Battery Safety
Lithium-Polymer – (Li Po) is currently the most popular
battery used in RC aircraft. The amount of energy they store is
impressive. If handled correctly, they will serve you well over 300
recharge cycles.
Most batteries are hazardous. Lithium Polymer (Li Po) batteries
are especially dangerous when abused. They are susceptible to heat,
so never leave a Li Po battery in direct sunlight for extended
periods of time. If you take an arsenal of batteries to the flying
field, take them out of your car, or you may find yourself walking
home after the car roast.
Once you have witnessed the flammable and explosive potential of
these batteries, you will gain a new level of respect for this little
power plant.
http://www.youtube.com/watch?v=-DcpANRFrI4&feature=related
http://www.youtube.com/watch?v=37w8nzgcr9c&feature=related
Purchase a set of LiPo bags, and keep them in the bags when they
are not in the helicopter. Especially when charging the battery. They
are most susceptible explosion during re-charging.
Designate a charging area (preferably outside). Make sure there is
nothing flammable in the charging area. If you do not have a Li-Po
bag, get a ceramic flower pot that has a ceramic lid. Dangle the
battery inside the flower pot, and gently lower the ceramic lid over
the opening so that you do not damage the battery wires (you can use
a ceramic bit to gut notches in the lid for the wires).
Never use a puffed up battery pack. It is puffed up because it was
over-discharged or over-recharged resulting in over heating and the
laminates begin to separate. Overheating usually occurs because it
was used near or below it's 3.1v per cell minimum voltage rating, or
it was over charged beyond 4.2v per cell maximum voltage rating or
used in an application that called for a higher C (current) rating
than the battery could handle. Once a battery has “puffed”,
the internal damage has been done. The battery may shrink back to its
original size, but it is no longer safe to use because the internal
laminates have become damaged and pose a serious out of the blue fire
at anytime. Chemical reaction takes time, but once it is on its way,
it can quickly escalate into fully functional chemical fire.
Time your flights. Most modern radios have built in timers just
for this purpose. The objective is to never get the battery drained
to the point where the ESC starts to shut down. Less is better. It is
better to fly for 5 minutes at a time, and make the battery last for
years, rather than over fly it, and kill it in a couple months (or
less).
*Note – your throttle curve directly contributes to the
amount of time you can fly. Higher speed, means the battery is
draining faster.
Balance your battery at least every 5 discharges. Modern chargers
use the main battery cables to supply recharge power, and a connector
with 4 or more wires (called the balance plug) to monitor the
balancing progress. If one cell is less than the others, the charger
stops charging through the main cables, and applies charge (through
the balance plug) to the single cell needing to catch up until it is
even with the others, then full charging resumes until one of the
cells again drop below the others. Lower cost battery chargers
either only use the balance plug to charge the battery, or only the
main cables. If you have a low end battery charger, do yourself a big
favor and buy a real LiPo battery charger (I highly recommend the
Thunder AC6 charger).
If you crash the helicopter. Remove the battery and set it aside
for 15 minutes. If it does not explode or puff up in that amount of
time, you can return it to service. Continue to monitor the battery
closely the next time you charge it – oddly, you can often more
safely discharge a battery than recharge it.
Never dispose of a LiPo battery with the common waste. Soak it in
a salt water solution for 7 days, then it can be safely disposed of.
Never leave a charging battery unattended. I know of one story
where the battery was left unattended for 15 minutes in the garage
while the owner went into the house to get something. The battery
burst into flames, and ignited other flammable containers in the
garage, and lost the entire house. Chemical fires are difficult to
put out.
Never charge a hot battery. It’s tempting to plug it in
again right after you flew it, but give it a rest until it’s
cooled to room temperature. Do not become impatient, wait for it to
cool before starting a recharge. Alternate flying batteries per
flying session. Number or tag your batteries, and use them and charge
them in the same order.
Batteries should not get hot while charging. If they do,
immediately unplug the charger. Do not move them until they return
to room temperature. If you see the battery starting to puff up or
smoke, it is an imminent fire.
A fully charged LiPo battery holds 4.2 volts per cell. If you are
using a 3S LiPo, it will have a full charge of 12.6 volts.
*Note – Buy a good battery charger. The inexpensive chargers
that come with RTF models are inadequate for this hobby. A good
balance charger has built in safety features, and superior battery
monitoring and charging capabilities. Your batteries will last for
hundreds of cycles when using a good charger. It will easily pay for
itself. These better chargers can also safely charge your
larger/”higher C” batteries faster than more conservative
chargers.
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