rechargeable battery help

[iFred]

I have a project in mind for some of the broken solar cells that I have. My application is basically a night light using the new high and ultra high brightness LED's.  These LED's are in the  4000-10,000 mcd range at about 20ma or so. That's equivalent to 4-10 candle power I believe.

I want to hook the broken solar cells together to a rechargeable battery near my windows so it gets charged during the day, LED stays on all the time, day & night... The only problem I am having is picking out the right type of cheap rechargeable batteries for the project. Even a small battery in the 450-850ma range would be ideal. Also I want the most batteries I can get at the cheapest price (obviously). So I am going to buy bulk. They should last a long time in years.

I did some searches on Ebay and came up with some interesting batteries, but do not know what would be best for this type of application. There are so many to choose from. I think that maybe the lithium or lithium ion batteries may work. What do you think?

http://search.ebay.com/lithium_Wholesale-Lots_W0QQsofocusZbsQQsbrftogZ1QQcatrefZC6QQsojsZ1QQfromZR10



QQsacategoryZ61494Q26catrefQ3DC6QQsotrZ2QQsosortpropertyZ1Q26sosortorderQ3D1QQcoactionZcompareQQcopa



genumZ1QQcoentrypageZsearch

Thanks in advance for the help!

[iFred]

Also found this one in which has different types of cells. Ohhh the confusion...

http://stores.ebay.com/ONLYBATTERIES-COM_W0QQsspagenameZl2QQtZkm

[iFred]

Poly carbonmonofluoride lithium batteries

Manganese dioxide lithium batteries

Vanadium pentoxide lithium batteries

Manganese titanium lithium rechargeable

Manganese lithium rechargeable batteries

Alkaline batteries

Zinc air batteries

Zinc-Carbon batteries

Zinc-Manganese-Dioxide Alkaline Cells

Rechargeable Alkaline Batteries

Nickel-Cadmium (Ni-Cd) (nicad)

Nickel-Metal Hydride (Ni-MH)

Nickel-Zinc (Ni-Z)

Lithium and Lithium Ion

[JeroenH]

For longevity I would use wet lead-acid cells. Are you intentionally running the LEDs 24/7? Because it would save you PV-surface and battery capacity if you'd devise a simple circuit which shuts off the LEDs during daytime. It may not matter in the summer (lots of sunshine) but you'll notice it in the winter.

I have a charge controller which can switch the load on and off depending on the absence of presence of ligt (it uses the PV panel as a sensor).

http://www.stecasolar.com/pdf/PR2000_E.pdf

That might be useful in your situation.

[iFred]

Product Description LED's

    * Emitted Colour : WHITE

    * Size (mm) : 5mm T1 3/4

    * Lens Colour : Water Clear

    * Peak Wave Length (nm) : N/A

    * Forward Voltage (V) : 3.2 ~ 3.8

    * Reverse Current (uA) : <=30

    * Luminous Intensity Typ Iv (mcd) : Average in 8000

    * Life Rating : 100,000 Hours

    * Viewing Angle : 20 ~ 25 Degree

Absolute Maximum Ratings (Ta=25°C)

    * Max Power Dissipation : 80mw

    * Max Continuous Forward Current : 30mA

    * Max Peak Forward Current : 75mA

    * Reverse Voltage : 5~6V

    * Lead Soldering Temperature : 240°C (<5Sec)

    * Operating Temperature Range : -25°C ~ +85°C

    * Preservative Temperature Range : -30°C ~ +100°C

[iFred]

Actually, I could build a simple transistor circuit which would check for the absence of light or current from the panel, if so, turn on light. Not a major problem but thanks for mentioning it. Thanks for the PDF info too!!

[juiced]

Dont just go around using Li-Ion batteries. They NEED very specific controlled charges that cannot flux. If they are even slightly deranged, i guess they go BOOM!

  Im looking for a pic of the aftermath of BOOM. I think its somewhere in these two threads.

 (Battery reviving advice)

http://www.juiced.ca/phpbb/viewtopic.php?t=698

  (Vehicule Battery Info)

http://www.juiced.ca/phpbb/viewtopic.php?t=711

   Im personally hoping to come across a bunch of matching NMH packs. They seem to last the most and beating them up is actually a good, recommended thing.

 Quote: "The long and short of it is this....if your Li-Ion battery no longer works, forget it....it CANNOT be recovered. If you don't believe me, I'll email you the photographs of a colleague who DID try a bench charger on one of these packs. He will have the scars for life....no kidding! An incorrectly charged Li-Ion cell is like a stick of dynamite."

[ghurd]

I would use 8 AA Ni-mh, 2000ma-h -ish. About $2 each.

If the capacity is enough for the number of LEDs you want to use.

12v is the majic number for white LEDs.

I made a light sensor LED light. 3 parts. Too simple.

CDS cell controlled mosfet.

Battery + to mosfet in, out to LEDs and resistors.

Battery + to hi ohm resistor, resistor to gate and CDS cell. CDS cell to ground.

May have to switch the resistor and CDS, depending on the CDS type.

The loss in the mosfet would have been in a current limiting resistor anyway.

The loss in the resistor and CDS cell would be a microamp or so? Not much though.

The resistor value can be changed for sensitivity.

IRF510 (it is overkill, but was on the bench), 50 cents, 1" CDS, .25 and a 2 cent resistor.  77 cents surplus.

The LEDs would fade to bright as the sun went down. Kind of neat for so simple.

G-

[troy]

A small wet lead acid cell, where you can both check the electrolyte and add distilled water would be my first choice.  Cheap, available, reliable and good life if they get even minimal maint.  That's assuming you're keeping them charged nicely.  Overcharging a bit is ok too, so long as you watch the electrolyte levels.  I'm thinking very small lawn mower or motorcycle battery.  Should be less than $15.

Best regards,

troy

[nothing to lose]

Just curious but what would be the losses if using a junk 12v battery for such low power items?

I mean I have some I have not tried to bring back to life yet, but they put out a reasonable 8V or such as is straight from the scrap yard.

So lets say you pump in 10V to a battery that only charges to 8V then run maybe 7.5V of LEDS off that 8V battery.

I don't know why, I guess one cell might be badly shorted, but I have a 9V (was 12V) battery that will heat my load tester. As a 12v it's junk currantly as it takes a charge and holds at only 9V. Since it does heat a 50amp load tester I would think it should be fine to run say 6-9V of lights for the yard or maybe some 12V computer fans at a lower speed. Just low powered stuff that works at variable voltages.

Since I think my LEDS are 1.5V-2V I can wire them to anything up to 6 for 9V very easy. Somthing I plan to do at least once, but I expect LEDS to take forever to kill the battery even without charging it any. Normal car sized battery, but a deep cycle.

I am sure there is a good reason that's not a good idea, but I haven't tried it yet, just something I was thinking about, and since a 12V battery only holding 9V should be easy to find and free (or scrap value) thought if it's worth a try might work for your solar pannels and LEDS project.

[richhagen]

A couple of years back or so, I had one of those solar led yard lights.  It wasn't working, so I checked it out and found that the batteries were no good.  I replaced the batteries with 22 farads of memory capacitors.  I had a couple of 5.1 volt zeners as s shunt regulator to prevent over charging.  The 12 solar cell 'chips' were wired in series and connected through a diode to the capacitor bank.  I didn't like the two bi-polar transistor circuit they had in the thing, so I built a little comparator circuit with a low power op amp and the existing cadmium sulfide sensor to turn the led on.  The circuit kicks on in the evening very brightly, and then slowly fades to dim over the next 4 hours.  It remains dimly lit all the way until dawn.  I don't have it any more, but it still works in the yard where it sits as I stop by there every so often.  The batteries in the rest of the similar units gave out a long time ago.  I think the weak point is the energy storage.  If I had built it with about 50 farads (two 100 farad 2.5v capacitors would probably work)at 5.1 volts or greater, it would probably stay pretty bright all night. Just having fun  Rich Hagen

[juiced]

Dont the batteries have ill effects from use below the specified levels? Boiling, H2..  might be off on this.