We have had two LiPo fires at our Nationals. As Safety Officer I have investigated both... as well as being next to both when they went up! Here is some advice from those experiences.
Check your charger. There are some on the market that default to the NiMh setting if they are shut off through loss of mains or battery power. Set up your charger charging a LiPo. Disconnect the main power supply. Disconnect the LiPo and reconnect the main power supply. See what settings come up on the charger. If it is NiMh then stick a ruddy great big label on the front of the charger that says "CHECK SETTINGS" so you don't forget every time you switch on.
LiPo containers. Make sure it is one that is woven from Kevlar. Wherever possible, check to see if the stitching is Kevlar too - most aren't. In the first fire the LiPos were in a 'box' and the fire came straight out between the gaps, melted the Velcro and the cotton stitching and the box sprung open. Cue hot debris spewing everywhere across the pit tables. All the box types I investigated were like this, so my recommendation is not to use a box-type LiPo sack at all.
The problem with boxes is the direct access the fire has to the stitching and the Velcro. The fire burns the stitching and Velcro away and the box flaps fall open.
In the second fire, the LiPo was just tucked into the pouch near the top and the Velcro was not fully closed. Again the fire melted the Velcro (not difficult, it is plastic!), the flap popped open and the fire chucked its hot debris across the pit table setting fire to a body shell. In this case the fire was directed off the flap and so at least went only in one direction.
Pouches don't seem to suffer from the stitching being burnt. On most the stitching 'clamps' the Kevlar pieces to each other closing off the stitching to the fire. In the second case there was no damage to the stitching.
When using a pouch, use short (preferably flush) connectors and push the LiPo as far to the bottom of the pouch as possible. Close the flap so that the Velcro is fully home and the gap at the top is the minimum you can get it. That way if the fire starts, the route for the hot debris is as tiny as possible, and it is prevented wherever possible from getting to the Velcro and melting it leading to the flap coming open.
As for dealing with a LiPo fire, sand is the best weapon by a large margin. Do not us water - the heat will liberate oxygen from the water making things worse - and do not use either foam or water extinguishers for the same reason.
Use dry sand, preferably kiln-dried sand, in a large metal bucket. Not wet sand, that water problem again. When alerted to a fire, dump enough sand onto the fire to smother it. Don't pay any attention at all to people's kit, the table or the pouch, just dump sand onto the pouch until the hot debris stops coming out. It takes quite a bit of sand to do that!
Once the fire is out (listen, it can be heard) leave it for 10 or 15 minutes. Disconnect the LiPo by unplugging the wires from the charger or cutting them. Then put all the sand, the LiPo and the pouch back into the bucket and take it outside. We left them for a couple of hours after which they were cool and we could dig out the charred remains and put them in the bin.
Never pick up a LiPo or its sack whilst it is ablaze, and not for at least 10 to 15 minutes afterwards. If the fire is in a car on a tarmac track, leave it to burn out or dump sand on it. If it is indoors, get sand on it ASAP and plenty of it. People always come first - get away from the fire. They are not replaceable whereas kit is always replaceable.
Home storage - in a pouch. As said above, providing they are good quality batteries and they are not fully charged accidents are not a common occurrence. The ammo box is also a good idea.
I have asked the Electric Board to discuss the issue of the Velcro and the stitching with the manufacturers and am awaiting a reply. At least three buckets of sand (two in the pit area and one near the rostrum for the track) are mandatory for 12th Nationals. Foam and water extinguishers are also required in case any of the solvents or cleaners we all use cause a fire. Smoking is not allowed in the pit area!
In summary - use a pouch not a box. Put the LiPo as far to the bottom of the pouch as possible and make sure the flap is closed fully down with a minimum gap for fire to access the Velcro. If anything happens get clear and dump sand on the fire until the hot debris no longer comes out. Once out, leave for 10 to 15 minutes, then carefully put all the sand and the LiPo/sack into the bucket and cover with more sand. Leave for a couple of hours before removing the charred remains, or dump the whole bucket of sand with the bits into a metal bin for collection.
I am very sorry to hear someone got hurt and wish them a speedy recovery. If you have any questions, please ask here.
Peter Winton
Safety Officer - BRCA 12th Section
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