Need advice on solar panel setup for Propeller

Oldbitcollector (Jeff)

Ok, Beans solar cells have been on my workshop shelf for a year...
It's time to get them together and create a 3x3 cell for my Propeller.

I need some advice from the pros...

I'm thinking that I might be able to purchase some rechargeable AA's
for my 5 AA battery pack I got off Bean at UPENE this year.
I'd like to charge them with the set of cells.

Is there any reason I should need more than some simple diodes
to keep the batteries discharging into the cells? Or do I need
to create some sort of charging circuit?

Thanks in advance,
OBC

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Manetheren

A charging circuit would be the best depending on the type of batteries that you have gotten. Some batteries require that they are discharged and then charged and some are ok to keep fully charged. A regulator with diodes might be fine for it depending on the type of batteries. Look at the data sheet on the type of batteries you get.

Another thing to keep in mind is that the voltage out of the chargers is more than the voltage of the batteries.

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Tia'Shar Manetheren


Post Edited (Manetheren) : 8/29/2009 9:14:46 PM GMT

Manetheren

I have a whole set of them and would like to do the same thing.

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Tia'Shar Manetheren

CounterRotatingProps

OBC,

as M. says, you have to charge them a specific way depending on what kind they are (NiCd, NiMH, LiIon) - each one's different... and since we're on this subject...

does anyone have or know of a generic battery circuit that allows you to manually switch between types?

- H

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Beau Schwabe

OBC,

Are these the same cells that Bean had at the Expo? 4V 40mA?

If so, then the "charge them a specific way depending on what kind they are (NiCd, NiMH, LiIon) - each one's different" may not apply since you don't meet the initial current requirements for the charge. Instead about all that you can do is setup a trickle charge. With 40mA, a direct connection IS a trickle charge, which is what those cells are designed to do.

Find the lowest forward voltage diode you can find near 0.3V ... you can also use a MOSFET transistor with the drain tied to the gate to "function" like a diode.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

CounterRotatingProps

Beau,

Li-ion batts are still new territory for me - if we can just trickle them, do we have to detect when they're full and then shut off the charger?

thanks
- H

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Beau Schwabe

CounterRotatingProps,

"if we can just trickle them, do we have to detect when they're full and then shut off the charger?"

I'm not sure about over charge on the Li-ion ... I've always kept it safe and monitored the voltage.· I have succesfully recharged 3.7V Li-ion batteries with nothing more than a 5V supply, a Si series Diode, and a 100 Ohm resistor... the "cut-off"/trickle voltage is about 4.25V and in this arrangement, the diode and resistor prevents any charging above that threshold.

The disadvantage of this circuit is that if the power goes out, the battery will discharge ... perhaps a variation on this theme will solve that problem.




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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

CounterRotatingProps

Thanks Beau - that's much more simple than I'd guessed. -H

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