Wired Mowers: Mower battery dies with error "Empty Battery" near fence/barrier/opening/dotGate
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    • Wired Mowers: Mower battery dies with error "Empty Battery" near fence/barrier/opening/dotGate


    One of the most needed solutions for a robotic lawn mower is the capability to autonomously let the mower move between front and back yard, when the two areas are separated by a fence. There are many ways to achieve this - One can have an opening in the fence, or a solution such as our dotGate that enables the mower to move while keeping the opening closed at other times may be used. 

    PROBLEM:

    The Automower is expected to follow the guide wire and charge itself when its battery is low. However, we have seen that sometimes in such a set up, the mower may just fail to do so and report an error, empty battery - typically in front of a fence, or barrier.

     

    HOW AUTOMOWER FINDS IT WAY BACK:

    Before we discuss the most probably solution, lets understand how the mower is expected to react when its battery is low. When the charge level in the battery has dropped to 1,000 mAh or the voltage in the battery has dropped to 17.5 volts, the robotic lawnmower shuts down the blade motor and starts searching for the charging station.

    Automower can be set to search for the charging station in one or more of 3 different ways: Irregular, Follow boundary home and Follow guide home. The Automower always starts a search for the charging station using the Irregular method, on the condition that the delay times for the boundary wire or any of the guide wires are not set to 0 minutes. Irregular searching means that the Automower runs in an irregular pattern until it encounters the F field near the charging station. The strength of the F signal, which is required for the mower to react, is set in the Charging station range setting. If a guide wire is installed and the delay time for this wire has elapsed, the Automower will start to search for and follow it to the charging station. If the delay time for the boundary wire also elapses before the Automower has found the charging station, the mower will also start searching for the boundary wire. If the mower then finds and follows the boundary wire, it keeps going until it has found the charging station or crosses the guide wire. If it crosses the guide wire, the robotic lawnmower will follow it instead to the charging station.

    When the mower follows the boundary wire or a guide wire, it travels a distance into the F field before the F and N signals direct it correctly into the charging station. If the boundary wire is laid around an island, the Automower follows the loop 2 times around the island before it leaves it and travels on to encounter the boundary wire at another point.

     

    PROBABLE CAUSE:

    Now that we understand the behavior of the mower when its battery is low, it is very easy to see why sometimes this error can occur. The issue mostly can be due to the way the charging base of the mower is installed, with respect to the fence/barrier such that the mower is expected to mow on both sides of the barrier. Lets take the image below as an typical scenario.

     

    The image above depicts a typical scenario where the mower may not be able to follow the guide and throw an "Empty Battery" error close to the fence as shown above. This could be caused because the mower likely dropped below the threshold of 1000 mAh around the area where the mower is also able to detect the Far field signal from the charging base, but is located on the opposite side of the barrier (fence in the example). Or the mower came across this area first, before crossing any of the guide wires, while searching for its charging base. Now because the mower gives the signal from charging base higher priority as per its search mechanism, it starts moving in the direction of the signal, but constantly faces the barrier and bounces back, only to get stuck in the loop of moving towards the charger signal and then bouncing back from the fence. This loop eventually causes the mower to run out of battery and throw the error "Empty Battery".

     

    SOLUTION: 

    The solution to this problem is very simple. Ideally, one should avoid installing the charging base close to a barrier, across which grass is expected to be mowed. The charging base should be installed at least 25-30 feet away from such barriers. But if that is not feasible due to availability of power and other limitations, then the problem can be resolved quite easily by changing the transmitting power of the far field signal on the charging base. The power is set to "MAX" by default and can be changed to "MIN" or "AVG" (depending on proximity of charging base to the barrier). This setting can be found in the Automower Connect app under Settings>>Installation>>Find Charging Station. A snapshot is shown below,


    It should be noted that the guide wire installation is done efficiently whenever the charging base signal is being reduced. With non-optimal guide wire installation, the issue is expected to persist with a higher failure rate. If you have further questions, please reach us out at support@smart-dots.com.