Why is my battery not charging to 100%?

We occasionally get the question:
• Why is my battery not charging to 100%? Or
• Why is my battery State of Charge (SoC) dropping by a few perent each day?
NOTE: The answer below applies to AM2s and X101s. (The voltages will be different for AM5s,
Blades, etc, ...).

For an AM2 or X101:

• The battery must be charged up to 53.6 V.
• For the State of Charge (SoC) to reset to 100%, the battery voltage must be above 53.3 V and
the charge current must have tapered off to be less than ~2 Amps.
For inverters that are connected to the BMS’s CANbus (e.g. Sunsynks), the BMS (or Cloudlink) will
instruct the inverter to charge to 53.6 V. (On a Sunsynk, you can confirm this value under the Li-BMS
menu.)
Sometimes the inverter will be measuring 53.6 V on its DC terminals but the final voltage on the
battery will be ~0.4 V lower, i.e. 53.2 V. In this case the SoC will not reset to 100%.
A suitably qualified person, can use a proper digital multimeter to confirm the voltage at the
inverter’s DC terminals. If the inverter calibration is out, then there a few ways to solve the problem:
• contact the inverter’s tech support and fix the inverter calibration;
• install a Hubble Cloudlink, it will automatically increase the Charge Voltage Limit sent out by
the CAN to compensate for the inverter’s calibration error;
• update the firmware on the BMS to v4.5 (or higher) which will lower the BMS calibration
threshold to accommodate for up to a 0.5 V error on the inverter calibration; or
• put the inverter in voltage control mode (i.e. lead battery mode) and set the Charge Voltage
Limit to 54 V.
o We use 54 V here to allow for a small voltage difference in what the inverter
measures and the battery measures