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# solar cell, 9v battery, indicator circuit

#1
12-12-12, 01:52 PM
Member
Join Date: Dec 2012
Location: United States
Posts: 13
solar cell, 9v battery, indicator circuit

I am looking for a little advice on some circuit work. I want to have a 9v battery powering some LED lights. I already have the schematic for that circuit. I also want this battery attached to a battery level indicator circuit. It will be a rechargeable 9v battery, and I want to use a solar cell to recharge it. So it would be solar cell to 9v battery to indicator circuit and also 9v to LED circuit. If I was too vague just let me know.

#2
12-12-12, 07:02 PM
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Join Date: Oct 2012
Location: Northern NJ - USA
Posts: 46,213
First thing......just so you are aware.
A regular 9 volt battery is made up of six 1.5 volt cells. 6 x 1.5 = 9v
A chargeable 9 volt battery is made up of seven 1.2 volt cells. 7 x 1.2 = 8.4v

So first your circuit needs to be based on a battery voltage of 8.4 volts.
Second....a battery charge meter would take up valuable storage capacity.
Third....with LED's run on a battery of this type you will have a short lamp duration.

You don't mention your application but I would lean towards a small sealed lead acid type battery. If you went with a 6 or 12 volt one you would have plenty of storage and the solar cell could just loaf along.

On edit: It appears that there may be NiMh 9 volt chargables that have higher voltage.

#3
12-13-12, 08:55 AM
Member
Join Date: Dec 2012
Location: United States
Posts: 13
I am building a DVD case with sliding doors. I will have 18 5mm LEDs that turn on only when the sliding door is open, so they may only be on for 20 seconds at a time a few times a week. The battery indicator isnt completely necessary, but I know even rechargeable batteries die at some point. I figured if I install a blinking LED somewhere in the circuit it would be nice. And as you may have guess, I just want the solar cell to keep recharging the battery. I figured it would work the same way as a calculator.

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