When to Charge the Battery

Opportunity charging is OK. Charging the battery after every use will not reduce its life.
Partial State-of-Charge is OK. If the battery SOC is greater than 10% at the end of discharge, it does not require an immediate charge. However, do not continually leave the battery in a partial state of charge as that will reduce its performance as battery cells will become unbalanced.
Every 4 cycles, fully charge the battery so the inverter-charger reaches the charge termination criteria. This ensures the battery cells are balanced and that each battery cell is fully charged.
Charge if below 10% SOC. If the battery has been discharged below 10% SOC, it must be charged within 24 hours to avoid permanent damage to the battery. Otherwise, irreversible damage to the battery cells will occur in a very short period of time.
Low charge current extends life. Charging at 50% of nominal current or lower helps extend the battery cycle life.
Charge within the proper temperature range. Ensure that charging is within the charge temperatures specified in Environmental Specifications.

NOTICE

BATTERY DAMAGE

The battery must be charged within 24 hours if discharged below 10% SOC. Otherwise, irreversible damage to the battery cells will occur in a very short period of time and void the warranty.
Do not continually leave the battery in a partial state of charge as that will unbalance the battery cells. Fully charge the battery every 4 cycles so each battery cell is fully charged. If the end of charge criteria is not regularly performed, multiple balancing charges may be required to fully charge each battery cell.
The following are two ways to perform a balancing charge.
- Reduce charge termination to 100 mA and maintain 55.2 V for 10 hours.
- Charge in a closed-loop configuration.

Failure to follow these instructions may result in equipment damage.

NOTE
When the HELIOS ESS battery cells are between -25°C (-13°F) and 5°C (41°F) and either connected to a charging source or SOC is 50% or more, energy is diverted to the internal heater until the battery cells reach 8°C (46.4°F). If the BMS triggered the Under-temperature in Charge protection, the battery will not allow charging until the cell temperature is 4°C (39.2°F).