FAQ | GTCAP

Due to the way the supercapacitor 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 super capacitor batteries within a pack are

● The complex SOC algorithm has been developed by GTCAP 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 (100% SOC) & cell balancing, and also from periodic discharge below approx. 20% where a re-calibration is performed on each module. ● 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. ● At low consumption it is important to note that the SOC of the battery can drift – a regular full charge of the batteries does help limit the drift.

Only the chargers that have a float phase can be connected permanently to supercapacitor batteries. When batteries are fully charged the charger will remain in floating mode.

● The super capacitor battery 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 (>2.5V 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. ● For the EDLC the minimum voltage per cell is defined at 2.5V. For the super capacitor batteries it is 2.5V per cell block. ● In case of deep discharge we can sometimes recover the super capacitor battery with a very low current. It is not recommended unless it is performed within our laboratory or in specific situations at the customer with GTCAP expert/engineering assistance.

● Yes, there is a small self-discharge with traction batteries but they can be stored, when full, for up to 6 months without needing to be re-charged. Caution: the self-discharge is accelerated with higher storage temperature (>45 degrees C). ● The traction batteries 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 periodically to ensure that batteries are not over discharged.

Ideally supercapacitor batteries should be charged in 3 stages: ● GTCAP suggests C/3 for a better lifespan of the batteries & 1C as maximum charging current. ● Allowed to equalize & balance cells at this level until fully charged ● Return to float charge. ● This is similar to many intelligent lead acid chargers as an acceptable steady voltage in equalization phase. ●Apart from the charge current limits which are higher for GTCAP. For the rest, the same applies to GTCAP‘s graphene supercapacitor batteries.

A Battery Management System is necessary for control and protection during discharge and charging. The BMS provides CAN bus or RS485 communication of battery status ‘state of charge’ and alarms etc. It may also be used without CAN bus interface with just basic analog inputs and outputs for simpler systems.

GTCAP uses only CAN or RS485 open protocol. We can support customers in interfacing & adapting to different protocols they are using.

Each module is programmed with individual ID number e.g. 001 and the BMS can address directly with each module on a shared communication channel.