Lithimon 5678

Written by Ashley Davis Sunday, 25 February 2007 00:00

Lithimon 5678

The following is a review of the Lithimon 5678 lithium battery alarm. This alarm is configurable for five through eight cells. The device has some jumpers on it which control when the alarm will sound based on a certain threshold of voltage. The highest of these is 3 V and is the setting that I chose for my testing.

Before I go any further here are some pictures of the device:

Technical Review

This lipo alarm is designed to provide both audio and visual warning when you are getting close to the end of your pack. The device also claims to extend the flight time that you can achieve from your pack. It does this using two large capacitors fitted on the device. The details of this can be found on the Dawnmist website. This review will look at the function of this device as an alarm and also look at the claims that it extends flight time.

Configuring the device is a matter of putting a jumper on the circuit board in two different places. The first jumper setting controls the voltage level that will trigger the audio and visual alarm. The second jumper controls whether the device is configured for five cells, six cells, seven cells or eight cells. As I am testing this on a T-Rex 600 I set the first voltage level at 3 V per cell and I set the number of cells at six. Having configured the device it should be wired in parallel to the speed controller on the battery connection wires.

It was whilst configuring the device that I had my first reservations. The jumper settings allow you to configure 3 V, 2.8 V or 2.6 V. In my experience allowing a lithium polymer pack to discharge below 3 V at a high amp setting is already asking for trouble. Whilst most lithium packs can withstand voltages below 3 V per cell in a helicopter situation it will only be a matter of a few seconds after this threshold is reached that you will be down to 2.6 V per cell or less. Therefore "in my opinion" by the time this alarm goes off you will already be extremely close to damaging your pack from over discharge and probably will not have enough time to land before this happens. This is especially true of Enerland cells which have a very steep discharge curve at the end of the packs capacity. Therefore I do not believe this lipo alarm would be useful when using Enerland based products (Thunder Power, FlightPower, Poly pro).

Moving on to the claims of extended flight time. The technical information on the Dawnmist website is really quite technical but having worked through it the basics are that the Lithimon increases your flight time by conserving energy in the capacitors when running at lower throttle settings. With electric helicopters the throttle setting is normally 85% or higher and in this instance I do not believe any significant extension to flight times would be achieved.

Flight Review

In order to test this device I needed to deliberately discharge my packs to 3 V per cell. In order to do this I used a kokam based pack as these cells have a much shallower discharge curve at the end of the pack capacity. Also I use a discharge protection module with my kokam packs and therefore I cannot physically damage the cells by discharging them to the point that the Lithimon alarm would trigger. In practice what happened was a very bright LED illuminated and the audio alarm sounded. According to the on-board flight log this occurred at the required 3 V per cell set on the device. The audio alarm could barely be heard above the sound of the machine. In flight (circuiting) I doubt it would be heard at all. In the hover it was barely audible. Conversely the super bright LED was very visible and serves as a much better warning than the audio alarm.

Pros

Super bright LEDs
Easy to configure

Cons

Voltage alarm can only be set at 3 V per cell maximum
Flight time extension does not apply with model helicopter throttle curves
Audio alarm is too quiet

Conclusion

The Lithimon 5678 does exactly what it says but unfortunately the settings that are available are not entirely suitable for use on an electric model helicopter. Added to this the audio alarm is far from loud enough to be heard over the noise of the running model. As a lithium battery alarm the only thing I liked was the super bright LED's. With regard to the claims of extended flight time these do not apply when running a typical throttle curve for a model helicopter. The highest voltage alarm setting of 3 V per cell is not enough. Therefore I do not recommend this device as it doesn't really provide any protection as it will not alarm early enough to allow a landing before potential pack damage occurs.

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