9th July 2017
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.
BMFA booklet outlining the safe and effective use of lithium polymer batteries in model flying.
Essential reading for everyone who uses LiPo batteries. Click on the picture below to read this 'Lithium Polymer Battery Safety' booklet recently issued by the BMFA.
18th July 2014
Protect your transmitter from the sun
Now that summer and the sun, when it appears, is at its strongest care must be taken to shield our computerised transmitters from sustained bright sunlight. Recently one of my flying friends damaged a display screen on his transmitter after it was left unprotected in bright sunlight for an hour or so. The transmitter still works but needs a replacement screen. This brought back memories of an incident a few years ago when a Tx was left in the back of an estate car with the boot lid up in bright sunlight on a hot mid-summers day. When he went to fly the only thing operational was the power on LED. No fault was found during subsequent fault investigations and the conclusion was that the temperature of the Tx was outside its operation temperature limits. So take care and shield your transmitter from the sun.
What is defined as a large model?
Click on the link below to download the article
The Falco Project
John C'ill describes design and initial build of his Falco Project
Click on the link below to download the article