MPBA GUIDELINES ON USE
OF LIPO BATTERIES
Lipo batteries are now used
by a very significant number of model boaters and they must be treated
differently to more conventional rechargeable batteries.
The most useful aspects of
their operation is the very low self-discharge rate, which can be as low as one
or two percent per month. This gives them the extremely useful property of being
able to be charged when you come home from boating and still be fresh and ready
to use even several weeks later.
Anyone who has forgotten to
put their batteries on charge the night before a boating session will appreciate
However, they are different
to conventional cells and probably the most important aspect of these batteries
from a safety point of view are the consequences of overcharging, over
discharging and crash damage.
The individual Li-Po cells
are nominally 3.7 volts with a maximum fully charged rating of 4.23 volts and a
minimum safe discharged rating of 3 volts.
If you over discharge the
battery too much below 3 volts per cell you will almost certainly damage it
permanently and it will not then accept a re-charge. NEVER leave a Li-Po battery
connected to something that will allow even the slightest discharge, as the
battery will be effectively destroyed in a few hours.
If you charge your battery
beyond the 4.23 volt per cell limit, you risk damaging the battery and also have
the possibility of a thermal runaway, resulting in a battery fire. You MUST use
a dedicated Li-Po charger and, if your charger is not automatic, you MUST make
sure that the voltage control on the charger is set correctly for the number of
cells in the battery you are charging.
Most Li-Po cells and
chargers have a cell balancing facility and the use of this will help keep the
cells working efficiently and safely. In fact, we would not recommend the
purchase of a Li-Po charger that didn’t have this facility available.
You must also use a speed
controller (ESC) that is designed for use with Li-Pos and will not allow them to
Other precautions should
also be taken when charging.
Do not charge at more than
1c unless specifically authorized by the pack vender
Never charge batteries in a
model, always remove them from the model.
Charge on a safe surface in
a position where a battery flare cannot ignite other items. A Li-Po burn only
lasts a few seconds so it is not a long-term fire source but it is extremely hot
and will easily ignite other flammable items that are in close proximity.
Dedicated ‘charging bags’ are also available that will contain any Li-Po
flare if used correctly.
Damaged cells are usually
very easy to spot as they ‘balloon’ out.
The cells are generally
‘softer’ than the traditional Ni-Cd types and are much more susceptible to
crash damage. Any visible damage to the cell should be treated with suspicion.
Any cell that is
‘ballooned’ by charge/discharge problems or by crash damage should be
Any cells you wish to
discard must be made safe. The commonest recommended method of doing this with a
damaged cell is to discharge the cell electrically and then submerge it in
strong salt water for at least 12 hours. After this the cell is inert and may be
disposed of at your local recycling site. For more guidance on the subject you
should consult the Internet for the latest information on cell disposal.
Always read the
manufacturer’s information on the cells you are using, as this will give you
the information on maximum charge and discharge rates.
Checking lipo volts in
4.23v = 100%
4.03v = 76%
3.86v = 52%
3.83v = 42% = typically
used as a storage charge Recommended
3.80v = 30%
3.75v = 11%
3.70v = 0 %
These are resting voltages
–not under load voltages
All models must have a kill
switch for the radio control equipment(excluding
scale craft) this is operated from the outside of the model (loop system
is recommend) in case of emergency the competitor, start assistant, recovery
boat or any other person can interrupt the power supply between the motor and
Recommended for the race
platform or pits area
A first aid kit, fire
extinguisher, fire blanket and a bucket of dry sand has to be present.
It is up to the officer of
the day to see where these are allocated on the day.
Lithium Metal fires
Lithium Metal fires must be
tackled with a specialist lithium extinguisher, commonly sold as a
L2 extinguisher. A sodium chloride extinguisher is not suitable for use
on a lithium metal fire. Cells/batteries not containing Lithium as a pure metal
do not require a L2 extinguisher.
If any fire gets out of
hand call 999
MPBA members are expected
to operate lipo cells in a safe and responsible manner.
Batteries shall be securely
fixed in the boat.
Do not mix batteries from
Please make sure that all other terminals apart from the one you are working on
are covered with an insulating material to avoid the possibility of a short
circuit. On completion of
alterations please ensure that all connectors are insulated and that all bare
cell terminals are covered with polyimide tape or another suitable heatproof
material ( fibre glass tape is also suitable) this will ensure that there will
not be a short circuit from any wires including balance leads.
measures should only be carried out by competent people. If in any doubt as to
your own ability you should take advice from someone that has the required
balance leads break away from a cell tag due to fatigue. The cell connection
therefore has to be repaired or the battery thrown away. The latter is not an
economic solution so it will be necessary to take the above precautions to
re-solder the wire.
Review in 12 months