"Larry" wrote
Hope yours is a POWER boat....(c;
Sailing's awfully boring with no wind....

Mine's what you might call a hybrid. Got this fossil fuel unit on the back,
with the power of four horses.

Two questions... as the input I doubt would exceed the current used is
there any problem just hooking the panel direct to the house battery
without a regulator?
No problem 20 watt panel will not over charge batteries, make sure panel has
blocking diode, if not you need cheap charge controller.

How do I connect both batteries to the panel at the same time. By
connecting the panel to the "both" setting on the battery switch?
No quite, hook panel to one of the batteries preferably the house battery.
When you want to charge both set switch to "both".
If you connect panel to both or output terminal you risk supplying up to 22
volts to boat systems when battery switch set to "OFF".
In the "OFF" position the solar panel has no load except for boat systems
and the voltage rises... Tough on electronic items.


Jerry,
The thing to remember about solar panels is that they are rated at full
sunshine and aligned 90% to the sun. Seldom achievable on boats. So you have
to add more panels to make up the difference and allow for cloudy days when
the panels output is lower.
A better alternative on sailboats are wind generators.
http://www.windenergy.com/air_x_marine.htm
20 watt panel is too small to keep the batteries up but it will prolong the
length of time before charging required, and will keep batteries up for
bilge pumping, anchor light, etc. when away from shore power..
20 watt solar panel X 10hrs = 200 watt hours The math formula to figure out
how much power you need in watt hours, fridge only add more for other draws;
You didn't say what type of fridge you have, but lets assume its a 12 volt
compressor type. Compressor runs 20 min per hour X 24hrs = 8 hrs.
3.5 amps X 12 volts = 42watts X 8hrs = 336 watt hours
The minimum solar you need is 120 watt panel(s) for successful operation.
Using a factor of 3 times your load works well for solar panel sizing. Also
when using more than 30 watts of solar panel(s) you must use a charge
controller to prevent overcharging of batteries, they also double to prevent
the batteries from discharging through solar panels at night or no sun.
Solar panels
http://www.energyalternatives.ca/amazing/items.asp?CartId={4F957B5E-E989-4336-BEVEREST41F-FF137984BA59}&Bc=SHARP&Cc=110&Tp=&BrandName=Sharp+ Solar&CatName=Crystalline+PV+Modules
Solar charge controller
http://www.energyalternatives.ca/amazing/items.asp?CartId={4F957B5E-E989-4336-BEVEREST41F-FF137984BA59}&Tp=&iTpStatus=1&Cc=180
-OR- http://www.vdcelectronics.com/batter...solar_15a.htmr


"Jerry Atkiin" wrote in message
...
I just installed two 31 Optima batteries in my sailboat. I had thought
about installing a good size solar panel however we decide for the amount
of season we have in Michigan and the amount of motoring we do it would
probably not be worth the expense. However I have seen on EBay a 20 watt
portable panel that I thought might be handy to just hook up when
anchored
to minimize the amount of engine running time and if anything keep the
refigerator top up.

Two questions... as the input I doubt would exceed the current used is
there any problem just hooking the panel direct to the house battery
without a regulator?

How do I connect both batteries to the panel at the same time. By
connecting the panel to the "both" setting on the battery switch?

Jerry