Lipo Fire
 

Tonight we had our second lipo Fire.

Fortunately the gentleman who owns the lipo was switched on enough to be using an approved lipo bag whilst charging. Thank you.

Thankfully no damage was done and most importantly nobody was injured!

Please guys take this second warning seriously and make sure we ALL use lipo bags/sacks when charging at all time, even in your own home

Thought last night was much more relaxed (maybe too much :)) but great all the same.

Don't forget if you want me to get involved with the facebook page would be more than happy to do so. I do this for work so it would be easy for me to run this Silverstone one too. Just need admin rights.

Also let me know what you want fishing wise for your client and can sort it out. PM me on that.

No hints as to what caused the fire?
LiPos don't tend to explode for no reason. And knowing why would be far more useful than just telling everyone to use a bag.

Brand new lipo out of packet on first charge at correct amps. So don't really have the answer you're probably looking for. Sorry

First time charge fault
 

When we had the first fire that too was a first time charge, I'm sure I'm right but I will ask Richard just in case?? :blush:

Pete had a brand new LiPo that had a completed knackered cell, we all use the little lipo checkers that you plug into the balance lead so we always know where are on cell voltages etc. The one pete had was checked before putting on the charger so new instantly NOT TO try and charge it else that would have ended up the same as what happened last night.

If you dont have one already this is a very handy piece of kit. I always check before and after it goes in the car and before and after I charge it so I always know the health of my lipos before moving current through it.

http://www.giantshark.co.uk/product/...ipo-meter-2-6s

Hi all,

Can I ask what charger was being used and whether it was a balanced charge?

I am only curious because I am not a massive advocate of Li-Po bags because I prefere prevention to be better than a marketing cure.

Of course, if your batteries are on fire, then a bag to take them outside would be great, but I'd preferred the fire not to have started in the first place.

I am concerned that everyone may think that using a Li-Po bag makes them safe, instead of understanding and minimising the risk imposed in using Li-Po batteries.

There are mainly two scenerios in which you are more likely to have an issue.

Bit of background (sorry if its teaching you to suck eggs)

Li-Po batteries used in RC racing typically consist of 3 cells connected in parallel, connected in series to another 3 cells connected in parallel.

The physical configuration of the batteries doesnt really matter for the point of this, can be saddle, square or stick packs, its all the same inside.

The reason for the 3 cells in parallel is because of the high discharge current required to do the fun hobby we all enjoy, very very quickly.

Typically each individual cell will happily discharge at more than 25C and charge at around 1C. This means that if you had a 5000mAh set of batteries, you can theoretically discharge them at 5000mA x 25 = 125A for a very short period on time (about 60s).

Ofcourse the connectors, battery tabs, wires and solder would fall off but theoretically this is possible. The 1C charge means that you can charge these batteries at 5000mAh x 1C = 5A.

Scenario 1

This all sounds great but if two of the cells inside the battery are no longer connected - i.e. breaks in shipment, manufacturer being terrible, or during vibration whilst using them, then the problems begin.

Back to the example, we had 5000mAh owing to the 3 cells in parallel, two disconnect, now we have only (5000mA/3) = 1666mAh. Then we go and charge them at 5000mA and bobs your uncle you are now charging at 3C.

Cells catch fire or if you are lucky, just swell.

The problem exists in the discharge scenerio, but is less likely to start a fire owing to now the maximum discharge current is 1666mAh x 25C = 41A which cars might get close to, but only for a small part of the track. This also explains why most issues are on the bench, not on the track. Typically, on the track incidents are caused by unlucky vibration, causing mechanical failure of solder joints, which by chance causes issues. Or your ESC being terrible (and from Tamiya in my experience) !!!!

The battery monitoring gadget specified previously will not correct this scenerio, if there is a single cell that remains connected inside the battery the potential or voltage reading will be the same.

The best way to reduce this risk is to always use a charger with a balanced charge whilst charging.

Scenerio 2

Using the same issues in scenario 1, once the bad (or broken) battery has less cells than the good battery thats in series and you DO NOT use a balanced charge, then the faulty battery will get to 4.2V before the good battery.

The charger, is not aware that one battery is at 4.2V whilst the other one is still charging (lets say for example, 3.9V). It only knows the total voltage i.e. 3.9V + 4.2V = 8.1V. The constant current part of the charge cycle will continue to charge the broken battery, which will go over voltage and is most likely to catch fire.

The best way to reduce the risk is to always use a balanced charge whilst charging.

So, from all this writing "or ranting", I suggest everyone uses a balanced charge !!!! It is the safest way to charge the battery packs. The charger will monitor the "middle" voltage and try to balance the cell, which will take ages if its broken, because typically chargers only have 1A balancing current.

This makes a very nice visual (or timely) aid. If it takes ages to charge from a balanced charge, then something is wrong !!!

Li-Po bags do have there place in our hobby, but unfortunately, all Li-Po bags are made from a material which cant be see through. I'd prefere to have a Li-Po bag available to put my batteries in if they did spontaneously decided to catch fire, then walk outside with them disconnected from my charger. This does however mean you also need a heat resistance pair of gloves, but at least you can see what is going on !!!

Cheers

Ads

While on the subject of lipo bags/fires do you store your lipos in bags? Has a lipo fire ever occurred when not on charge?

Thank you
 

Ads, I thank you so much my friend. I haven't had more than 5 hours sleep in one night for probably over 10 years until reading your post.

Seriously though, I know I'm not the smartest chap and will always admit that. But, surly people need to be more educated (which you've kindly done) about Lipos before just being able to buy as many as one likes.

So mate, am I wrong in saying if I balance charge my lipo's every charge and they take longer than usual then I may have a problem?? That's the part I want clarifying please.

Thanks,

Matt

I store my lipos in one of these in my garage. For the sake of about £20 i can sleep soundly without concern of the spontaneous combustion of my home. Although it would seem uncommon, I have heard of a few fires that started when not even charging cells.

https://www.gunpartscorp.com/pub/Pro...ge/1287850.jpg

If I remember rightly from a post on another thred there has been no known case of lipos malfunctioning in storage always during discharge (use) or charge or bad handling (shorting them etc)

there have been instances of lipo packs stored fully charged swelling and eventually combusting, there was a writeup on this in one of the model flight magazines as someone lost their house. normally unless mistreated lipo's are pretty safe really, always balance charge, and always check for bad cells, especially if the pack is new or hasnt been used for some time. i store my less trusted/ less used packs in ammo boxes, make sure you drill a small ventilation hole in them though, as you could get a nasty surprise when opening if there has been a problem and the gases havent been able to escape.

I have always balance charged mine since I started in the hobby. My charger wont charge unless the balance lead is connected anyway.

The battery checker I use, whilst it wont prevent anything as Ads pointed out, it does however show both the individual cell voltages and the total voltage so I can see when one cell is poorly or the 2 cells become out of balance, giving you a heads up before you decide to charge or not.

Thanks Ads, that some very valuable intel.

I noticed as I'm always balancing my cells while charging that a lipo will take more time to balance charge as it's getting used. A new one take about half an hour while my old ones may need an hour to do so.

As far as use and best lifetime of a lipo I was told not to charge and keep the lipo charged, 4h max but best to charge at the track before a run.
Try to avoid too much charge per lipo on one day, at least wait for it to cool down. Better to buy some more and rotate.
Try to avoid running to the cutout at 3.00v from the ESC, a good 5-7mn run, 10mn max. You will work between 4.2 and around 3.7 (storage voltage) meaning a better life from the Lipo and because at the currents we are using (huge) the voltage of the cell come down quite a lot when it delivers big currents, enough to lower the cell voltage. My esc monitor this and below the storage voltage (I would say below 3.6v) the cell voltage go lower than the 3.00v recommended, even for a very short period of time and that change the chemistry of the cell and that's one issue that can cause swelling and puffing.

I'm no expert, but it works keeping the cells punchy and unpuffed along the year and be safe.

I never charge cells at there maximum rating 5100mah charge at 4.8A etc and balance often, never connect without balance plug out and never charge freshly used cells i always rotate so i know, and always go home without fully charged cells.
Its a shame that brand new cells knowing how dangerous they can be, can have faults also.