Solar battery charger

solar battery charger and shunt regulator

I am want to trickle charge a single cell Lithum Polymer battery ( 3.7 ) volts from a solar cell ( as small as possible). I am looking for schematics or at least info on how to do this.
I am not talking solar panel type voltage sources but rather like
what you get on calculators.
Any help is hugely appriciated.


JJ

solar battery charger a small note

You could have enough solar cells to have a higher voltage than the battery and use the short circuit current as the current limiting. You will need a very low reverse leakage diode in series to keep the battery from discharging through the very large reverse leakage of solar cells during hours of darkness.

If you need to cut down the charging current you could block off a portion of all of the solar cells from the light.

solar battery charger ic

I also suggest a shunt voltage regulator after the solar cells. A shunt regulator will have less losses that a series regulator and will help in setting the charge max voltage.

Sonic

atmel solar charger

If you are going to make the charger MCU controlled, this application note might be usefull: Atmel AVR450: Battery Charger for SLA, NiCd, NiMH and Li-ion Batteries. You can also find some general info about charging.
App. note link: www.atmel.com/dyn/resources/prod_documents/doc1659.pdf
Source code in C and asm: www.atmel.com/dyn/resources/prod_documents/AVR450.zip
All the AVR app. notes: www.atmel.com/dyn/products/app_notes.asp?family_id=607
Lithum Polymer battery is pratically the same as Li-ion and they should be charged the same way.

solar shunt regulator

The battery charge processing is complex that u'd better choose a charge IC to do this job, or your battery should ephemeral.

charger solar atmel

Still the solar method of power generation is not effective toward its cost , isn't it?

battery charger ic solar cell

hayder9,
The reason for wanting to use solar charging is to have the convenience of not having to charge the battery conventionally as the usage of the device is very infrequent.


JJ

solar batery charge regulator ic

hey JJ..

Trickle charge will not be too demanding, but those calculator cells are small - 1.7v I think.. Try to get a few, connect in series and test output voltage in bright and dim light.

Those battery management IC's are pretty complex, sensing the optimal charge rate and battery lifetime for quickest charge. A waste for your application I think. Yes, an adjustable regulator and diode are probably a good idea.

Start with the cells (3x-4x in series =>3.5-6v) and add a big (10uf, 20uf) cap across the terminals.

Next add the LDO adusted to 3.7-3.8, and last, a small diode between the LDO and the + terminal of the battery. All grounds connected. This has added feature of running the radio (or whatever it is) off of sunlight if it is used during daytime!

solar battary charge rate

I am trying to figure out how to do something similar to this, so any help or directions you can point me in would be very helpful.

Here is what I am doing:

I have some shelves that have 1 or 2 white LED's in them that are currently powered from a single 9v battery in each shelf. The batteries do not last as long as I had hoped they would.

So I starting thinking that if I could use a rechargeable battery and trickle charge the battery from some small solar panels simliar to those in a calculator when they are not on (most of the day) to keep the battery charged up and then run the LED's off the battery.

I would like something small and unobtrusive hence the calculator like solar cells. Also, I would want it to all be part of the same circuit, and being the newbie that I am, do not fully understand (yet) how to combine the trickle charger and battery and LED within the same circuit, let alone design the trickle charger itself.

I am not looking for someone to design it for me, but if you can provide me with any information to get me on my way, I would appreciate it. Or even if it is possible.

Thanks!!

avr450.zip

Does anyone have any insight into this? Is it even possible? Thanks!