I'm back with a small project!

[zachtheterrible]

Hi everyone, for those of you who remember me, it's been a while. I got into fourwheelin and have been having so much fun with it electronics sorta got put on the backburner! There's a picture of my 84 Toyota 4x4, it's got a solid axle with 4.88 gears and Aussie autolockers front n rear, which lets it go anywhere, I've installed an MSD ignition, weber carb, flowmaster exhaust, just to name a few, and in the next couple of weeks am going to fabricate an exocage for it, and after that do a 3-link suspension with coilovers up front.

Anywho, I made an LED flashlight a long time ago with a lumiled 3W LED, and have since decided it's not bright enough, so I"m going to use lumileds new K2 LED, which can soak up 1A of current! I plan to use li-ion rechargable cells to power it which is great because coincidentally the normal driving voltage of the LED Is about 3.7volts, exactly what the li-ion cell puts out.

My question is about charging/discharging the cells in parallel, so I can have a 3.7V 30 or 40Ah battery. There are premade PCBs which limit the charging/discharging to protect the batteries. Can I use one PCB to charge all of the batteries in parallel at once? Cuz that'd be great.

One other question is, how is the discharge curve on Li-ion cells?

 

[justDIY]

the discharge curve is mostly flat ... you start at 4.2v and end at 2.9 to 3.0v, most of the life is at 3.6-3.7v

large strictly parallel arrays are discouraged, unless you have some method to monitor / charge each cell separately. really, the same thing applies for series arrays too, you need to monitor each cell separately, but can charge them as a whole

that being said, I have two 2.6ah cells in parallel, each cell has its own protection circuit. They charge and discharge together. I'm still here and haven't lost any eyebrows.