Solar Chrgr

[ILO]

hello I am in need of some help I am building 3 outdoor item's and need to
be able to charge each unit 1st 2AA, 2nd 4AA and Last 8AA batteries at
1500-2000mah each. I have been searching the net for diagrams or kits to
build or from scratch. I am not sure how to figure the solar output and
voltage to accomplish what I need. I am putting a photocell in line to
turn on at night off during day on each device. I am limited in size of
solar cell cell cannot be any wider than 1" wide but length can be from
3"-18" long abd .2-.4 thick. I know I need a Diode to stop from
discharging at night, but not sure how to keep from burning up or melting
battery by over charging the batteries and what the photocell rating needs
to be (PHOTOCELL, 90mW, 150V PEAK,
27KohmMAX LIGHT, 2MohmMIN DARK
Jameco #: 120310 ) there are so many to pick from and I'm at a loss,
please help I am needing big time help I keep getting further confused the
more I look on the web. If you can help with any part I would be
greatfull. Thank You. ILO

[dyarker]

Do you mean 2xAA in series for about 3V, 4xAA in series for about 6V, and 8xAA in series for about 12V? Or, the AAs in parallel for different current capacities at about 1.5V?<p>Where did you get 1500mAH - 2000mAH figure? That is VERY high for normal NiCd AAs!<p>I don't think 18 sq inches of solar cells will come close to that amount of current. Which ones did you have in mind?<p>What are the loads you are powering?<p>With more details, and maybe a proposed schematic diagram, I'm sure you'll lots of help here.<p>Cheers,

[Engineer1138]

Hi ILO. I'm doing a charger project right now so I'd be glad to help. I'm using the Maxim Max712 charger IC. Charging is pretty straightforward at lower currents, but I'm trying to charge a 3000mAH battery at a 2C rate, so I am having some trouble.<p>If you want to ask specific questions, just post here or send me a private message.<p> ************
I was reading the PICing it... thread and it's kind of amusing. The first battery chargers I designed used microcontrollers with A/D converters to monitor the battery voltage and look for the "knee" that told when to shutoff. It's much easier with a charger chip, but the chip costs more than a small uC, so there is that tradeoff.<p>Oh, and as far as controlling an LCD without uC, well the guy I designed the charge controllers for was an "old school" engineer who showed me the schematic for a part of a medical instrument he designed in the early 70's. Pages of logic schematics for something that could be done in a single AVR. I sure don't long for those days!

[dyarker]

(here is a better place to ask your questions than e-mail, 'cause I can answer from home or work, and if I forget something somebody else will catch it)<p>What are the loads you are powering?