Keeping your Battery Bealthy
Not so long ago, the early adopters who purchased and installed lithium-ion batteries for off-grid applications could only rely on manufacturers’ specifications for guidance. These batteries were designed for the electric vehicle (EV) market, where charging speed and the ability to deliver high current are paramount. Over time, after extensive testing and many dead battery banks, they learned from their mistakes.
Learn about the optimal conditions and a few simple precautions to keep your lithium-ion battery healthy for long years of service.
Battery manufacturers’ charge and discharge parameters may not be the most appropriate
for the long-term health of your off-grid lithium-ion battery
All agree that manufacturers’ specifications do not apply to off-grid usage, where battery performance over an extended period (10–15 years) is expected. Although the batteries used by early adopters came from different manufacturers, they all point to the same conclusions. Below is a summary of the optimal parameters these users have found:
| Parameter | Value |
| Maximum charge voltage (bulk / absorption) | 3.45 volt/cell (13.8 volt for a 12V battery) |
| Maximum charge current | < 0.3 C (120 A for a 400 Ah battery) |
| End of charge current | 0.03 C (12 A for a 400 Ah battery) |
| Maximum discharge current | < 0.3 C (120 A for a 400 Ah battery) |
| Minimum voltage at which to stop discharge | 3.00 volt/cell (12 volts for a 12 V battery) |
| State of charge range (SOC) | 10% to 90% |
| Ambient temperature range | 15 ° C to 25 ° C |
Over time, any parameter outside these limits will reduce battery life
Other precautions to take:
- Stop charging when the battery is full. If this is not practical, set the “float” voltage to 3.3 volts per cell, or 13.2 volts for a 12V battery).
- Do not keep the battery fully charged over an extended period. When the battery is not in use or in storage, charge it to 50–60% SOC.
- When the battery is not in use for an extended period, charge it to 50–60% SOC and either
- if you do not need energy: disconnect it from all systems – including battery monitor and EMS, or
- if you need energy: keep a solar panel connected and use a EMS that can control the charge to keep the SOC between 40 % and 60 % SOC (like the TAO EMS)
Be wary of Equipment Specifications
A number of charger manufacturers have based their charge parameters on specifications given by battery manufacturers. These may not be the best for your battery.
We recommend purchasing chargers whose charge parameters can be adjusted. TAO EMS can also be used to compensate for chargers that cannot be adjusted.
Never trust the “lithium” option on a battery charger
Verify the parameters to which that setting corresponds
and compare them to the optimal parameters listed above
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