There are many thoughts by many people on Lipo safety, listed below are the ones which I consider to be the most important.
Please let me know if you have any other thoughts/ideas which can be noted and then passed around to club members.
I gather from most people that Lipos when treated correctly are as safe as any other battery, otherwise we would have umpteen model shops burned to the ground. Most problems seem to occur while charging and this can happen for a number of reasons.
Never charge a damaged Lipo caused either through crash damage or other reasons.
Best and safest charge rate is 1C which is 1 x the capacity of the battery. Example: a 3000mAh Lipo would be charged at 3 amps. Some Lipos advertise charge rates of up to 5C and while this may be so it doesn’t do the Lipo any good long term.
The balance lead on a Lipo plays a very important part in the charging process and should be connected every time. The reason for this, on a normal charge the individual cell voltages are being monitored so no cell should exceed 4.2 volts and the charging process should stop even if some cells haven’t reached the 4.2 limit.
If the balance lead is not connected, say for example on a 3 cell Lipo, the charger is looking for a total finished voltage of 12.6 and it doesn’t know how this value is made up. One cell could be 4 volts, another 5 volts and the third cell 3.6 volts, the danger being the cell at 5 volts. With a few chargings like this the overcharged cell is likely to start degrading and swelling up.
I have been told that 90% of heat generated in a Lipo happens in the last 10% of usage causing the Lipo to swell and I consider this to be true through my own experiences of over discharging Lipos. I now adopt Bill White’s practice of trying to leave 20% capacity in the Lipo at the end of a flight. Bill is an F3A competition flyer and generally charges and discharges his Lipos at least 800 times with no adverse affects.
The charger and Lipo should be sat on a heat proof surface with the Lipo in a charge sack or bag which will help to limit any damage.
All chargers vary in their set up but most have a few safety features that when activated can stop a potential disaster.
The timer can be set to knock off after so many minutes charging, after a couple of charges you should see how long it takes to charge a certain pack and can adjust the timer accordingly.
The charge limiter can be set to the capacity of the Lipo and again will stop charging when this has been reached.
Remember that if a Lipo starts hissing or bubbling either during or just after charging it is likely to catch fire and once started will not stop until used up. The heat is very intense as it is a chemical fire which produces its own oxygen so it is best to try and contain it rather than try to move the Lipo while burning.
This leaflet is best read in conjunction with the BMFA’s guide to Lipo safety.