External Battery Module
The External Battery Module (EBM) is an accessory to extend the battery life of Plug & Sense!. The extension period may be from months to years depending on the sleep cycle and radio activity. The daily charging period is selectable among 5, 15 and 30 minutes with a selector switch and it can be combined with a solar panel to extend even more the node's battery lifetime.
Typical scenarios for this accessory are remote places where a power supply is not available or places where a solar panel is not suitable, like tunnels or cloudy environments.
Nodes using solar panel can keep using it through the External Battery Module (EBM). The EBM is connected to the solar panel connector of Plug & Sense! and the solar panel unit is connected to the solar panel connector of the EBM
Technical specifications
26 A·h high performance non-rechargeable battery
Dimensions: 122 mm x 82 mm x 85 mm (without mounting feet)
Cable length: 0.6 m (cable from EBM to Plug & Sense!)
Operating temperature range: -30 ºC to 70 ºC*
Low self-discharge rate
IP65 waterproof, polycarbonate enclosure
On/Off switch
Operating mode selector (3 different modes)
Solar panel voltage: up to 18 V
2 different solar panel options available
*Temporary extreme temperatures are supported. Regular recommended usage: -20, +60 ºC.
The EBM is specially designed to minimize its power consumption and maximizing its efficiency and the energy delivered to the node. This way, the internal electronic is in an ultra-low power state most of the time. The pictures below show a general view of the EBM main parts.
As shown above, the EBM has 2 sockets: One for the solar panel and one for the Plug & Sense! node. An extension cord will be used to connect the EBM and the node.
A solar panel can be attached to the solar panel connector, providing extra energy to the Plug & Sense! and extending the EBM life. Furthermore, if the charging period occurs while the solar panel is providing energy, the EBM will only provide the necessary current to fulfill the demand of the Plug & Sense! node. If the solar panel is able to provide all the current demand, the EBM will not contribute during the charging process. This way, the system does not waste energy from the solar panel and, at the same time, it enlarges the EBM battery lifetime.
Finally, the EBM is compatible with all the Plug & Sense! product range, but it is not compatible with other Libelium products like Meshlium, Smart Parking or MySignals.
Operating modes
The EBM is designed to charge a Plug & Sense! node once per day during a preprogrammed period of time.
There is a latch button to turn on and off the EBM. This button also includes a red LED to show the user when the device has started working. It will blink only a couple of times when the device is switched on, to avoid unnecessary current consumption through it. When the device is on, the button will look like in the picture below.
Due to the nature of the EBM battery, its level cannot be monitored. If the LED does not blink when the button is pressed, the EBM battery could be empty. On the other hand, when the button is off, the battery is physically disconnected from any circuitry and there is no power consumption from the battery, even if there is a solar panel present. Finally, the LED will not be on during the charging period for efficiency purposes.
The External Battery Module has 3 operating modes. In order to select them, there is a 3-position rotative selector switch.
The operating mode determines the daily time that the system will be charging a node:
Position 1 will set the charging time to 5 minutes per day
Position 2 will set the charging time to 15 minutes per day
Position 3 will set the charging time to 30 minutes per day
During the charging period, the Plug & Sense! node will be recharged at the maximum charging current, which is 300 mA. The operating mode must be selected before turning on the EBM. The selector will be read just after turning on the device and the button LED will blink accordingly to the selected mode (one blink for position 1, 2 blinks for position 2 and so on). If the mode needs to be changed, it is necessary to turn off the EBM first, otherwise moving the selector will not have any effect. Moreover, It has to be taken into account that temperature variations might induce small time drifts due to the tolerance of the internal electronic components.
If the Plug & Sense! charging current needs to be monitored, please use the example power 06: battery recharging. The current flow trough the Plug & Sense! solar panel connector will be printed on screen. Besides, take into account that the EBM will start the selected charging period 5 minutes after turning it on.
As can be inferred from the previous lines, the EBM battery life will be larger in position 1 than in position 3. To estimate the battery life, consider that the maximum allowed charging current through the Plug & Sense! solar panel connector is 300 mA (it becomes smaller when the Plug & Sense! battery is near to 100%). Moreover, take into account that environmental conditions like temperature or the battery self-discharge may affect also to the EBM lifetime.
Finally, when the EBM battery discharges completely, the EBM will bypass the current from the solar panel directly to the Plug & Sense! unit.
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