| THE USUAL ADVICE
regarding charging NiCad batteries is: "If in doubt, charge the
battery anyway". This is good advice as far as it goes, for clearly
if the battery is flat while the model is in use, all control will
be lost. It is not, however, the best way to care for your
battery.
It's a gas!
If a
NiCad battery is charged further after it reaches full charge, the
electricity passing through the cells is dissipated as heat and by
the generation of gases.  Many years ago, when sealed button cell (DEAC)
batteries were used, the cells would swell and burst. With modern
vented cells, the gases escape to cause a more insidious problem.
Many of you will have heard of 'Black Wire Corrosion'. This is
caused by the overcharge gases from the NiCad passing along the
wires connecting the battery to the receiver. It is not only the
wires which corrode, as the connectors between the battery and
switch harness, the switch contacts and the contacts between the
harness and the receiver connection pins all suffer. In most cases,
when a model ceases to respond to the transmitted signal and crashes
and when the model is recovered everything is working perfectly, the
problem is not low range as is often suspected, but corrosion of the
receiver battery pins. The contact is remade by the scraping action
of the connector as it is disturbed by the crash. The contact will
usually remain good for a few weeks and then fail again for the same
reason. The fault can be easily confirmed by checking the receiver
contact pins for the black corrosion. If this happens to you, we
recommend that you clean the receiver connector pins and
replace |
| Charging using an approved JR
overnight charger and discharging after use is our preferred
way of keeping r/c packs in tip-top condition
|
 |
| the switch harness and battery pack wire with
new.
Discharging in
series
When fully
charged, a NiCad cell reaches approximately 1.4 volts. During
discharge, the voltage falls rapidly to about 1.2 volts and
then slowly to about 1 volt. After 1 volt is reached, the
voltage falls rapidly to zero. It is quite safe to discharge a
single NiCad cell to zero volts and no damage will be caused.
When NiCad cells are used in series, as in receiver and
transmitter packs, the situation is quite different. With
quality NiCad batteries, the capacity of all cells in a pack
are matched to each other but even so, upon discharge,
inevitably one of the cells will become discharged before the
others. If discharge is continued beyond this point, the
remaining cells will force electricity through the discharged
cell in the reverse direction, causing irreparable damage to
the cell. This is the reason why transmitter and receiver
packs should never be discharged by leaving the system
switched on unattended. In practice, it is safe to discharge
down to 1 volt per cell (4 volts for the receiver pack and 8
volts for |
the transmitter pack) as at that level it is most
unlikely that any single cell will be at zero volts. We find
that the most convenient way to discharge a partially used
NiCad is with the discharge part of a battery cycler.
Storage
A NiCad battery, unlike a car battery,
will not be harmed by being stored in a discharged condition.
Our recommendation is therefore that after use, you discharge
your transmitter and receiver batteries down to 1 volt per
cell and then store them discharged. Immediately before use,
the batteries should be charged for 12 to 14 hours using the
appropriate overnight charger. After the modelling session,
whether or not the batteries have been used, they should once
again be discharged to 1 volt per cell.
If you adhere to this procedure,
you will always have the full battery capacity available
without the danger of overcharge. As an added bonus, any
deviation from the normal time of discharge will provide an
early indication of a
problem. | |
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