LISA - Lithium battery Saver
LISA is specially designed for use with
electronic speed controllers; ESCs; that are not designed for today's lithium
battery.
Most of the ESCs for
brushed motor in use today are not designed for lithium battery, therefore, we
often get swollen lithium battery pack after 1 or 2 flights. It is the
result of over-discharging the battery and; of course; the battery becomes a
scrap. It is not just about loosing your money, safety is more important.
A swollen battery pack can explode and injure people nearby. This is the
reason for using LISA in your airplane.
| Specifications |
mm (in) |
| Length |
30 (1.2) |
| Width |
14 (0.6) |
| Weight (without wire) |
2.8g (0.1oz) |
LISA can handle 2 (7.4V), 3 (11.1V)
or 4 (14.8V) cells lithium battery pack. It measures the voltage across
the power leads to determine the number of cells, therefore, in order for LISA
to function correctly, always use freshly charged battery to begin a
flight.
LISA not only measures voltage of the battery
pack but also the output voltage of ESC. An ESC supplies +5V to the
onboard electronics through the receiver connection wire, this +5V must be
fairly stable in order for the receiver and servos to function properly.
However, during development, I found that some cheap ESCs cannot maintain the
output voltage. In 1 of the samples, the output voltage
starts to drop as soon as the battery voltage is dropped below 7V (A 2-cell
lithium battery pack). And, the output voltage is dropped to 3.1V when
battery voltage is 6.5V, the onboard electronics may not function properly at
such low voltage. Therefore, we decided to add a feature in LISA to
monitor the ESC's output voltage; where LISA will stop the motor when output
voltage is dropped below 4.5V.
|
2-cell (7.4V) |
3-cell (11.1V) |
4-cell (14.8) |
Description |
| Soft cut voltage (Note 1) |
6.0V |
9.0V |
12.0V |
Throttle is limited to 80% |
| Hard cut voltage (Note 1,2) |
5.4V |
8.1V |
10.8V |
Motor stopped |
Note 1: ESC can resume its function as soon as voltage is recovered
Note 2: Hard cut also occurs when output voltage of ESC is dropped below 4.5V |
Circuit Diagram
|
