Data Sheet

BMS10x0
10 www.roboteq.com Version 1.0 March 2, 2018
Considering balancing, the precision can be adjusted, minimizing cell voltage differences.
Take care when altering the 10 mV default value because very low precision values may
fail to satisfy the end of balancing condition.
The BMS has by default the auxiliary output switch function set to Disabled. This means
that the state of the switch does not automatically change and script may be written to
control it.
Choosing the predefined option Brake Resistor, the BMS will automatically handle the
switch implementing an “excess energy dumping” algorithm. The auxiliary output may
also be defined as a Fan or a Heater. Their functionality is also automatically handled by
the BMS.
Balancing
Balancing is the process of eliminating the voltage differences between battery cells that
is created by the different rate of charge and discharge of each cell. Every battery that con-
sists of multiple cells in series needs to be balanced for maximizing its capacity, making
all of its energy available and prolonging the battery’s life. The voltage differences between
the cells of an unbalanced battery grow in time and uneven stresses are exerted on the
cells. This phenomenon leads to more strain on the weakest cell in the chain leading the
battery to fail faster than expected.
Generally, balancing is performed during the charge cycle by enabling a low value resistor
across the cells that have higher voltage, and thus diverting the charge current to lower
voltage cell.
Balancing is activated automatically and the user does not have to know or learn any
balancing strategies for the BMS10x0 to work.
State of Charge
SoC is crucial in protecting the battery. Due to the charge and discharge behavior of the
LiOn and LiFePO chemistries, measuring the individual cell voltage is not sufficient for
specifying the state of charge of the battery. The voltage output for this type of cell shows
very small changes when charging or discharging until reaching full charge or discharge.
The state of charge is defined as a percentage of the Ah measurement taken from
the BMS10x0 versus the real Ah capacity of the pack recalculated in every full charge/
discharge cycle.
When it is first connected, the BMS10x0 considers the battery at 50% SoC, assigning the
nominal Ah/2 capacity as the energy left in the pack and the nominal max Ah capacity as
the real measured capacity. Since the pack will most probably not be at exactly 50% SoC,
the system will automatically adjust the measurements so that the actual State of Charge
of the battery is aligned with the measured SoC, providing the user with an accurate
indication.
The Ah counting is maintained during both charge and discharge cycle adapting through
time to the actual capacity limits, while the battery ages.
The SoC is calculated based on two parameters, the Coulomb Counting measurement
and the minimum and maximum cell voltages. Since the cell voltages are not an accurate
indication of State of Charge while the battery operates in the nominal state, Coulomb