Solar charging

Hi all,

I want to charge four re-chargeable AA cells with a solar cell array (quick charge

Reply to
Steve Newport
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Most important issue is what KIND of AA batteries? Each chemistry has a different method for charging quickly. TTYL

Reply to
repatch

True, thats another problem.

I want a cell produc>Most important issue is what KIND of AA batteries? Each chemistry has a

Reply to
Steve Newport

NiMh AA can be obtained in capacities approaching 2500mAh. Can I suggest you look at buying one of those fast DeltaV four cell chargers, which is able to work via both a wall wart or alternatively from a car

12v supply. These charge my 2200mAh to perfection in about 90minutes, lower capacity cell sets take less.

To this you can then simply add a suitably rated solar panel with a 12v output, running the charger directly from this.

Reply to
Harry Bloomfield

"Harry Bloomfield" wrote in message news: snipped-for-privacy@tiscali.co.uk...

The size you mention is typically NiCd but Metal Hydride is also available with almost identical charging and voltage characteristics but better capacity. The faster you charge either of them the less efficient the charge and the greater the wear on the cells. There are several battery charge controllers that can orchestrate the charge process but assuming a series connection, you will need >1.2 amps at about 7 volts. Solar panels typically come in 6 volt or 12 volt assemblies so some form of regulator will be needed. Syncronous switching is the most efficient but a little more difficult to work with than switching with diode rectification. Linear switching is the least efficient and will require a panel with at least 8 volts of output. Solar panels have a variable and high equivelent source resistance so they complicate the design of regulators. The charge rate you are wanting makes for a panel of about 15 watts. Such a fast charge rate also favors a controlled temperature. If you can scale back to say a 200ma charge rate (about 8 hours), you can simplify by possibly eliminating both the regulator and the most of the charge control. Some form of temperature sense on the cells to stop or reduce the charge would extend battery life. These cell technologies turn excess energy into heat which itself slowly shortens cell life but the overcharge does not. Lithium cells are a higher voltage and require sophisticated charge control on a per cell basis to avoid cell destruction.

Reply to
Comcast Newsgroups

Your solar array will have to provide over 5 amps at something over the charging voltage if charging in parallel, or higher voltage at lower current (but > 1 amp) if charging in series. Either way, that translates to $$ and size. If you already have that kind of solar power available, fine, but I have the thought that you are doing this from scratch. Is that correct?

If you are doing this from scratch for the sole purpose of charging 4 AA batteries in 60 minutes, it may be a non-starter financially, even if you charge those batteries 300 times. AA's (Energizer) go for .35 each at

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So 300 would cost $105. A solar cell rated at 17V, 1000mA is $78.95 at
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, and you still have to buy (or build) the charger and batteries. There are a number of factors to add: You can't expect to get full power from the solar panel when conditions are not optimal; because the panel is limited to 1 amp you can't get 1200mAh charge in 1 hour; you'll probably charge the cells < 300 times; your panel will deteriorate over time; etc.

Reply to
ehsjr

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