Ideally our batteries should be charged in 3 stages:
This is similar to many intelligent lead acid chargers which commonly have 14.4V as an acceptable steady voltage in equalization phase.
Valence does not specify a charger. However the charger you use should have a maximum output to match the maximum charge voltage of the battery system with the three stages as outlined in Q1, i.e. constant current C/2 maximum, constant voltage then float charge.
Additionally our BMS can help control many different brands of chargers for optimum charging and balancing (See Q2 & Q 4 also.)
Due to the way the batteries are constructed from many internal cell blocks it is very important that during charging these cell blocks are allowed to balance (i.e. reach the same charge level), otherwise the total battery output performance would be limited by the cell block which is lowest charge state. This balancing should be performed as often as possible to keep the overall capacity optimum and ensure that all batteries within a pack are contributing equally to the total output.
This period between balancing can be extended depending on the application but the result will be that available capacity would be reduced and when balancing is finally performed it will take much longer to bring all cell blocks to same charge level. (see Q18 also).
Any orientation is possible as there is no free electrolyte inside, however we recommend the terminals are upright, particularly when sideways mounted.
A Battery Management System is necessary for control and protection during discharge and charging, it is essential for use with U-Charge XP modules (but not for RT Versions which can use simpler BDI bar graph type module). The BMS provides CAN bus communication of battery status ‘state of charge’ and alarms etc. but may also be used without CAN bus interface with just basic analog inputs and outputs for simpler systems. Valence provides two hardware versions to match the system voltage required.
We recommend that the batteries are installed in a location where direct application of water is avoided and certainly there should be no pooling of water on any surface of the battery. A covered tray is ideal but it does do not need to be environmentally sealed. Tray designs should incorporate measures to prevent direct exposure to large volumes of water and also incorporate drainage if the worst should happen.
As with all batteries having exposed terminals it is strongly advisable where salt spray is a possibility that it should not be able build up around electrical connections. In all situations a periodic visual inspection is recommended to check the integrity of the tray.
The present generation has been developed to match existing automotive industry BCI form factors and capacities, as well as being scalable to allow larger packs to be built up into complex physical dimensions.
Yes Valence already manufactures “custom” packs to suit the needs of personal transportation solutions but obviously this approach will depend on the overall business case. Contact Valence to get more details on these custom solutions?
Yes our batteries are already providing motive power in hybrid and electric vehicles and are approved to standards IEC61960, DIN VG96 924.
They should be restrained from movement in all 3 axes without excessive single point pressure on the reinforced plastic case.
This can be accomplished by fitting in a tray base with high density foam and insulated securing bar across the top to stop any vertical movement. It is advisable to keep terminals and communication terminals accessible for periodic inspection and in some applications allow space for cooling airflow. (See Q9)
This really depends on the environment and the typical energy usage profile. A small capacity pack which is being “worked hard” will generate more heat than larger capacity pack. In operation the batteries should be kept between -10 & +50degrees Celsius. (Ask Valence for advice at Valence Support Team )
A single RT module can be used without BDI (as it will internally balance cell blocks itself), however when using up to 4 modules in series a BDI is essential to balance the charge currents.
The Lithium phosphate chemistry does not exhibit any ‘memory’ effect in the way other types of batteries do, so remain usable across 100% of capacity. However the batteries must remain above minimum voltage (>2.3V per cell block) to protect the cells from possible reverse currents, once the battery reaches this minimum level it should not be left at this level and must be recovered up to its normal operational voltage as soon as possible.
The fundamental safety rule is that batteries at different states of charge should not be connected together. Electrical isolation of batteries at different states of charge must be maintained until all modules in the pack (including the new replacement) are fully charged. For help to achieve this it is strongly advisable to contact Applications Engineering team for support Valence Support Team.
Each module is programmed with individual ID number e.g. 001 and the BMS can address directly with each module on a shared RS485 communication channel.
This is an extra option already installed and operational on some large electric vehicle systems with parallel battery systems. It gives the reassurance that in the event of single point fault the remaining portion of the battery pack will continue to provide energy. It’s enabled through extra control and switching wiring and also involves an additional level of management control supervision which Valence have developed and can support.
128 is the present limit due to the addressing limitation on the shared RS485 communication link. (Note: there are hardware limitations on the system pack voltage and current limitations exist due to external wiring which need to be observed)
The normal BMS CAN interface is SAE J1939 CAN 2.0B standard 11bit message addressing with rate options for 125/250/ 500Kbits. Also extra interface hardware can extend the message addressing to 29bit to accommodate the host controller in certain applications.
The modular sizing and programmable options on the BMS with our on site Valence Technical support services allow faster integration than many competitors.
Additionally the XP-Monitoring & Diagnostic kits provide development engineers useful tools to be able to quickly and easily analyze the system performance and thermal characteristics to fine tune the installation.
In order to give you a more comprehensive answer we need to better understand your system needs. Contact us and we will work with you to give you a comprehensive overview of what can be achieved.
The complex SOC algorithm has been developed by Valence to give a prediction of the remaining capacity based on many real time measurements inside each of the modules. The accuracy of the SOC is very good but its linearity benefits from regular full charge & cell balancing and also from periodic discharge below approx 16% where a re-calibration is performed on each module. (See also Q2).
Generally in vehicle applications we advise the period of this re-calibration can be determined during initial trials so that it can be incorporated within a timeframe alongside other service intervals.
The important factors are to match;
Yes there is a small self discharge with XP modules but they can be stored for up to 1 year without needing to be re-charged. Caution: the self discharge is accelerated with higher storage temperature (>45degrees C).
The RT version modules have internal protection electronics which consume current and if stored need to be put into ‘shelf mode’ for reduced current drain.
In all situations it is advisable to check the condition and state of charge every month to ensure that batteries are not over discharged.
Torque setting depends on the module type as follows: U1= 12.4 Nm maximum (110 in-lbs ). Retorque on occasion to 9.6 Nm (85 in-lbs) U24, U27, UEV= 18 Nm maximum (160 in-lbs). Retorque on occasion to 14.1 Nm (125 in-lbs).
At higher temperature the capacity will be reduced and constant exposure will cause increasing capacity fade. At lower temperature the impedance will be higher reducing efficiency of charging and discharging.
The BMS will protect the system from short term over temperature operations but the installation must keep the batteries within the recommended temperature for operation -10 to +50 degrees C at all times. Room temperature is the optimum for both long life and performance.
If your application is designed to work in extreme conditions please contact one of our application engineering team for advise. Valence Support Team