Lipo's  

The potential hazards of Lipo fires are well documented on the web and in magazines. We have had at least two fires amongst club members, one after a crash and one through choice of the wrong number of cells when charging but, at least, on these occasions valid causes were apparent. 

 However the following email has been received from David P :

"I did have a nasty scare this week at home when in the middle of the night I thought I could smell burning. A quick look round the house revealed nothing and thought 

it was just BBQ smells wafting though the open windows on this hot night. However, next morning I went into my modelling room and touched a sticky residue on the table and then noticed my lipo storage bag was burnt to a crisp! OMG.....how lucky am I the the bag contained all the heat and didn't set fire to the house. 

I've certainly learned I few lessons this week about storage of these potentially dangerous batteries which may be of help to others. 

Always store batteries in a fire proof bag. Do not leave the bag on a flammable surface.......got myself a large metal box now to put the bag of batteries in. 

Yes I lost about £50 worth of batteries but how easily it could have been so much more. Pleased the bags do what they say they do! "

David's report is significant because of several factors :

- he hadn't used, charged, or even disturbed the batteries for a few weeks

- they were stored indoors at a fairly even temperature

- connectors were Deans-type, shrouded and unlikely to touch and short the batteries

Whilst we may take all the care we can to ensure that our Lipos don't ignite, on some occasions it is clear this can occur for no apparent reason. In addition to taking care of the batteries in storage, transport, charging and use, we should also plan how to protect ourselves and property should a fire occur, since this obviously could happen to any of us at any time. 

Fire protection steps

i) Store the batteries in quality Lipo bags. If the worst occurs then they may save the

day as happened in David's case. 

ii) As "belt-and-braces", store the Lipo bags in a metal container e.g. an ammunition 

box, making sure it's vented to prevent pressure build up. The peak temperatures

involved are enough to eventually melt steel but the fires are relatively short

duration and such a container will always be a safer option. 

See Chris or Dave for advice on these.

iii)  Choose where to store and charge them carefully. A concrete floor in an outdoors

location with no clutter or adjacent flammable material is obviously a safer

location than a wooden bench surrounded by models in a bedroom in the house.  

iv) Lipos degrade with age and this happens faster at higher temperatures. Avoid 

high battery temperatures in use and during storage. Lower storage temperatures

are better than higher ones. Check and observe manufacturers recommendations.

v) Don't store Lipos fully charged, they are safer and degrade less at the "storage" 

terminal voltage of about 3.8V rather than 4.1-4.2V per cell. Chargers often 

have the "storage" setting as a charge option - use it. Also, at the storage voltage

they also have less energy if they go up.

vi) Don't forget transport. A fire in a car could be very serious. At least keep the 

Lipos in a storage bag and, maybe, a metal container in the car. Don't transport 

the batteries to and from the field loose or in a model. The club member referred

to above whose model had crashed was seconds away from loading it into his car

to leave when it went up.

vii) Don't forget that Lipos may be used in other applications e.g. it's common to 

for them to be retrofitted to transmitters. These must be considered just as

hazardous as Lipos in models when it comes to unexplained fires. Store Lipo 

equipped transmitters with the same care as loose Lipos. When peak power is

not a critical factor, as it isn't in a TX, then opt for LiFe batteries rather than 

Lipo as these are reported to be more robust.