Li-Pol monitor - model finder

This small device was designed at beginning of my flying hobby as modeler.

I started with heli as my first model, so my first experiences was few inflated Li-Pols battery after few flights.

Then I started to look what was the reason - yes it was too low Voltage drop during flight along with big current load, this destroying battery's chemical structure, making them swollen.

In theory, save voltage for Li-Pol is 2,7V per cell (absolute minimum value) , in practice when Li-Pol is loaded and voltage drop more than 3,2V per cell, it will result inflated/swollen battery.

In fact, if higher current Amperage is loaded, then level of voltage below battery become inflated, is higher also .

So for example, when flying craft taking about 5-6A from 1200mAh 20C 3S battery, battery can fly safely to voltage level about 9V (3V/cell).

But flying craft taking 20A from the same battery, will damage this battery when voltage drop under 9,9V (3,4V/cell) , in fact danger voltage level is even higher.

- So, first function of Li-Pol monitor must have, is regulated voltage when alarm is triggered on.

Default is 9,6V for 3S battery for alarm. For alarm's voltage regulation is small potentiometer on board. In models taking less current like 4-6A alarm trigger voltage can be quite low ex. 9,2V (for 3S pack). In model when current is about 15-20A alarm should be about 9.8-10V to prevent battery and keep battery in good condition for long time.

When voltage is measured is also filtered, so alarm is not triggered at moment when voltage momentary drop, drop voltage must be low for some seconds to confirm low state. This prevent of false alarm on, when we rapidly open throttle stick, flying heli or quadro.

To be sure, that pilot will land when alarm is on, the noise must be very annoying and such was made.

Hearing alarm, no one will think "I will land after few minutes", most are landing immediately because of this noise.

Turning of alarm if once triggered, is possible only by remove power from Li-Pol monitor.

- Another useful function is model finder. Is possible to preprogram the time when Li-Pol monitor will start to noising independently of voltage value. First it was my theoretical advantage and I never supposed to be a much useful, however I implemented this functionality into device.

At one day of my recreation flying, my plane fell down far away from place I stand. I completely lost the point when plane fall inside a field of corn-grass-bush high for 1,5 meter. Well, I was trying to find my plane, during my walk around at field, I heard alarm of Li-Pol monitor (that time alarm), only thanks for that I got my plane back, surprisingly plane was about 50 meter far from place I thought it is, 50 m is long distance.

Since that time I think that model finder ability is even better than voltage meter, without it, I had for sure lose my plane and equipment.

So model finder function is also done in device. Preprogrammed time have 15minutes intervals. So is possible to set interval as 1 , 2 , 3, ...., 15.

1 - is 15 minute to alarm start, 2 - is 30 minutes, 3 - is 3x15=45minutes ... 8x15=120min=2hours ... etc.

After power on, Li-Pol monitor will made ti-ta beep and then will beep 1, 2, 3, etc... times indicate how many intervals are set to alarm be triggered. 2 beeps means 2 x 15min = 30 minutes (default set) .

- Another Li-Pol's monitor function, is that have socket to connect 2 LED diodes imitating board lights. They flashing each once at every 3 seconds as in real plane.

But when voltage drop near the alarm value, than LEDs flashing fast all the time, indicating that alarm will be triggered very soon, so we can know the battery becoming to empty.

Best result, especially in daylight and evening/night, using blue LEDs with increased brightness, lighting angle 120degree (flat surface).

- Li-Pol monitor can not be destroyed connecting opposite black and red wire - so when accidentally connected opposite is absolutely safe for device and battery.

- For proper use, white label from buzzer should be removed to made it loud, as it is only for transport protection.

To made noise a loud, is good to place monitor inside canopy (plane body) and canopy will work as resonant box, rapidly increasing volume level.

Picture of monitor without shrink

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PROGRAMMING time alarm, this alarm is independent from Voltage level.

- To program time alarm, remember made mark on potentiometer to know where was set

- Turn potentiometer maximally to right --> , connect power .

- Monitor will noise one alarm sequence informing that is in programming mode .

Then it will start to made short beeps, one beep and one second silence, two beeps and one second space etc. to 15 beeps and again start over from one .

After we hear ex, two beeps when we remove power during one second of silence - then monitor will remember that interval is set to 2 so 2 x 15min = 30 minutes . The same for example 4 beeps - 4 x 15 = 60 minutes .

- Turn back potentiometer to place it was before, at mark you made at beginning.

As default, Li-Pol monitor is set to 9,4V and have done mark on potentiometer and blue shrink to get the right place after any potentiometer changing .

VOLTAGE alarm calibration, simple way

- Turn potentiometer maximally to left <--

- Is good to use for example new 9V battery or even better regulated power supply,

- Connect 9V battery to red and black wire, then turn potentiometer slowly to right till alarm will start to noise

- That all, Voltage alarm is calibrated to about 9,2V

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Conclusion :

Since monitor was used (now is over 4 years of experience), quantity of puffy(inflated) battery I produced in flying season rapidly decreased .

That device helping to keep long life for even cheap, not so good quality battery.

Using Li-Pol monitor in my helicopters and planes, flight time become bit shorter but I can made much more flights using the same battery.

For example, before in plane without monitor, I flow about 25minutes - ESC sometime cut, sometime not cut voltage, and battery become swollen after some of flights.

Using Li-Pol monitor, I can fly about 20-21minutes before alarm is on, so a bit shorter - ESC never cut power to engine, so always I can perform normal, controlled, not emergency landing. Battery is not swollen or puffy, still hard in touch and just passed third year of flying.

In fact I use those monitors in all my flying crafts I own.

Absolutely best and incredibly results, using monitor in Helis, Tricopter and next Quadrocopter.

Probably you guess why ? Well - you right, helicopters and multirotors, after power cut, soars with the grace of the anvil.

Monitor's alarm always give a time, to perform normal controlled landing.

Since over 4 years, owners of hundreds monitors are flying around (in Poland are my modelers friends), and users find them as very useful, especially in any kind of flying crafts.

Below are movie how prototype was tested

And principle of work, at some low voltage near of alarm level, LEDs are flashing faster (if LED are used at all), then when Voltage drop to lower level, noise alarm is triggered.

Some experimental fun with music (Airwolf) instead of alarm, unfortunate music is not loud solution, so in practice is useless on airfield, alarm must be loud and annoying.