10
Power relay control.
PowerMon-5S can drive a power relay (either mechanical or solid-state) using the
RELAY output. When active (relay turned on), the RELAY terminal is internally connected to BATT- by the device.
The relay should be connected between the power supply (battery positive, typically) and the RELAY terminal.
The low/high voltage disconnect, temperature disconnect, over-current disconnect, and generator
control functions require the use of a relay / SSR (Solid State Relay).
Low voltage disconnect.
When this feature is enabled, and the battery voltage drops below a specified
threshold, the device turns the relay off, disconnecting the loads to protect the battery from over-discharge. To
disconnect the load, the voltage must be below the set threshold for a configurable amount of time. This feature
helps in situations like cranking an engine or a short high current load that causes the battery voltage to
momentarily drop. The device will re-engage the power relay a configured amount of time after the voltage
goes back above the connect threshold.
High voltage disconnect.
This function is similar to the low voltage disconnect, but as the name suggests
it will disconnect the load when the voltage goes above the disconnect threshold and will reconnect the load
when the voltage goes below the reconnect threshold. This mode can be used together with the low voltage
disconnect.
Over-current disconnect.
When this feature is enabled and the measured current increases above a
user-specified trip value, the device disconnects the load, protecting the batteries and load from over-current.
The device will re-engage the power relay a configured amount of time after the current drops below the trip
threshold.
Battery fuel gauge.
PowerMon-5S computes the battery state of charge and various statistics. This is
accomplished by using coulomb counting. Due to the complex nature of chemical batteries, small errors in
measurement and integrating current over long periods of time will introduce errors in the state-of-charge
estimation. This is normal and expected. For this reason, the device will re-synchronize its SoC counter with the
battery every time a full charge is performed. A full charge is detected based on the chemistry of the battery
but in general, it requires the voltage to be higher than a threshold while at the same time the charging current
is lower than a threshold. The battery fuel gauge will also take into consideration the Peukert effect. The next
table shows the Peukert coefficients used for various battery chemistries.
Battery Chemistry
Peukert Coefficient
Lead Acid - Flooded
1.25
Lead Acid
–
AGM
1.15
LiFePO
4
1.02
Li-Ion/LiPoly
1.02