[Rhodes22-list] Solar Panels

[Slim]

Dave,

Thanks a million for the basic overview.  That's just what I was looking
for.  With that explanation, now I can run my tests and at least do some
diagnosis.  

I do not have a generator on the outboard nor do I have electric start or a
stereo system.  The batts just run the lights, the VHF radio and the
cigarette lighter to charge the cell phones.

Slim

On 6/13/06 12:13 AM, "DCLewis1 at aol.com" <DCLewis1 at aol.com> wrote:

> 
> Slim, 
> 
> A little knowledge is a dangerous thing, and I¹m proof of that.   I¹m
> confident the guys on the board will have a good answer for you, but until
> they 
> respond let me take a wild crack at some of your questions.
> 
> If your boat is like mine, it¹s plumbed for 12 volts DC. You¹ve got 2  batts
> aboard. The main power switch adjacent to the V-berth lets you chose which
> battery to use to power your boat, or you can set the switch to BOTH and they
> will both power the boat together. If the batts were in series your electrical
> systems would be running of 12 volts when only 1 batt was being used, but 24
> volts when they both were being used - not likely.  Conclusion: when run
> together your batts are in parallel.
> 
> Your solar panels are supposed to trickle charge your batts. One may go  to
> one batt, the other to the other, so that when your main power switch is OFF
> each batt still gets a trickle. You can check this out on a sunny day.
> Disconnect the leads to your batts and using a voltmeter measure the voltage
> across 
> the loose disconnected leads, you should measure 12 volts, coming down  from
> the solar panels. Cover one panel, if the voltage goes away on one set of
> loose terminal leads, that¹s the panel that¹s supporting that batt, but also
> check the terminals from the other batt. If you cover one solar cell and both
> batts still show 12 volts (or if the voltage disappears on both sets of leads)
> they are wired in parallel from the solar panel¹s perspective. I haven¹t done
> this, but it should work.
> 
> Bigger (area) solar panels generally mean more power, or amps, but the
> output voltage is fixed. Generally, in my experience, they are sized for 12
> volts, 
> because they are usually used to trickle charge a lead acid auto batt.  But
> you should probably check, because the minute you don¹t you will find that
> what you¹ve bought is designed for some other voltage.
> 
> If the panel is designed to work with a lead acid auto batt, it¹s  output
> voltage is about 12 volts. The other 2 characteristics are power (watts)  and
> current (amps). This is DC (Direct Current), so Power = Volts x Amps, you¹ve
> set 
> the volts, if you set the power you¹ve automatically set the amps and vice
> versa.  So if you know the Watts you know the Amps and vice versa, if you
> know 
> the design working voltage (12V).
> 
> How big a panel is ³enough²?  Solar panels are generally  trickle chargers,
> not prime power sources. Your batts handle the big surges -  and they also
> carry all the load at night. If you¹ve got a generator on your OB,  you may
> not 
> even need the panels, unless you go a long time without running your  OB. If
> you don¹t have a generator, you may need the trickle charge the solar  panel
> provides. How big a trickle charge? You can assess your typical usage and  the
> size of batts and come up with an estimate, that should then be rounded up
> significantly, but for your purposes a good start might be the realization
> that  
> what you had worked, and the holes are pre-drilled, i.e. you might consider
> getting what you had because it worked.
> 
> If you want to ignore the pre-drilled aspect of your project and get a  new
> and different solar panel, you might measure the area of the panel and get a
> panel that is about that size. We all work with the same sun, the same silicon
> solar cells (approximately), and the systems are designed to work into 12
> volts  (be sure that's the case). Getting the same area solar panel should
> give 
> you  roughly the same current generating capacity as your old solar panel -
> within  bounds - unless the cells are markedly more or less efficient.
> 
> Or you might consider scaling down and not replacing the panel.  Particularly
> if you've got a generator on your OB, that might suffice to charge  your
> batts.  I assume (but don't know) that a lot of the people on the  board do
> very 
> well with 1 panel.  Your usage profile may not be much  different than theirs.
> 
> I don¹t know if this helps.
> 
> Dave
> 
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