I have three 7s packs with 14 4ah 10c cells each. I pulled them apart and threw away the ones that are cracked open, bent and read 0v. Still have many that hold a full charge. About half are a bit puffed and half are normal. Are the slightly puffed still usable? Other then soldering them together making a pack is there any way of testing each cell individually?
Puffed cells, still good?
- Thread starter silviasol
- Start date
DAND214
10 MW
I have done the same, only used hot glue to seal them. No leakage or foul smell.whatever said:
I also did a IR test using my Icharger and they are fine.
Dan
dogman dan
1 PW
Those might be ok. but clearly not "good as new".
I suggest a non metallic pin if you try to de puff them with a pin prick.
I suggest a non metallic pin if you try to de puff them with a pin prick.
whatever said:
I was thinking the same thing! I guess if it is proven working I can go ahead with the plan.
drebikes said:
I researched more about testing them last night, I saw the battery university page and none of that is making sense to me. I did find the link below with a more simple way using power resistors. I have a few being shipped from china now, I will have to wait a few weeks which sucks since I am anxious. I hope these 4 ohm 5W power resistors are adequate for these cells being 4ah and 10c.
http://laserpointerforums.com/f67/how-healthy-your-batteries-how-measure-internal-resistance-57576.html
cal3thousand
10 MW
Are those LiFePO4 cells?
They look like this bunch of puffed LiFePO4 cells that I received from a friend. I have (2) 72V 15Ah packs and many are puffed like that and some are even worse. But there's still a good deal of cells that look normal. I was just going to weed out the puffies and high IR cells, but this thread has me thinking about saving some of the better (low IR) puffed cells and making a new pack.
They look like this bunch of puffed LiFePO4 cells that I received from a friend. I have (2) 72V 15Ah packs and many are puffed like that and some are even worse. But there's still a good deal of cells that look normal. I was just going to weed out the puffies and high IR cells, but this thread has me thinking about saving some of the better (low IR) puffed cells and making a new pack.
dnmun
1 PW
so you don't even know if they are lipo or lifepo4? so how do you know they are 10C 4Ah?
Electric Junk
10 W
Poking cells to let gas out them taping them back up, i am so behind on battery technology.
Ykick
1 GW
Check this thread for layman's method to measure Cell IR:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=48739&p=718933&hilit=celllog#p718933
http://endless-sphere.com/forums/viewtopic.php?f=14&t=48739&p=718933&hilit=celllog#p718933
wb9k
10 kW
The gas that forms in A123 cells (Nanophosphate LiFePO4) is mostly CO2 once things in the cell have settled down, so that's not dangerous. I would not poke a hole in a cell to let the gas out. Either compress the cell to push the gas to the margins of the cell (outside the electrode stack), or burst the cell trying. If the cell survives, keep it compressed like that and use, assuming the cell tests good enough for your purposes otherwise (capacity and impedance are most important to capture and should be also tested under compression). If the cell bursts or springs a leak, it's shot. Scrap it.
Ykick said:
I actually have a watt meter. Would a 12v bulb like he is using be safe for a these cells at the 4.2v?
dnmun said:
They are lipo. They are from a goped which actually has batteryspace make their packs. The model number is printed on each cell at the link below
http://www.batteryspace.com/highpowerpolymerli-ioncell37v4000mah6745135-10c148wh40arate-ulunlisted.aspx
Ykick
1 GW
I generally apply the load with a bunch of cells in series so that i can use household 120AC heating elements, soldering irons, etc. as my load. 12V bulb on 4VDC will only pull a fraction of rated current. Maybe 3-4 cells in series for 12V bulb would work? I like to see between 5-10A across my 5Ah RC Lipo cells.
Be creative, small steps. Test, repeat, test again. You'll get there!
Be creative, small steps. Test, repeat, test again. You'll get there!
hydro-one
10 kW
get rid of them is my advice. . take the worst one and take it outside and poke it with a scratch awl. see what could happen to your pack if "something" goes wrong..... you wont mess with puffed cells after that. if it dosent blow then you might be ok but as mentioned, do a discharge test , my favorite is a blow drier or two in parrelel. they only work one polarity, but the wrong polarity wont harm them . give it a shot!! 
Ok I have a few things in mind. I have a 88cfm case fan(spins extremely fast) that I am going to try first. Only problem is I do not know how to calculate the internal resistance. I will see amps and the actual voltage drop, any idea how I would calculate the resistance from that?
I will be keeping a very watchful eye on the packs. I have a smoke alarm and fire extinguisher right next to my scooter and when I leave the scooter always comes with me. The pack will have the same high quality pcm/bms they use in the packs to make sure they don't go over/under voltages.
I actually opened a puffed pack at 0v to look at how it is made, with a full face respirator mask. Basically all it is is a long paper like thing with the polymer lithium folded over and over and the - and + tabs are on the very end of each. I can see how fires would happen, the cell gets too hot to the point the tab part would melt/spark or something and then the paper lining will fry/melt causing the lithium layers to connect in all the layers, making positive touch negative in each layer. Would only be downhill from there. Poking holes in an entire pack wouldn't do much, that is just a small pin hole thru the layers. Melted tabs is 1/2 inch connection that would go thru all layers, more then enough size of a conductor for a electrical fire.
http://www.batteryspace.com/pcmwithequilibriumfunctionfor259vli-ionbatterypackat90alimit.aspx
hydro-one said:get rid of them is my advice. . take the worst one and take it outside and poke it with a scratch awl. see what could happen to your pack if "something" goes wrong..... you wont mess with puffed cells after that. if it dosent blow then you might be ok but as mentioned, do a discharge test , my favorite is a blow drier or two in parrelel. they only work one polarity, but the wrong polarity wont harm them . give it a shot!!
I will be keeping a very watchful eye on the packs. I have a smoke alarm and fire extinguisher right next to my scooter and when I leave the scooter always comes with me. The pack will have the same high quality pcm/bms they use in the packs to make sure they don't go over/under voltages.
I actually opened a puffed pack at 0v to look at how it is made, with a full face respirator mask. Basically all it is is a long paper like thing with the polymer lithium folded over and over and the - and + tabs are on the very end of each. I can see how fires would happen, the cell gets too hot to the point the tab part would melt/spark or something and then the paper lining will fry/melt causing the lithium layers to connect in all the layers, making positive touch negative in each layer. Would only be downhill from there. Poking holes in an entire pack wouldn't do much, that is just a small pin hole thru the layers. Melted tabs is 1/2 inch connection that would go thru all layers, more then enough size of a conductor for a electrical fire.
http://www.batteryspace.com/pcmwithequilibriumfunctionfor259vli-ionbatterypackat90alimit.aspx
Ykick
1 GW
silviasol said:
If all cells are in series then Amps will be the same across all of the cells. What you do is measure resting voltage (either single cell or series string). Apply load for about 10 seconds and note the Vdrop and Amp load. Subtract that voltage (loaded) measurement from the resting V. Divide Vdrop by Amp load and multiply by 1000 - you will then have mOhm IR value for pack or cell. Depending on if you used pack Vdrop or Cell Vdrop. If you measure Cell IR of RC Lipo good ones will be in the 5-15mOhm range per cell. Anything much above 20mOhm per cell is ready for less high drain use (lighting?) or the trash bin.
Hillhater
100 TW
Sorry to be blunt but... if you actually read and watched the video's in the links you were given, you would know all this info ..and more. !!
Hillhater said:Sorry to be blunt but... if you actually read and watched the video's in the links you were given, you would know all this info ..and more. !!
I may be lazy and not have an attention span to watch an entire 15 minute video but I do know now. A long video or a simple math problem?
Well after "some" testing, I am building a pack with what I "believe" is the best cells of the bunch. It will match my other pack I have in the scooter, 7s 8ah(with exact same cells), however that pack is new with less then 100 charges. Being they are 10c would I benefit from running both at the same time(after a few test runs with the single pack) or would it be the same range running one until it is depleted then plugging in the other. It will be running about 35amp so that is almost 5c for one pack and 2.5c if I ran both packs. Is there a "grace" period for a certain C rating that will not cause energy loss? As in will a 5c discharge loose more energy then a 2.5c discharge on a 10c rated pack.
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