# 18650 Ideas about build a DIY power bank to charge my cell phone?

#### Dr.killjoy

Joined Apr 28, 2013
1,196
Over the years I have collected a few 18650 cells and I am trying to find a use for them..I was thinking about build a DIY power bank to charge my cell phone but I am open for ideas here ..

Thanks
Jay

Joined Nov 5, 2010
215
Whatever you do with it, get a "protection circuit". I put a couple of them in my old NiCd-powered power screwdriver, and got an R/C (radio/control) balanced charger to charge them, but I didn't have a protection circuit. The second or third time I ran it down, the weaker cell stopped recharging. When you have a series battery pack and you run it down to near depletion, the weakest cell will be driven down to zero (and even negatively biased if you run it down far enough). That kills cells like these.

I went on Amazon and got myself a cute little 2-cell protection circuit PCB assembly. I just got my new cells and still have to wire it up.

So in general they're a good replacement for NiCd/NiMH in appliances or toys that had multiples of three cells. Three NiCd/NiMH = one LiIon in voltage. So tools that are 3.6V, 7.2V, 10.8V, 14.4V. You get an R/C multi-cell "balance" charging cable like this that will let you charge it with an inexpensive hobby charger and will keep your cells in balance.

Joined Nov 5, 2010
215
Just what I am trying to do here, but cant seem to get any output?

As near as I can tell, Dave, you have one bad (below cutoff threshold, usually 3.0V) cell and the protection circuit is cutting it out so it won't even charge. Best way to charge these is with hobby chargers that charge the cells individually (with a "balance" charge cable). But it necessarily bypasses the protection circuit for charging. Still, with multi-cell Li-Ion/LiPoly packs, it's the best way to charge.

#### Externet

Joined Nov 29, 2005
1,662
My electric broom had a series of three NiCd cells. Now has three 18650 in parallel.
My baby LED flaslights used 3 AAA cells in a holder, now a single 18650. Larger flashlights run on 18650 too.
My electric shaver got the transplant too. An intercom too.
Also my two 12V NiCd drills have now three 18650 in series.
My electric screwdriver had two NiCd, not anymore.
My spectrum analyzer had a 3.6V battery for memory backup, now a 18650.
And I may forget others...

#### AnasMalas

Joined Nov 27, 2015
66
if you are into latte making then you can mod the "Latte foamers" (although i personally use em for stirring, but thats just me) you can get one of the 3$ikea ones and mod it... semi related, i modded mine be sawing off most of the battery compartment, soldered on a usb connector at 90 degrees, and just inset the generic power banks to use it. runs great and is much more powerful (5v vs 3v)... you could also make some circuits such as LED lights all over you house, get special holders made just for the cells, and just light up some decoration! example if you have a small table in the middle of your living room, you could decorate that! just dont forget to use protection. if you dont, then expect to use them for some barbecue! although human meat isnt that appetizing is it Thread Starter #### Dr.killjoy Joined Apr 28, 2013 1,196 All very well, i have three 3.7V 9900mAh cells, but i cant charge the buggers with this protection pcb.... Wait what is the cell capacity per cell again?? #### Dodgydave Joined Jun 22, 2012 10,050 9900maH, i can charge them up on my atx psu no problem, but this poxy pcb won't work, i have ordered a different one. #### AnasMalas Joined Nov 27, 2015 66 9900maH, i can charge them up on my atx psu no problem, but this poxy pcb won't work, i have ordered a different one. IN 18650 SIZE!! oh my... who ever sold them slapped an extra zero at the end it seems man... this size cant hold more than 3200 if even that for the most expensive cell.... that is surely dodgy, dave! Thread Starter #### Dr.killjoy Joined Apr 28, 2013 1,196 IN 18650 SIZE!! oh my... who ever sold them slapped an extra zero at the end it seems man... this size cant hold more than 3200 if even that for the most expensive cell.... that is surely dodgy, dave! Hence my reply ..So pcb might be good and cells bad then.. #### Dodgydave Joined Jun 22, 2012 10,050 Yep 9900mah #### hp1729 Joined Nov 23, 2015 2,304 Over the years I have collected a few 18650 cells and I am trying to find a use for them..I was thinking about build a DIY power bank to charge my cell phone but I am open for ideas here .. Thanks Jay There is the larger 32650 for more mAh. Usually the charger output is 5 V. The charging chip inside the phone brings it down to the 3.7 V. So you need a circuit to bring the external battery up to 5 V. #### AnasMalas Joined Nov 27, 2015 66 Now, dodgydave, please now that its working, get a 15 ohm 0.5 watt resistor, put a voltmeter and an ammeter on, put a watch, film the whole thing in 1FPS time laps, and show us that your batteries will put out 0.25 Amps (I=V/R = 3.6/15 = 0.24A) for 9.9/0.25 = 39.6 hours or if it will be just be 3.96 hours... i really want to know because these are so energy dense they could help create a flux capacitor!! #### AnasMalas Joined Nov 27, 2015 66 Interesting! 9900 mAh at what current level I wonder. You wouldn't have a data sheet for the battery would you? I really dont think even 1 micro amp could get that much... but i am not an expert...... niether is whoever sold these... Thread Starter #### Dr.killjoy Joined Apr 28, 2013 1,196 I wasn't planning on make a battery pack but more or less for ideas for uses on the 18650 cells. A while ago I looked into making a power bank from scratch .. But I got pretty shot down cause the pcb design issues with smps and I am still a noob.. I already have a couple battery packs that use 2 18650 but I wanted something larger and everything of good quality is around$50 more or less and it seem alot IMO. The cheaper units have great and bad reviews but not sure worth the risk and or repair..So I have a bunch of 18650 cells just hanging around.. I am toying with the idea but can't decide to make or not (Oh I have junk phones to test on too lol)??

Units I was looking at
http://www.amazon.com/gp/product/B00ZZSA4SA/ref=s9_al_bw_g107_i5
http://www.amazon.com/gp/product/B00ZZN6J0W/ref=s9_al_bw_g107_i4
http://www.amazon.com/KMASHI-15000m..._cp_107_1?ie=UTF8&refRID=0R37WE3S7KF9GMBZ1S9J
@ScottWang
Thanks and I was checking them out but found it cheaper to buy one with cells installed
@Dodgydave
No problem