Lithium Ion Batteries for lights

[cool_hardware52]

I don't think a flood would discharge current as fast as a direct short with a nail.
I'm using this battery:
ICR-18650.H
3 sets of 5 wrapped around a dowel.
The batteries are from laptops, I am using the circuit in the laptop battery, and charging it with a laptop.
I'll be on vacation for a while so I won't work on it for another couple weeks.

Burner,

I'm assuming that your using a 5 x 3 setup, by that I mean 5 cells in parallel and three sets in series for a pack voltage of ~10.8 volts.

Was the original laptop battery also 10.8 volts nominal?

Did you interconnect all the cells of each Parallel group?

Some laptops use a very sophisticated charger that uses multiple means of charge control with more than one parameter for cut off. This redundancy is to assure no over charges.

For example the battery may be charged to a specfic voltage, but temperature is also tracked. Very often there is a maximum charge time also.

In other words the charger primarily looks at voltage, but if the pack over temps it stops charging, or if some time limit is reached it stops charging.

If your new pack has more total cells than the laptop battery it's based on, the charger may be "timing out" before your greater number of cells is charged.

I'd suggest a test that measures charge current and time. If you know the current and time you can tell if your getting anything like a full charge.

Say you have a 10.8 volt battery at 10 amphour. You have a 108 watthour battery. If the charger is delivering say 5 amps for 10 hours then is timing out you have delivered only 50 watthours of charge. (These examples are approximate as batteries don't charge with 100% efficency, but you get the point)

Your charger may even state what the nominal output is in terms of current. This helps if you cant easily measure the charge current.


Good luck,


Tobin George

 

[Burner]

You are correct in the setup. The batteries were originally 2x3, and i made it 5x3. It should be 11.1, 12ah. It could be timing out. The cells are interconnected properly, and a wire goes from each set to the board, for the circuit to tell if one set is getting charged more or less then the others. The other thing I wasn't sure of a good way to figure out was if the voltage is too low and the light is dropping out.
Current is easy to measure, especially if it stays pretty constant. Time is a little trickier because it lasts too long.
The charger is the laptop, so it doesn't really say what it will do. I think the battery pcb talks to the laptop over some bus and controls the charging.
I have a couple experiments to try to see if I can get more our of them.
Thanks for the suggestions.
Shane

 

[jtivat]

Hi, for anyone interested in using Li Ions check out this sight.
http://www.jsburlys.com/

These batteries have been used in high power lights for some time now and also have a very flat discharge rate.

You can also search for Pila at this site and see how they are being used in many different lights.
http://www.candlepowerforums.com/