Charge Control; State Of Charge (Soc) Measurement; Cell Balancing - Valence RT User Manual

negative voltage) across the terminals. No current will flow. However, the battery will accept
charge.
When the battery has a GREEN LED status indication, it can be discharged in a normal manner.
If the LED is YELLOW, the battery is either nearing a thermal limit or the capacity is less than
20% SOC. If any battery has a RED LED status indication, it will stop discharging. A battery will
also stop discharging once it has exhausted capacity. In this case, it will return to normal
(GREEN LED) once the cell voltage increases over 2.7V during charge.

7.2 Charge Control

When the modules are charged to the point where any single cell block reaches its maximum
value, 3.9V, the battery will prohibit further charging by opening up an internal disconnect.
When the voltage of the cell returns to a value less than 3.7V, its internal disconnects will
automatically reset.

7.3 State Of Charge (SOC) Measurement

Individual cell voltage and charge/discharge current will be used to measure the state-of-charge
(SOC) of the battery. The estimated capacity used for the calculations will be adjusted to meet
the capacity of the lowest capacity cell bank when the pack is fully cycled. The state-of-charge
will be adjusted for normal
self-discharge of the battery when the unit is not on charge.
SOC Accuracy is greater than 90%.
NOTE: Lead acid state-of-charge meters should not be used with U-Charge
systems from Valence Technology. They will not be accurate.

7.4 Cell Balancing

Battery cell variability and environmental conditions can cause slight state-of-charge imbalances
between cells. This imbalance can cause reduced capacity of traditional battery systems. To
minimize potential capacity issues, the battery automatically performs adjustments to balance
the state-of charge in the cells during the top of charge.
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Phone (888) VALENCE or +1 (512) 527-2900, Fax +1 (512) 527-2910
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Phone +44(0) 28 9084 5400, Fax +44(0)28 9083 8912
Email: sales@valence.com, Web site: www.valence.com
Performance may vary depending on, but not limited to cell usage and application.
If cell is used outside specifications, performance will diminish. All specifications
are subject to change without notice. All information provided herein is believed,
but not guaranteed, to be current and accurate. Copyright © 2005-2008 Valence
Technology, Inc.
®
power
Revision Date October 2008