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

Jerry Atkiin wrote in news:Xns991CA281EDD1tayana272
@216.168.3.44:

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?



Not a 20 watt panel like you're looking at. 20 watts is NOTHING! 20
watts is an anchor light. Only problem with that is it's only 20 watts
at NOON on a bright, sunny day with no clouds and no obstructions shading
the panel. It's only 20 watts for a couple of hours. The anchor light
is from dusk to dawn, 10 hours to 14 hours.

Charging the battery with a 20 watt panel and the tiniest fridge running
off the batteries will kill the battery 2 hours later than without the 20
watt panel....if the sun is bright, of course.

We need KILOWATT HOURS, not watt hours....Big difference!

Larry
--

"Larry" wrote Charging the battery with a 20 watt panel
and the tiniest fridge running
off the batteries will kill the battery 2 hours later than without the 20
watt panel....if the sun is bright, of course.

We need KILOWATT HOURS, not watt hours....Big difference!


Larry,

What you say is true if the boat is continually in use, like a liveaboard.
Lets say it puts out, on average 1amp for 8 hours on a nice sunny day in
Michigan. If the boat has a fridge, it probably draws about 2.5A on
average, so the panel will provide 40% of this for 1/3 of each day. Total
is 8 Ah/day or about 16 minutes motoring (on our boat).

But, if the boat sits at dock a good part of the time, the 20 Watt panel may
do some good. Lets say 6Ah/day for 5 days between weekend cruises. This
will put back 30Ah, or about 30% of what is needed to recharge a 200Ah bank
that is 50% discharged.

I have been thinking about installing one 80 or two 40-Watt units. These
would have capacity to recharge our 200Ah bank between cruises. When it is
operating at peak while cruising, it will put out the 5Amps that the fridge
draws when running. It will need a regulator and I would connect it to the
input of our battery combiner (which is actually the alternator output).

Still need to do some research on which unit(s) to buy.

"Duffer" wrote in news:hgwXh.17676$Uq.6520
@read2.cgocable.net:

Still need to do some research on which unit(s) to buy.


A windcharger with a charge regulator. Then it doesn't matter how much
power you use....The wind always blows....24/7 if the damned boat is
anchored out so it can drag...(c;

You don't have to sit in the dark with the windcharger.....

Larry
--

Larry wrote:
"Duffer" wrote in news:hgwXh.17676$Uq.6520
@read2.cgocable.net:

Still need to do some research on which unit(s) to buy.


A windcharger with a charge regulator. Then it doesn't matter how much
power you use....The wind always blows....24/7 if the damned boat is
anchored out so it can drag...(c;

You don't have to sit in the dark with the windcharger.....

Larry
But you have to turn the sound up on the stereo!

krj wrote in news:weSXh.13859$vD4.1013@bigfe9:

But you have to turn the sound up on the stereo!



If you play your cards just right, she'll be makin' too much noise up in
the V-berth to hear the windcharger....(c;

If all you can hear is the windcharger, you'll know you screwed up!

Larry
--

"Larry" wrote in message
...
"Duffer" wrote in news:hgwXh.17676$Uq.6520
@read2.cgocable.net:

Still need to do some research on which unit(s) to buy.


A windcharger with a charge regulator. Then it doesn't matter how much
power you use....

Larry writes:

"The wind always blows...."

It does??? Not around here. That is why the solar chargers are needed.

"Duffer" wrote in news:huUXh.18987$Uq.7208
@read2.cgocable.net:

It does??? Not around here. That is why the solar chargers are needed.




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


Larry
--

On 2007-04-24 15:58:26 -0400, Jerry Atkiin said:

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?

We do this with a solid 12w cell. I only connect one battery at a time
to it, as I don't really trust two identical batteries to be truly
identical, but plugging it into the cigarette lighter would allow you
to chose 1, 2 or both.

The small cells are fine without a regulator for the 100+ AH of group 31s.

--
Jere Lull
Tanzer 28 #4 out of Tolchester, MD
Xan's new pages: http://web.mac.com/jerelull/iWeb/Xan/
Our BVI pages: http://homepage.mac.com/jerelull/BVI/

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