# Bloated LiFePO4 cells



## onegreenev (May 18, 2012)

Wow. I have a 12 volt setup using 4 100ah LiFePO4 cells for an aux battery. I have been using it for powering the JLD 404 and JLD Volt meter and to power the contactor for bottom balancing my cells. I did my last cell the other day but left the JLD404 connected to the Aux batteries. Yesterday they were fine and the Aux battery was sitting at 12.6 volts. That means the cells are around 3.15 volts per cell. Two cells were a few tenths different than the others but pretty much the same. Being that the JLD was only powering the led lights on the meter I figured I could leave them for a few days before doing a little testing for capacity. I went out this evening to find all 4 cells bloated real bad. No heat just bloated. I checked the voltages and two were in the millivolt range and the other two were around 1.2 volts. I have seen this bloating on discharge with super high currents but never seen it with a load that was only the JLD and nothing turned on. Just plugged into the Aux cells. All connections to the setup were turned off and there was no way for any thing to cause a hard discharge. It has been sitting for three days so far and for the first two days the voltage was stable in the Aux cell. Only this evening did I find them bloated. 

Any one gander to take a stab at why you'd get bloating like this with no real load. I could see over a very long time that it would drain the cell to zero voltage but what caused the bloating? I have a cell that has a soft short and it is discharging slowly but it has never bloated and it has gone into the millivolt range 

I just don't know why the two cells that are in a positive voltage bloated. I can understand the the ones that went into reversal and then discharged into the millivoltage range. 

I'll get a couple pictures up in the morning with good light. I'll show the setup. I'll show the voltages. 

Pete


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## skooler (Mar 26, 2011)

FWIW....

I used to have a four cell, 60AH LiFePO4 pack as an AUX battery.

It had taken some abuse from a faulty DCDC which drew it flat (bottom balanced at the time). On testing with the powerlab all cells were all over 62AH.

I then switched to top balancing as it apparently stops the cells from being damaged while effectively being float charged when the DCDC is running. voltage terminates at 13.2v (3.3vpc) which is slightly undercharged. 

The main reason for switching to top balancing on the AUX pack was curiosity rather than functionality. I had read about people on here that had success with top balancing , it fits the application so I went for it.

I then went on a 4 week business trip, parked the car up and forgot all about them. The parasitic loads on the car drew them down to below 1v (whole pack)

I gave the car a jump (to get the contactors on the DCDC to close) and drove off absolutely fine.

The pack became troublesome. I found that after charging with the DCDC it would drop to 8v within a few hours. I eventually removed it from the car (it was in a clamped bracket) and placed the cells in the middle of the workshop, away from eachother and anything else. Two of the cells have swollen to DOUBLE their original width and the other two have visible swelling.

The two failed cells were the ones that had the lowest capacity when previously tested.

These cells had no real load when they were drawn down (parasitic on the car is virtually nothing. 10th of an amp at the most?

I suspect being out of balance at the bottom is what killed them. 

I have since replaced with a small LA SLI battery and it has been faultless.


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## piotrsko (Dec 9, 2007)

I have found that if you get voltages above and below the " safe " cutoff, cell bloat becomes a reality on my RC stuff. Typically thrashed a pack. I'm told that the oxides formed occupy a much larger area and thus they swell.


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## onegreenev (May 18, 2012)

Time to dissect another cell to see if that is true. If the oxides formed are larger and cause the swelling then the packs within should be swollen. Last swollen cell I dissected had no such swelling of the pouches within the cell. Those were cells that were reversed and lost when a low capacity cell was within the pack. 

I am more interested in the knowing what the mechanism is that caused the swelling on such a low voltage draw. And why two cells that did not reverse got swollen. I have had cells in the millivolt range that popped back with no problems. Still being used in another 12 volt pack.


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## skooler (Mar 26, 2011)

piotrsko said:


> I have found that if you get voltages above and below the " safe " cutoff, cell bloat becomes a reality on my RC stuff. Typically thrashed a pack. I'm told that the oxides formed occupy a much larger area and thus they swell.


Which chemistry is your RC stuff?


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## onegreenev (May 18, 2012)

As I said here are the photos. I did open one of the cells top seal. There is for sure pressure within. So with that I will say that there is no bloating of the actual cells. If I could get the pressure out and clamp them I'd bet that they will still work. All cells show a positive voltage above the millivolt range. I'll check again later.


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## skooler (Mar 26, 2011)

onegreenev said:


> I am more interested in the knowing what the mechanism is that caused the swelling on such a low voltage draw. And why two cells that did not reverse got swollen. I have had cells in the millivolt range that popped back with no problems. Still being used in another 12 volt pack.


I wish I knew the answer to this too... Lithium batteries seem to be one of the few scientific areas where nobody can actually claim to know everything / be an expert. There is so little publicly available documentation, academic papers etc and what is available appears contradictory and some of it incorrect.

In my experience, anyone that claims to be an expert when it comes to lithium batteries is lying.

Pete,

Please investigate and post your findings!


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## GerhardRP (Nov 17, 2009)

onegreenev said:


> <snip>
> I am more interested in the knowing what the mechanism is that caused the swelling on such a low voltage draw. And why two cells that did not reverse got swollen. I have had cells in the millivolt range that popped back with no problems. Still being used in another 12 volt pack.


Did you measure the actual current draw by the items which were connected?


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## onegreenev (May 18, 2012)

The only thing attached was the two meters. Nothing else was connected. I do not know the current draw from the meter on its own with nothing connected. Not sure if I can measure that with what I have. I can't imagine it being much. Apparently those meters DO draw a considerable amount of current. My Aux pack sat that way for two days without issue. The next day I found what you see.


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## dougingraham (Jul 26, 2011)

I am no expert but around 2002 when I was developing a RC hobby charger for LiPo cells we got to question an electro chemist about some of the failure conditions. When you overcharge or overheat the the electrolyte will out gas and cause the pouch to puff. When you overdischarge and leave it that way gas is slowly produced while the copper foil is being consumed. I was told that after about a month at voltages below 2.35 all the copper is turned into some form copper salt. The longer you leave it below 2.35 volts the worse things will be. And after about a week the cells are unusable for anything. The LiPo cells are not exactly the same as LiFe but they are more similar than different in the failure modes.


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## onegreenev (May 18, 2012)

Im interested in the gassing from low current over discharging. I can understand the overcharge and the heat it creates that can cause outgassing. But it has to be a chemical reaction of some sort that causes cold gassing when over discharging. Whats interesting is that cells with soft shorts don't bloat even though they discharge to the low millivolt levels. I have one that was found to be in the millivolt level and I charged it up and it gave me 107ah out. Then it sat and sat and sat for a week and slowly leaked but has pretty much stabilized at 2.334 volts. No bloating. It is a CALB SE cell. 

So what is the over discharge process that causes swelling? That is the question.


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## EVfun (Mar 14, 2010)

That actually makes sense Doug. I have heard a number of experts talk about a copper reaction at low terminal voltage. It would explain how the cell can appear pretty normal when charged, which is typically pretty low current compared to EV level discharging. That could be tested with a high current discharge. If copper is being lost the internal resistance should go up.


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## onegreenev (May 18, 2012)

How do you check for resistance? I can then check a good cell vs a bad one. I'll take the worst one and open it up to have a look at the copper foils. I can take a small piece and put it under the microscope.


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## onegreenev (May 18, 2012)

> I have heard a number of experts talk about a copper reaction at low terminal voltage.


 Copper reacting with what? Would that cause outgassing? Im assuming copper with lithium causing a redux process even under low voltage and current levels.


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## EVfun (Mar 14, 2010)

There is a lot of stuff to react with inside a cell. There is potential between copper and aluminum and Lithium and no rule that primary batteries cannot use non-aqueous electrolyte. Jay Whitacre talked about the potential for side damage if left at low voltage in that video I think we all watched, but he wasn't specific. Other sources have mentioned the risk is to the negative current collector too. They quit making that aluminum because reactions between aluminum and graphite where life limiting.

I test internal resistance by subjecting a cell known to be at 80-90% SOC to a fast discharge for 10 seconds or more and noting terminal voltage. It can be done with two different rate discharges, if they are suficiently different.

HTH, keep up the good work, I'm looking forward to learning more. I'm back in full swing beating on my LiFeYPO4 pack. This year it has no regs, top balance, but only charge to 3.4vpc -- oh, and adding another of the same except cycle count cells.


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## Semper Vivus (Apr 13, 2011)

Hello,

At cell voltages below 2V, the copper of the anode starts to dissolve into the electrolyte. While recharging again the copper ions can end up as metallic copper within the cell. So there is a risk of internal shorts.

Regards
Tom


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## onegreenev (May 18, 2012)

Thank you for that information. I think it needs to be in the forefront so others know that they need to keep the cells above 2 volts. Id even think it would be a problem then if you sagged your cells under hard loads below 2 volts. Time to reset my controller. I guess I won't be hitting my cells so hard anymore.


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## Semper Vivus (Apr 13, 2011)

Forgot the link (top of the site):
http://www.mpoweruk.com/lithium_failures.htm


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## onegreenev (May 18, 2012)

Thank you. Very good information.


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## Ivansgarage (Sep 3, 2011)

Hi Pete I was thinking about lith for my aux pack, but I think
I will stick with good old sla, Sure is a hell of a lot cheaper.


Ivan


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## onegreenev (May 18, 2012)

I guess this is the reason my Leaf still has the Lead Acid battery.


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## dougingraham (Jul 26, 2011)

onegreenev said:


> Thank you for that information. I think it needs to be in the forefront so others know that they need to keep the cells above 2 volts. Id even think it would be a problem then if you sagged your cells under hard loads below 2 volts. Time to reset my controller. I guess I won't be hitting my cells so hard anymore.


Pretty sure this is resting voltage under 2.3 volts, not sagged. Basically the battery has to be really dead.


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## onegreenev (May 18, 2012)

Yes thats so but I am not taking chances with my cells. Im still baffled by how fast it went from 3.1 volts to Bloatville. In less than a day only connected to a meter that was doing nothing except showing the voltage of the Aux. 

I will be a bit more careful.


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## EVfun (Mar 14, 2010)

That confuses me Pete. Didn't you have pretty good luck taking cells that had rested at very low voltages, charging them up, and putting them back into service? That leaves a question of what combination of events leads to rapid death. Jack has demonstrated that bottom balanced packs can be run low and recharged successfully.


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## onegreenev (May 18, 2012)

Yes, it is terrible confusing. I have had great success with the cells and even with cells that have been quite low. Im afraid that maybe that success is not so good after all. Maybe some of the low cells still held power that I was able to use but serious damage was waiting within. The cells that just died were all good from the start. That is where the other confusion comes from. When I left the Aux connected I checked the voltage every day for three days. The 4th day they were as you were shown. Just plain sucks. Im trying to figure out the events that lead to the rapid death and bloating. Lots of gassing. All were quite cool. Nothing over ambient temps and temps were in the upper 80's.


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## onegreenev (May 18, 2012)

> Jack has demonstrated that bottom balanced packs can be run low and recharged successfully.


Actually he only said. I never saw a demonstration but I do believe he took his cars pretty low without issue. But I have taken my pack to just over 2 volts open circuit with no ill effects. The car at that point is pretty sluggish and crawling. But the cells were still over 2 volts static. That is different than below 2 volts static which I am quite sure happened. It is known by graphs that below 3 volts there is not much left but a few AH's. I presume at this point that the meters take enough to eat up a few AH's even though nothing is connected except the meter. I have to put together another Aux with the remaining good Hi-Powers I have left. Once done I will do a current check to see if I can measure current drain from the meters as they were when the bloat happened. I will report my findings.


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## azdeltawye (Dec 30, 2008)

onegreenev said:


> As I said here are the photos.....



Well I guess that clamping hardware (plates and straps) that is supplied by some of these cell mfgrs might not be such a bad idea after all...


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## dougingraham (Jul 26, 2011)

azdeltawye said:


> Well I guess that clamping hardware (plates and straps) that is supplied by some of these cell mfgrs might not be such a bad idea after all...


Sure it is a bad idea. Pete might not have known his cells were gone until he tried to use them if they had been strapped. The straps just hide the damage, they don't stop it from happening.


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## onegreenev (May 18, 2012)

Correct. Strapping will not prevent any damage and if severe enough could create enough pressure to blow the top caps. They are just screw on caps with o-rings. Im sure mine would have blown.


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## kennybobby (Aug 10, 2012)

onegreenev said:


> ... But I have taken my pack to just over 2 volts open circuit with no ill effects. The car at that point is pretty sluggish and crawling. But the cells were still over 2 volts static. That is different than below 2 volts static which I am quite sure happened. It is known by graphs


The ill effects may not appear immediately, but the damage is irreversible. We saw a bloated cell on Paul's Toyota Celica (44 100A-Hr) that occured several months after he drove his bottom-balanced pack down past the sluggish/crawling stage until it quit moving (pack voltage in 80's). When we dissected the cell all the copper was gone from the anode sheets and the cell was a dead short. The pack was still able to function at a lower voltage with 43 good cells, but was also being overcharged as if it had 44.

From the mpower site:


*Under-voltage / Over-discharge
*Rechargeable Lithium cells suffer from under-voltage as well as over-voltage. Allowing the cell voltage to fall below about 2 Volts by over-discharging or storage for extended periods results in progressive breakdown of the electrode materials.
AnodesFirst the anode copper current collector is dissolved into the electrolyte. This increases the self discharge rate of the cell however, as the voltage is increased again above 2 volts, the copper ions which are dispersed throughout the electrolyte are precipitated as metallic copper wherever they happen to be, not necessarily back on the current collector foil. This is a dangerous situation which can ultimately cause a short circuit between the electrodes.


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## EVfun (Mar 14, 2010)

dougingraham said:


> Sure it is a bad idea. Pete might not have known his cells were gone until he tried to use them if they had been strapped. The straps just hide the damage, they don't stop it from happening.


It might allow them to recover better/more after an incident that cause bloating. If the bloating is because the individual layers of positive plates, separators, and negative plates, move apart from each other the internal resistance should get real high (lack of physical contact), where that might be largely prevented if they where clamped.


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## onegreenev (May 18, 2012)

The inside packs are wrapped pretty good already. My first dissection of a cell showed no bloating of the internal packs. The bloating is only from gassing. Not from mechanical reasons. Once there is gas there will be gas. I don't believe there is a mechanism for the gas to reintegrate. If there is then I would say clamp them. The gas may not be much but just enough to bloat the cell but maybe the cell is still OK. I will be charging one here soon. I was going to find a way to make a good tool to open the top. I can open the tops but the plastic is soft and strips out easy. I was going to drill a couple small holes without drilling through then put pressure on the cell so when I open it the cell will flatten out then quickly tighten the cap again. I would do this in a way air is not going to get in. Just put a super heavy weight on and lightly crack the top enough for the gas to leak out then shut it up. After I suspect maybe there will be some good luck. The caps are pretty thick so I think my idea will prove out well. 


Pete 

More fun to come. I should be able to do some of this in the next couple days. Busy at work and busy getting ready for surgery.


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## Ivansgarage (Sep 3, 2011)

Hey Pete just put a piece of 2x6 on it and park the car on it over night,
see if that would take care of some of that bloating feeling.

Ivan


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## EVfun (Mar 14, 2010)

onegreenev said:


> The inside packs are wrapped pretty good already. My first dissection of a cell showed no bloating of the internal packs.


That is cool to learn. I would have thought the expanding bubbles would have seperated the layers internally. How are the cells packed inside the casing?


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## onegreenev (May 18, 2012)

I'll show you. Gotta find some time to take one apart again. I no longer have the images from a few years ago. They are not wrapped as nicely as the CALB or TS cells. The Hi-Power cells are pretty cheap.


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## onegreenev (May 18, 2012)

Here you go. I found my pictures. I will still tear apart another for better photos but this should do. The carbon layers on the foils are very thin. I originally thought it was an issue with the mechanical swelling of the carbon but it was only gas. The 100ah cells have two 50ah wrapped packages within. This is set of photos is of one of the original Hi-Power cells I ruined by reversal and ran lots of amperage through them. The cell was at 0 volts. I killed it but good. 

Pete 


http://greenev.zapto.org/greenev/GreenEV/GreenEV_Productions_Photo_Albums/Pages/Hi-Power_Photos.html


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## EVfun (Mar 14, 2010)

Cool pics. What was that wrapping material? It looks a bit like poly film that is commonly wrapped around the contents on pallets to keep boxes from falling off. It looks like there was gas in that cell.


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## onegreenev (May 18, 2012)

That cell was a seriously fat piggie. A bit fatter than the ones I showed the other day. I lost two in that incident. Yes, it gassed up pretty badly. It was clamped in the pack the day it happened. I felt the pack and found that area was just screaming hot. Like, hot enough to almost self ignite. As soon as I released the clamp pressure those two cells just popped out like to fat round piggies. 

Yes, I think it is poly film. 

Pete


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## onegreenev (May 18, 2012)

Here is a Thundersky Opened.


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## pm_dawn (Sep 14, 2009)

One very simple way to reduce pressure in the cell is to clamp it really hard (vise clamp) and then unscrew one of the terminal nuts a little (2-3mm) the gently press the terminal down into the battery. 
That will release the gas without the need of opening the valve.
I have done this on ThunderSky and Winston cells.
It should work on Hi-Powers to.

The valve is usually stuck really hard and will probably not vent.
I had a TS160ah Bloat up really bad and actually vent through a hole in the side.
It dit not vent in the valve.

REgards
/Per


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## kennybobby (Aug 10, 2012)

i wonder if the useless so-called 'relief' valve could be drilled and tapped for a schrader valve fitting such as used on air conditioning, then you could attach a hose from a vacuum pump and evacuate the cell? Seems like this sort of thing should be done at the factory since humid air is not cell-friendly...


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## onegreenev (May 18, 2012)

The top plugs are not VENTS. I actually have thought of using a valve then evacuate with my vacuum pump. Problem is that you'd have to keep the cell in an O2 free container until you could put it back on the cell. I'd hate for all that moisture and water and O2 to get into the cell. If you were to use a valve then it would have to be one that would last a very long time with out failure. I prefer to put in holes that I can insert a tool that will do the job better than the current way. That plastic is just cheap. I even thought of having new plugs made with a stronger better plastic and then just put the cells in an O2 free environment and just replace the cells. Put a bit of squeeze on them before doing that to ensure a nice tight fit. I'll just do what I said with my cells first to see how well it works. Test first before diving in too deep.


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## pm_dawn (Sep 14, 2009)

Well I haven't played that much with the Hi-Powers.
But I know for sure that the Thundersky/Winston have valves and not just plugs. If one is lucky they work, but most of the time they don't.

As for not getting moist and air into the cell, I just gave you a really good method on how to get the gas out without opening the plug.

I hope I don't have to do an instruction video for you.

I will clarify it even more if it was hard to grasp to last time.

1. Put the cell upright

2. Clamp the cell REALLY hard. (Hydralic press with thick steel plates on the sides of the cell would be perfect, but a good vise or c-clamp will also do.)

3. Loosen one of the terminal nuts. (About 2-3 mm will do.)

4. Gently press the loose terminal downwards into the cell until you hear the gas being released from the cell.

5. Retighten the terminal nut.

6. Let the cell sit in the clamp atleast over night.

Done!


Regards
/Per


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## pgt400 (Jul 12, 2008)

Yeah, Ive been using Lipos in RC for years....some are just prone to puff. Sometimes within the first month.... Interestingly, I do have a few packs that even after several years refuse to puff even though they have seen more use??????????


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## BVH (Jul 4, 2014)

pm_dawn said:


> One very simple way to reduce pressure in the cell is to clamp it really hard (vise clamp) and then unscrew one of the terminal nuts a little (2-3mm) the gently press the terminal down into the battery.
> That will release the gas without the need of opening the valve.
> I have done this on ThunderSky and Winston cells.
> It should work on Hi-Powers to.
> ...


I just did this with my ThunderSky 100 Ah cells and it worked just as you said it would. I left it clamped overnight and removed my banding and the cells are 95% flat-sided now whereas they were very bulged before. I was surprised at how little volume of gas came out.

I have 16 of these cells that I want to use for powering military and aviation Short arc searchlights in the range of 500 to 1600 Watts (28 Volt nominal so I will use 9-cells) I've tested a few of the cells individually at a discharge rate around that which they will see under normal use to get a representative idea of how much capacity they have and how much run-time I will get. After a full 3.65 V charge and after a .4C discharge rate down to 3.0 VPC, I am seeing between 55 and 63 Ah given. I know that a true discharge test should be done at .1C and am aware that Peukerts factor is reducing capacity but does this seem like a reasonable amount of capacity given the higher rate of discharge?

I guess my more important question is whether these cells are reasonably safe to use given they have been puffed from apparent abuse prior to my ownership? I've read where the Copper Anode material can dissolve back into the electrolyte and cause a possible short condition. I don't have enough experience with these Prismatics to know. I've been using RC Lipos for quite some time and wanted to get away from their "Rapid vent with Flame" potential.

My intent is to find the 9 highest capacity-matched cells and to make my pack using them. I got these cells for nothing so if they are "trash" then so be it.


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## Phaser (Jul 20, 2014)

Hi, everybody.
Inflate LiFePO4 cell is very easy 









Just a little bit longer keep a charged battery on the max. voltage ...


Very nice explanation is here: Long holding the voltage after charging.
http://auto88.cz/_info/Doc/GWL-Power-Cell-Damage-OverCharge.pdf

Phaser.


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## MN Driver (Sep 29, 2009)

Accordian battery.


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## onegreenev (May 18, 2012)

That was an awful lot of batteries to learn that lesson. We have tried to tell folks but they just don't listen. You keep the charger on the cell and have the voltage above the safe limits they will die. Also they will die on the bottom if allowed to go below the safe limit.

Mine were slowly discharged under almost zero amperage but they still died and bloated like yours.


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## Phaser (Jul 20, 2014)

onegreenev said:


> That was an awful lot of batteries to learn that lesson.


Yes it is unfortunately true, one learns from mistakes, but also occur sometimes inexplicable errors. When everything is complied with and still it happens that the battery will die.
Lots of examples of lessons can be found here:
http://gwl-power.tumblr.com/tagged/accidents

It is necessary to simply monitor everything always as well with some electronic circuit and not to rely only on its own inspection.
One can easily make a mistake, or while not paying attention
and a lot of money's gone ...
Very cheap and simple circuit - CellLoger
http://www.ev-power.eu/_d1747.html


But as you say ...
"folks just don't listen."


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