The following is a review of the RC Models Distribution Lipo Voltage Guard,
Manufactured by CSM Design Consultancy Ltd.
The unit is a piezo sounder style voltage alarm that is fully programmable for different cell configurations and voltage settings. The unit consists of the piezo sounder and a small servo style lead for programming the lipo voltage guard.
Initially some pictures of the unit .....
The voltage guard is easily installed. The red and black wires should be
directly soldered to the battery (lipo) connector leads on your ESC, effectively
wiring the voltage guard in parallel to the lipo. This effectively puts
the voltage guard right on the source cables for the lipo when installed
in the T-Rex, enabling accurate measuring of the lipo voltage level during
flight. The lipo guard is accurate to within 1% of the set voltage. Here
are some manufacturer specifications :
Operating Voltage
5V - 45V
Minimum Threshold
5V (2 cells, 2.5V/cell)
Maximum Threshold
34V (10 cells, 3.4V/cell)
Precision
1% or better
Current draw
35mz max. during alarm, <10ma otherwise
Weight
4g
Size
28mm x 20mm x 10mm
The lipo guard is secured to the model using servo tape. Manufacturer defaults
are for 3 cells and 3.0V per cell alarm threshold. The timed minimum hold
feature is also set as default.
At startup the lipo guard beeps four times to show it is active, it will
not beep again unless your lipo hits the set threshold voltage. When this
happens the voltage guard beeps at approx. 1 second intervals with single
beeps. If you ignore this then when the voltage goes more than 0.1V below
your voltage threshold then the alarm will beep twice every second. Ignore
this and you go to three beeps per second at more than 0.2V below the set
threshold.
In the T-Rex I found my packs were starting to sag on or around when the
factory default sounds the alarm. Ideally I wanted to avoid pack sag and
land before this happens. I reprogrammed the device for 3.2V per cell as
the threshold, I now get ample warning before the pack sags.
The voltage guard can be programmed for anything from 1 to 10 cells and
within a voltage range of 2.5V/cell to 3.4V/cell for the alarm setting.
Programming is via the supplied cable which plugs from the Lipo Voltage
Guard to your receiver (throttle channel). Programming is done by listening
to beep codes and putting the throttle stick in the appropriate place to
change that setting.
Below are pictures of the final mounting of the sounder, well away from
other electrical radio equipment.
In flight the Lipo Voltage Guard works perfectly, sounding tones at around exactly the point I would expect, I've taken to not timing my flights now as the sounder lets me know before I hit pack sag or ESC power reduction mode.
Lastly the Lipo Voltage Guard has two settings, timed minimum hold and
indefinite minimum hold.
Timed minimum hold sounds the alarm for twenty seconds on hitting the pre-programmed
voltage, after which it changes to the present voltage. Indefinite Minimum
hold sounds the alarm when the pack reaches it's lowest voltage since startup.
Overall Conclusion
A very cheap and worthwhile addition to my T-Rex. It removes the guesswork
from pack flight times and allows careful monitoring of pack voltage levels.
Hopefully this will also increase the longevity of my packs as I am never
likely to over discharge by mistake, not that I do this but it's good to
have the Lipo Voltage Guard there as a safety net. This is particularly
useful for flights that are very stop start (difficult to time) rather
than continual flying where a stop watch can work just as well.