Li Ion packs I made from surplus cell phone batteries - RC Groups
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Mar 13, 2004, 04:54 PM
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Li Ion packs I made from surplus cell phone batteries

I bought these surplus cell phones batteries on ebay. I got 18 cells for $36. I broke open the packs and there were 2 cells and some circuits in each battery pack. I pulled the circuit boards off and soldered 3 cells in series. these are the Qualcom packs I used...
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Mar 13, 2004, 04:56 PM
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This is the pack with 3 cells...
Last edited by daveoner; Mar 17, 2004 at 09:11 PM.
Mar 13, 2004, 04:57 PM
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Has anyone ever used Plasti-Dip instead of shrink wrap to coat your packs?

This is the pack after three coats of plasti dip...
Mar 13, 2004, 04:58 PM
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This is a close up of the qualcomm pack...
Mar 13, 2004, 05:06 PM
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The entire hard shell of the battery is the negative terminal. You can solder negative side on anywhere. But you have to use insulator between each cell. I used double sided carpet tape in 3 built up layers. The case has to be shink wrapped or dipped in plasti-dip so that it will not short in case it is toched on metal.

The li-ions are probably 25-50% heavier than lipos but actually this pack weighs in at 5.0 ounces. The pack is 1800 mah 3 cell. (12 volt)
I did not have comparable lipo to compare but my 1200 mah etec is 2.9 ounces and when I add a 640 mah kokam, the two together (1840 mah)weigh more than 5 ounces. This weight comparison was done just outta curiosity. I built 3 of these packs so far. & will be using them in my slow stick
Mar 13, 2004, 11:01 PM
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Is there any indication on the individual cells what brand they are? Below is a link to the spec sheet for the Panasonic 1800mAh prismatic. You'll notice in the discharge characteristics that the 2C (3.6A) discharge is not substantially different from the 1C and .2C discharge curves. This is good, as earlier prismatics dropped off pretty badly at 2C, sometimes delivering less than half the capacity that they did at 1C. If the cells you have are Panasonics, or another brand with similar performance, they should be pretty good at 2C. If they are off-brand cells, they might not be so good.
Mar 14, 2004, 12:54 AM
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I lied about the mah rating. Turns out they are only 1150 mah.
I don't see any brand name on the cell.

I will be doing some half-baked testing and I will post my results
Mar 14, 2004, 05:26 AM
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Daveoner I got the same batteries on Ebay and I built 3S packs and I had them in my Piccolo Heli and after a couple of flights they just crapped out on me. I have a couple left that I plan to build a couple of packs for my slow stick and my mustang but before I fly with them I plan to test them a couple of times to see if the same thing happens again with the motor setup that I will use in my Slow Stick.

The Etec 3S 1200 pack that I use now in the heli has about 50 runs and is almost 18-22 mins for each flight where the qualcomms decreased with flights really fast but I might be pulling more juice than you would and have ruined 3 packs that way.
Mar 14, 2004, 10:45 AM
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If they are the older 1150s, they will probably have problems delivering decent perforance at 2C (2.3A). They might work OK for sub-2A IPS applications, but nothing more.
Mar 14, 2004, 10:38 PM
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My power system is an AXI 2212/34 with cc phx 25. This morning (and three to five flights this week) I used my etec 1200 3s, two kokam 640 (in parrellel) and I tried for the first time a 2 cell sony li-ion 1350 mah(also from ebay *blue cylindrical cells*). I noticed the difference with the 2 cell li-ions as it took nearly full throttle to take off, where with the 3 cell lipos it takes off at half throttle.

I flew my slow stick for a short flight this evening using this here home-made 3 cell li-ion. And although the top speed of the prop was similar to my lipos (if not higher) it was obviously a bit more sluggish on take-off. (being 2 ounces heavier and all). It was only a short flight at dusk, but so far I am happy with the performance.

Based on what you guys are telling me I expect that after five flights I will see some decreased performance. If the cells crap out on me I will post those results.
My testing is not at all scientific. Electric flight is new to me & I only have 6 or 7 flights on my slow stick. The little outrunner is alot of motor for the SS, so I usually putt around at 1/3 throttle. This may result in the cells lasting longer.

Does anyone have any suggestions on how I might follow a more scientific testing regimen?
thanks to everyone for your input.
Last edited by daveoner; Mar 14, 2004 at 10:43 PM.
Mar 14, 2004, 10:48 PM
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I use a Plantraco dedicated LIPO charger. It has 50/100/200 & 400 mah charge rates. I usually charge at the lowest (50mah) setting to save my cells and because I am patient. It also seems to get every last bit of "juice" into the cells.
Mar 15, 2004, 02:22 PM
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Today I flew the SS with the 3 cell li-ion pack. After a 20 minute flight (mostly 1/2 throttle) I decided to change packs but there was still lots of juice left. I did notice a difference when I put a fresh pack in but the 20 min flight was without problems. I did a few WOT loops but mostly 1/2 throttle and basically NO power-off gliding. My CC 25 amp has a low voltage cutoff which I believe is set up correctly for 3 cell lithiums and the LVC never kicked in. I am happy with the packs so far.
Last edited by daveoner; Mar 15, 2004 at 02:37 PM.
Mar 17, 2004, 09:10 PM
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Is slightly warm unsafe condition for LI-Ions?

Yesterday I flew and tried to go wide open often and after 20 mins plus the pack was slightly warm, but only a few degrees it was very comfortable to the touch.

Is slightly warm bad for LiIons? Is it bad for Lipos?

Apparently not:
Last edited by daveoner; Mar 17, 2004 at 09:27 PM.
Mar 17, 2004, 10:59 PM
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Warm is OK. Hot is marginal. Uncomfortably hot to touch is bad.
May 12, 2004, 08:15 PM
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Packs still holding up.

I usually cut off after about 20 minutes but have done 25 minute flights with my (fast) stick. I call it a fast stick because I am using an AXI 2212/34 with 1170 prop. The qualcomm packs are still holding up. I also tried an AXI 2212/26 which draws more amps & actually noticed (for the first time) my packs will drop voltage after 20 minutes. So 25 minutes on the Slow (fast) Stick with AXI 2212/34 and 20 with the 26 turn motor. My stick is otherwise stock, but I will be building one with a symmetrical wing and an extra servo or two soon.

While looking for (my own) thread, I noticed a few others have posted threads where they are being challenged by moderators and others to show proof of their results. I am not an expert but I have read all the safety precautions and try to not "tax" my batteries too much. These packs only get moderatley warm with the 26 turn amp hog. Not even warm after 20 minutes with the 34. My stick is probably 15 ounces. I dont know what I am drawing but it seems to be working.

I actually placed another order on ebay for 24 cells ($33.94 shipped) I can make 8 more 3s packs and I actually prefer these to my lipos. Lipos seem to be too fragile. If a lipo pack crashes it may be deemed unusable.

If anyone reads this and can tell me approx what I am drawing with an AXI 2212/34 on an otherwise stock slow stick can you please post. I think these packs are performing better than 2c. (whatever that means )
Last edited by daveoner; May 12, 2004 at 08:17 PM.

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