When you have a new battery installed or a battery changed under warranty, the inverter needs to perform a process called ‘calibration’ of the battery.
Periodically or if your battery is not storing the energy you think it should, it can be worth doing a battery calibration.
The calibration process is used to determine how much energy the battery can store, and in particular the high (100%) and low (4% reserve) state of charge points. Battery state of charge (SoC) is a measure of how much energy is in your battery, but the battery has no direct way of measuring this. The battery management system can only measure battery voltage, and from that it infers what the SoC is.
The calibration process thus discharges the battery to a low voltage level, measures that level and records internally that this is the 4% level, it then charges the battery until it won’t charge any more, and again records the voltage level as being 100% energy.
Calibration can be initiated from the GivEnergy portal, GivTCP or the BBC basic inverter app. Once the calibration is initiated it shouldn’t be stopped, although you can change the battery charge and discharge rates, e.g. to complete the discharge and charge activities in preferential electricity rates.
The calibration process consists of the following stages:
- Stage 1 – Discharge to 44v
- Stage 2 – Set 0%
- Stage 3 – Charge to 57v
- Stage 4 – Set 100%
- Stage 5 – Balance
- Stage 6 – Write Battery capacity flag Ah
During Stage 1 as the battery gets below 48v it begins throttling
During Stage 4 as the battery gets over 55v or the old 100% voltage level, it is throttled
