[Milsurplus] solar panels

[Peter Gottlieb]

  Solar panels have a "maximum power point" which varies with, among 
other things, how bright the sun it.  The batteries have their own 
independent voltage and current limits.  That is the real reason for the 
solar charge controller - it manages both to maximize the efficiency of 
the PV array and the life of the battery.  Most large ones and some of 
the better smaller ones are buck-boost DC-DC converters.  I disagree 
that you can't afford a large enough battery array, it is simply a 
matter of sizing between PV array and battery system.  I've seen plenty 
of systems where the battery is way oversized compared to the array.

I normally don't deal much with small systems so don't have any specific 
recommendations for such, sorry.  I've built my own charge controllers 
for green radio projects but that was more because I could rather than 
that it made any sense to do so, with so many out there for cheap.

Peter



On 10/3/2010 8:20 AM, Gene Smar wrote:
> Tony:
>
>       Whatever solar panel you decide on, don't forget to buy a charge
> controller to go with it.  Solar panel DC output is very erratic, depending
> on sunshine (a.k.a insolation) and the output voltage can climb to somewhere
> around 140-150% of nominal batt terminal voltage.  E.g., a "12 VDC" solar
> panel could actually produce as much as 17 or so volts in bright sunshine.
> You'll need to have the controller between the panels and batts to maintain
> the proper charging voltage being fed to your batts.
>
>       The controller will also shunt any excess energy when your batts are
> fully charged (their terminal voltage is at 28-29 VDC) so you don't
> overcharge the batts.  (That's one problem with solar energy - you can't
> afford a large enough battery plant to hold all the energy that can be
> produced on a really sunny day.  This excess energy only raises the batt
> voltage, possibly damaging the cells.)
>
> 73 de
> Gene Smar  AD3F
>
>
>
> ----- Original Message -----
> From: "Tony Snider"<trsnider at cox.net>
> To:<armyradios at yahoogroups.com>
> Cc:<milsurplus at mailman.qth.net>
> Sent: Sunday, October 03, 2010 1:23 AM
> Subject: [Milsurplus] solar panels
>
>
>> Hello,
>> I have a S-280 comm shelter I have mounted green radios in and I want use
>> a solar charger, does anyone have any panels for sale or a good source?? I
>> am looking for 24VDC to charge lead acid batteries?
>> new to solar systems so any help appreciated on battery types, regulators,
>> and panels
>>
>> THANKS MUCH
>> Tony
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