Solar powered Kindle Touch

[nick-tech]

I still recommend this 100% I didn't have to charge my kindle ever since then, the battery isn't having any problems.

zxczxc:
since the circuit is attached directly to the battery, the kindle mainboard doesnt "see" it at all. You can charge it via AC as usual. The charging current will be the sum of the mainboards current and the one from the solar regulator. If you attach a very large solar cell, it could cause your battery to overheat, but the mainboard would recognize that and reduce the current. The solar circuit will always charge according to its built in charging curve, of course limited by the amout of power provided by the cell.

idoit:
I don't know why you want to have the ability to disable the charging circuit. It will never overcharge, the IC will take care of it. But if you want to disable it you can always install a switch in one of the lines going to the battery or the cell. As far as I remember the IC has an enable/disable port that has to be left floating or pulled to gnd in order to enable/disable. You could try to attach that port to the charging indicator led, to disable charging while the LED is lid. (don't remember which way it works..)

You also could disable charging by software: The battery management chip measures the current drawn from the battery, to disable charging write a script that uses (CPU) power to consume as much energy as the solar cell provides.. Under heavy load the kindle can consume about 300 mA (indexing, frequent screen updates, Wifi), thats more than any solar cell that fits in the backcover can provide.


One last tip: By now there is another IC from ST called SPV1040, that does pretty much the same thing, but also comes with mpp tracking. I would love to try one of these out, but they don't want to send me an engeneering sample.

Maybe one of you guys is lucky!
Have fun!

[knc1]

The tech. stuff:

[thatworkshop]

@nick-tech: I don't think sampling exists for this, eh?

So what you are saying about SPV1040 is that essentially MPP is what makers like SolarFocus use for their solar battery cases?

[knc1]

So just spend $4 you cheap skates:
http://www.mouser.com/ProductDetail/...L54EXT6pRPOpLU
or perhaps:
http://www.mouser.com/ProductDetail/...EF%2fl9Oa9cyhP

[thatworkshop]

Originally Posted by knc1

So just spend $4 you cheap skates:
http://www.mouser.com/ProductDetail/...L54EXT6pRPOpLU
or perhaps:
http://www.mouser.com/ProductDetail/...EF%2fl9Oa9cyhP

nick-tech, knc1: To make it worth the shipment to Canada, I'd like to do combined shipment.
There is a done project to enable bluetooth for DXG (search), so I want solar + bluetooth + maybe WiFi module???!!! Do you have any suggestion?

I think someone already said forget about WiFi on this thing, but still I'd like to try.

[knc1]

mouser has Canada site/warehousing.
I picked them because they will ship small quantities.
Even though the standard unit is a reel of 4,000 pieces - they will cut one off for you.
(and I suppose somebody gets a reel with 3,999 pieces.)

[blkhawk]

wow - integrated mppt. Thats really something i gotta try. Too bad mouser wants 20EUR for package and handling - thats just too much.

[nick-tech]

Thats also my problem. I don't want to pay 20 € for shipping as long as my solution works..

But if (someday) my kindle touch will be replaced by something with a lit screen, I will design a new board...

[knc1]

Originally Posted by nick-tech

Thats also my problem. I don't want to pay 20 € for shipping as long as my solution works..

But if (someday) my kindle touch will be replaced by something with a lit screen, I will design a new board...

Right!

Turn the screen lights all the way up -
Face the solar panel towards the screen -
**Self Powered Forever** Yeah!!!

= = = =

Seriously -
There are also chips available that manage Li-Ion charge from multiple sources (like solar + dc charger).
I have no numbers or links - just the general knowledge (try Maxium - I get their news letter and that is probably where I read about it).