Up-Converting Voltage from .56 Volts to 12.6 Volts

[schoonerdog]

I have a low wattage application which runs on 12 volts. I can buy individual cells pretty cheaply which are 4 watts putting out .56 volts. Does anyone know of a source where I can buy a small, cheap converter to convert this voltage from .56 volts to 12.6 volts?

[schoonerdog]

If there's nothing out there as a small electronic part, any kits, or DIY solutions?

[ViribusUnitis]

Stick 22 of them in series, and you should be good to go.

It should actuly deliver 12.3 volts, but that should be close enough, cause as soon as you put a little load, they'll probably drop down closer to 12 volts.

[schoonerdog]

Yes, but the result would be 22 x 4 watts, or 88 watt panel. Way to large for my application, hence the need to try to simply upconvert the voltage of the single 4 watt cell.

[Paul L]

You can find DC-to-DC converters that will do 3.3 v to 12v in places online like
DC/DC-Converter Power Flex Search - RECOM

Paul L

[s/v Jedi]

Originally Posted by schoonerdog

Yes, but the result would be 22 x 4 watts, or 88 watt panel. Way to large for my application, hence the need to try to simply upconvert the voltage of the single 4 watt cell.

you mean solar cells? get a miniature 12V panel instead, available from 1W up, like here: Kyocera 1.2W 12V Mini Solar Panel - 1 to 50 Watt Solar Panels @ AltE

cheers,
Nick.

[LiFeTech Energy]

As Paul L has suggested you can connect 6 cells in series and then use a 3.3V - 12V DC/DC converter (which are quite common).

[schoonerdog]

I've been looking at some smaller wattage 12v panels. The issue is mainly cost. A single 4 watt solar cell you can buy for around $5. A 4 watt 12v panel of similar power would cost around $75. I do see things out there that look like they are 12v chargers with two siemens monocrystalline cells put together (probably in series) and charge at 12v like this Amazon.com: 4 Watt 250 MA 12V Mono-crystalline zipper bag Solar Battery Charger Kit with Siemens Solar Cells: Electronics. If each cell is .5 volts than they up converting the 1v output to 12.6 volts somehow. So it can be done I guess. Maybe I should buy one, tear it apart and see what they are using....

[btrayfors]

You can buy a new 4.5 watt solar panel for $44:
COLEMAN NEW 300MA 4.5 WATT SOLAR PANEL CL-300 - eBay (item 170456575518 end time Apr-07-10 18:39:46 PDT)

How much is your time worth to screw around with building one? :-)

B.

[senormechanico]

How about 2 of these?
6V 100mA 0.6W small solar panel with a diode inside - eBay (item 390175990094 end time Apr-04-10 10:24:52 PDT)

[schoonerdog]

Thanks for that link. I see they also sell this:
17.5V 290MA 5W solar panels solar power panels 5watt - eBay (item 220410887009 end time Apr-03-10 00:53:20 PDT)

That goes for $5 watt or $25 which is really in the ball park, especially since they seem to be well made.

Now a question, if the device I'm charging just has a 2.1 amp hour battery, would a 5 watt panel need to be regulated?

Originally Posted by senormechanico

How about 2 of these?
6V 100mA 0.6W small solar panel with a diode inside - eBay (item 390175990094 end time Apr-04-10 10:24:52 PDT)

[ctsbillc]

You are best not over-voltaging the battery, dependant on the battery type, it will have a voltage which it's best not to exceed (small gel cells are usually 2.35 Volt/cell, for example), and that should be what your power supply is set to.

Bill

[seandepagnier]

putting cells in series reduces shade tolerance of the panel, however it is probably really inefficient to convert .5 volts up to 12. If you had at least 3 volts to work with the efficiency would probably be more like 80% with a DC/DC boost converter. The other advantage is you could set the DC/DC converter to 14.4v so it would never overcharge the battery.

[senormechanico]

I really doubt you will find any electronics which will work on 0.56 volts in the first place.
The forward biased conduction point of a silicon junction is around 0.7 volts.

[ctsbillc]

Ah, don't think bopolar. Don't necessarily think Silicon either (Germanium is 0.2V)

Here's a ultra low voltage charge pump Overview - Ultra-Low Voltage Operation Charge Pump IC for Step-up DC-DC Converter Startup S-882Z series

Still true that it's not the way to go though, put the cells in series, and make sure none of them are shaded.

Bill