48v Solar panel

[pfcgreene]

Can 48vdc-40w  solar panels be used for a 12v system. Can I run these through a dc-dc converter/regulator-48dc input /14dc output. Would the watt and amp values change.

[Opera House]

You can either go directly into the battery with the solar panel with the same current or through a switcher and multiply the current for the same wattage minus about 10%.  This loss can be more than made up by operating at the maximum power point which is much higher than nominal 48V.  Converter selection is a little more complicated because you are at a kind of in between voltage for common applications (above 35 and below 90). The panels act more like a constant current source. You will notice that normal current and short circuit current are about the same.  So, you can feed it directly into a battery with a great losss in effective wattage as long as you protect against overcharging.  

[DanB]

I think an MPPT controller would allow for that and things might be quite efficient.  They're not cheap though...

[Volvo farmer]

Doesn't that new nifty MPPT charge controller from Outback do that? I think I read you can feed it up to 120VDC and it will charge into 12, 24 or 48V batteries. The thing ain't cheap ($600) but for a large array, I'd bet you can save a hundred bucks or more in copper wire by running a higher array voltage.

Volvo Farmer

[DanB]

yes, and there are cheaper ones by other manufacturers if you have a small array.

[ghurd]

Do you have a lot of these panels?

If there is only a couple, it may be cheaper and easier to buy 12v panels instead of everything else.

G-

[Opera House]

If you look back quite a few posts, there was a link to an Austrailian poster that used a simple switcher chip (an old one that I nave never found) and he regulated on the input side to the common optimum voltage. This circuit has neither a common positive or negative. Just turned the pot to get the maximum output current.  You charge an input cap that acts like a battery so the regulator actually operates in bursts. Since you are less than an amp on the input side, you could easily use any 200V FET and get away with using the primary of a 500 watt 120V transformer (in order to get the resistance down).  Running the switcher at 100HZ would let you use regular diodes with higher voltage than low voltage switchers.  The common TL494 would do this as long as you protected its power to about 20V, the max gate of many FETs.  Do a web search on the application notes and see if you can understand it.

[erne]

go buy a trace c-40 and set it to 12 volts. It will handle up to 60 volts @ 45 amps and convert it down for you. cost $100.If you have questions about it call their tec line.---erne

[drdongle]

I looked for that post, where is it?

Carpe Vigor

Dr.D

[Opera House]

The schematic was at  http://www.acs.comcen.com.au/projects1.html  but this seems to have dissappered.  

[Nando]

YES you can use a converter a 32 (28 to 56 volts) to 14 Volts.

Also, there are inexpensive converters that can be set to a float charge level and charge the battery, at this moment I do not remember the two catalogs that you could use to do that.

Regards

Nando