Lipo Bags Rule OK!

[MattyB]

Posted by Bill_B on 04/07/2017 11:45:43:

Just out of curiosity I wonder what brand and capacity the batteries were that failed in the OP?

Probably more important what was the age and usage pattern. Had these cells been consistently stored at full charge for long periods?

[Bill_B]

I'm not totally convinced that storing LiPo batteries part charged is necessary if they're being used fairly regularly. I always check and then charge mine fully after a flying session so they're ready at a moments notice. Some times it can be up to three weeks before they're used and a couple of my smaller packs (3s 2200mAh) are nearly three years old and haven't exactly had an easy life. Admittedly they're just slightly puffy, but none (to date) have spontaneously combusted. Personally I think most problems are due to careless handling and use.

[The Wright Stuff]

But when we're talking about small number statistics, personal experience is not sufficient to get insight. It's like saying:

"Last week I bought a lottery ticket but didn't win the lottery, and the week before, I didn't buy a lottery ticket and didn't win the lottery. Therefore buying a ticket makes no difference to my chances of winning the lottery"

If there is any way I can store LiPos in a manner that means an already vanishingly small probability of spontaneous combustion is turned into an even smaller risk, then I'll take it. I only have 3S up to 3300 mAh. I don't really care about the battery life. To be honest, I don't really even care about my models all that much. I do care about my house, my life, my wife and baby daughter...

[MattyB]

Posted by The Wright Stuff on 04/07/2017 15:05:56:

But when we're talking about small number statistics, personal experience is not sufficient to get insight. It's like saying:

"Last week I bought a lottery ticket but didn't win the lottery, and the week before, I didn't buy a lottery ticket and didn't win the lottery. Therefore buying a ticket makes no difference to my chances of winning the lottery"

Yep, completely agree. Personal experiences area extremely unreliable measure when it comes to battery performance simply because the way they are used and stored is hugely impactful on their life and performance. Anyone who says "these packs are great, but those are rubbish"

Posted by The Wright Stuff on 04/07/2017 15:05:56:

If there is any way I can store LiPos in a manner that means an already vanishingly small probability of spontaneous combustion is turned into an even smaller risk, then I'll take it. I only have 3S up to 3300 mAh. I don't really care about the battery life. To be honest, I don't really even care about my models all that much. I do care about my house, my life, my wife and baby daughter...

Yes, that is the key point here - if you want the safest option you MUST store at lower voltages to reduce the available energy in the event of a fire. At 3.7V/cell there is next to no energy left in the pack and you could quite put a nail through it with only a mild fizzing the result; try that with a fully charged pack and you will get a very different result.

[Bill_B]

Is it recommended to store Li-ion batteries part charged too?

[MattyB]

Lipos are Lithium-ion packs. Do you mean LiFe (Lithium Iron)? Confusingly they are Lithium-ion too! I admit I have not used LiFes as power packs so don't know a huge amount about them, but from what I understand they are much more resilient to storage at elevated SOC. Having said that one of my cheapo HK LiFe soft RX packs swelled and died within 6 months of purchase, though I suspect that is much more likely to be a QC issue (my others have been fine).

Edited By MattyB on 04/07/2017 17:06:51

[gangster]

Now I know why I have gone back to glow

[Bill_B]

Posted by gangster on 04/07/2017 17:54:08:

Now I know why I have gone back to glow

That's not really a relevant comment In my humble opinion, but seeing as you've taken the time to post, I'll reply: You've gone back to glow power to have an irritatingly noisy vibrating model that gets covered in sticky gunge, obliges with the occasional dead stick, burns out plugs, needs the carb tweaking if the temperature/humidity changes and needs a hernia inducing field support box. Sure electric power isn't perfect either, but I can't see the attraction to glow if only for the afore mentioned reasons.

Each to his own though.

Edited By Bill_B on 04/07/2017 22:07:57

[simon burch]

Li-po are Lithium polymer, not Lithium Ion or Li-Fe. Li-Fe packs are not as volatile (plenty of videos of people trying to get them to explode like Lipo's on YouTube). Different chemistry and voltage per cell.

Simon

[gangster]

Hi Bill totally agree on all points you made. But this is an important thread and I will comment no further so it keeps on track

[MattyB]

Posted by simon burch on 04/07/2017 23:39:40:

Li-po are Lithium polymer, not Lithium Ion...

Simon

Not according to Wikipedia or Battery University...

"A lithium polymer battery, or more correctly lithium-ion polymer battery (abbreviated variously as LiPo, LIP, Li-poly and others), is a rechargeable battery of lithium-ion technology using a polymer electrolyte instead of the more common liquid electrolyte. High conductivity semisolid (gel) polymers form the electrolyte for LiPo cells that are being used in tablet computers and many cellular telephone handsets."

"To make the modern Li-polymer battery conductive at room temperature, gelled electrolyte has been added. Most Li-ion polymer cells today incorporate a micro porous separator with some moisture. Li-polymer can be built on many systems, the likes of Li-cobalt, NMC, Li-phosphate and Li-manganese, and is not considered a unique battery chemistry. The majority of Li-polymer packs are cobalt based; other active material may also be added.

With gelled electrolyte added, what is the difference between a normal Li ion and Li ion polymer? As far as the user is concerned, lithium polymer is essentially the same as lithium-ion. Both systems use identical cathode and anode material and contain a similar amount of electrolyte."

Edited By MattyB on 06/07/2017 15:51:55

[Allan Bennett]

Hobby battery manufacturers and suppliers seem to use the term "ion" for any lithium battery that they don't know, or won't tell, the formulation of. "ion" is simply an atom or molecule with a net electric charge due to the loss or gain of one or more electrons so, as a battery description, it tells us nothing about the chemical make-up, which includes those which Mattyb has mentioned above.

 

P.S. What I'd like to know is what brand that LiPo bag is, for it seems to have successfully contained a 4-LiPo fire without letting it spread to adjacent flammable material.

Edited By Allan Bennett on 08/07/2017 08:08:19

[Old Geezer]

.Yesterday evening SWMBO smelt hot plastic in the conservatory - she'd read somewhere about the potential fire risks with LiPos and suddenly twigged we'd got a few LiPos in my Office, no - I won't say how many - but if she counts and values 'em I'm in REAL trouble.

Anyway - we had a "little chat" - and they're now in a weatherproof box in the garden.

So a couple of concerns, if stored outside how cold can LiPos be stored (charged) without them coming to any harm? Indoors ammo boxes might seem a great idea, but if a LiPo self destructs inside an ammo box, if gas tight is it going to go off POP, and if not gas tight won't you get at the least some pretty bad smoke damage?

[The Wright Stuff]

A 2 mm hole drilled in the box appears to be the consensus.

[Denis Watkins]

When heavy bombers passed over a target, the 1st bombs blew the roofs off,

But subsequent bombing did little damage as the blast was not contained

So relieving some pressure should do the trick

[Dave Hopkin]

Posted by Gurth Scriven 2 on 21/07/2017 15:48:24:

So a couple of concerns, if stored outside how cold can LiPos be stored (charged) without them coming to any harm? Indoors ammo boxes might seem a great idea, but if a LiPo self destructs inside an ammo box, if gas tight is it going to go off POP, and if not gas tight won't you get at the least some pretty bad smoke damage?

Temperature wise external storage should not be an issue as they can be taken down to -25 with no damage PROVIDING they are allowed to warm up to room temperature slowly

NATO Ammo Boxes have a rubber seal glued into the lid to keep the ammo dry making them almost gas proof - two ticks with a scalpel to remove a 6mm section of the seal will give you a gas vent.

[John Privett]

Posted by Kevin 216 on 04/07/2017 07:27:49:

IanR try Denbigh Army Supplies www.denbigharmysupplies.co.uk/ they have ...

I guess you really meant www.denbigharmysurplus.co.uk ?

[Gordon Tarling]

Posted by Gurth Scriven 2 on 21/07/2017 15:48:24:

.So a couple of concerns, if stored outside how cold can LiPos be stored (charged) without them coming to any harm? Indoors ammo boxes might seem a great idea, but if a LiPo self destructs inside an ammo box, if gas tight is it going to go off POP, and if not gas tight won't you get at the least some pretty bad smoke damage?

I store all my Lipos in a fridge, at storage voltage. I wouldn't recommend storing them fully charged, as that will shorten their lives and increases the risk of a conflagration. If stored cold, then allow them to come back to ambient temperature before you charge or use them. Relieve any possible pressure in an ammo box by removing all or part of the seal. I wouldn't consider that a 2mm hole would be anywhere big enough to vent the box safely.