts X amps. There are some loses in the inverter and as the battery 
>> discharges the inverter will try to run all the way down to 10.5 volts 
>> so that is why I use the 1 to 10 instead of 12 volts.
>> 
>> Dennis
>> 
>> 
>> -----Original Message-----
>> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On 
>> Behalf Of Dennis Jowell
>> Sent: Saturday, December 20, 2014 2:59 PM
>> To: vanagon@GERRY.VANAGON.COM
>> Subject: Re: Solar collector
>> 
>> Thanks Dennis for the info. I only use the inverter to run the 2 
>> lights over the sink when their is no shore power available. Does this 
>> still put that much load on the alternator?
>> 
>> Dennis
>> 
>> Dennis Jowell
>> Scotch Hollow Farm
>> West Newbury, Vermont
>> 
>> 
>>>> On Dec 20, 2014, at 9:52 AM, Dennis Haynes <d23haynes57@hotmail.com>
>>> wrote:
>>> 
>>> From the factory the Westy did not come with a dual battery set up. 
>>> What was there was a relay controlled from the alternator 
>>> exciter/indicator light circuit wired so that the refrigerator would 
>>> work on DC power when the alternator was actually charging. Many have 
>>> used that set up to charge an auxiliary battery and for the most part 
>>> it somewhat works. The GoWesty instructions may be assuming you are 
>>> adding the 2nd battery and solar system at the same time so the 
>>> recommendation for the kit. You should be able to connect the solar 
>>> panel system to your house battery leaving everything else as is.
>>> 
>>> Since you have that 800 watt inverter keep in mind that at full load 
>>> you are looking at some 80 amp/hour draw. While running the 
>>> alternator will try to be the source and with a relay inter-connect 
>>> the chassis battery will also get involved. All the wiring and the 
>>> relay needs to be able to support this load. I would suggest #6 or #4 
>>> and a 100 amp relay. Yes all the way to the alternator.
>>> 
>>> Dennis
>>> 
>>> 
>>> -----Original Message-----
>>> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On 
>>> Behalf Of Dennis Jowell
>>> Sent: Saturday, December 20, 2014 9:03 AM
>>> To: vanagon@GERRY.VANAGON.COM
>>> Subject: Solar collector
>>> 
>>> I just received my GOWESTY solar kit to add power to my auxiliary 
>>> battery and read the instruction install sheet. The recommended 
>>> install procedure is to purchase  the GOWESTY auxiliary battery kit.
>>> My 1988 Westy came with the factory  auxiliary battery hookup already 
>>> installed. My question is do I really need the GOWESTY add on or use 
>>> the factory kit on board already. I've been using the 2nd battery for 
>>> years. I have a battery charger, 800 watt inverter, and my truck 
>>> fridge running off the 2nd battery with no problems but I would also 
>>> like to add my stereo to the 2nd battery next. Does anyone have any
>> experience with the solar kit. Any help would be appreciated.
>>> 
>>> Dennis
>>> 
>>> Dennis Jowell
>>> Scotch Hollow Farm
>>> West Newbury, Vermont