Off-grid battery options

ACID-LEAD BATTERIES

Prior to the last three or four years, lead-acid deep cycle battery systems were the most prevalent and dependable alternative for off-grid systems. Lead-acid batteries are an established technology that can endure for at least 15 years if not stored at temperatures over 40 degrees Celsius and provided they are not routinely depleted too deeply. Lead-acid batteries need accurate battery charging in accordance with a predetermined charge cycle and temperature sensors to adjust voltage settings. The majority of well-known off-grid inverter-chargers have configurable charge voltage settings as well as sensors for exact charging in any environment. As shown below, lead-acid deep cycle batteries continue to be used and provide various benefits over lithium.

Options for lead-acid deep cycle batteries – 2V, 6V, and 12V voltages and numerous kinds – Gel, AGM, Submerged

Options for lead-acid deep cycle batteries – 2V, 6V, and 12V voltages and numerous kinds – Gel, AGM, Submerged

In contrast to current lithium batteries, one of the greatest advantages of lead-acid batteries is that the battery will not shut down at a low voltage or state of charge (SOC). This is crucial, particularly in times of emergency or when a backup generator fails. Since a backup option, lead-acid batteries may be depleted to 0% state of charge, however this is not advised as it can drastically diminish the battery’s lifespan.

Advantages:

• Compatible with the majority of inverters.
• Proven and dependable technology
• Totally risk-free (sealed Gel/AGM)
• **The battery will not shut off at low SOC or voltage.
• Longevity (if not over discharged)
• Simple to recycle

Disadvantages:

• 75% to 80% round-trip efficiency.
• Low energy density – Extremely weighty
• Regularly, usable capacity is restricted to no more than 40% of the Department of Defense.
• Not modular – Size is fixed after installation
• Cannot maintain a partial charge for extended durations.
• Temperatures that are too high may severely impact battery life

** Cutoff voltage and SOC are determined by inverter settings and discharge rate.

LITHIUM ION

Due to their excellent round trip efficiency (92% to 98%), small size, low weight, and scalability, lithium-ion battery systems have gained tremendous popularity in recent years. Lead-acid battery banks have a set size or capacity, but lithium systems do not. This scalability allows for the installation of more capacity at a later date, which is a huge benefit for both installers and consumers.

Lithium batteries offer a far better energy density than lead-acid batteries, making them lighter and more compact. A significant benefit of lithium is its capacity to maintain a low state of charge (partial state of charge) for an extended period of time without sulfation, a typical issue with lead-acid batteries. Additionally, lithium may attain extraordinarily high charge rates with charging times up to 70% quicker than lead-acid.

See also our comprehensive solar battery evaluation – a comprehensive comparison of the most recent lithium batteries from the industry’s top manufacturers.

Advantages

• 92% to 98% round-trip efficiency is really high.
• Extremely high energy density – Small and Light
• High charging and discharging rates were enabled
• No concerns with partial condition of charge deterioration
• Scalable and modular systems (upgradable)
• Particularly safe and low-risk (if charged appropriately) are LFP cells.
• The majority of lithium batteries provide a 10-year guarantee.

Disadvantages

• Can shut off if temperatures over 45 degrees Celsius.
• Capable of shutting down at low temperatures (below 5 degC)
• Can “trip” under sustained strong surge loads.
• More challenging to recycle at the end of its life.
• Possibly inoperable without a suitable inverter (CANbus)
• Lithium batteries that operate independently of the power grid

CONTROLLED LITHIUM

Numerous lithium battery systems have a BMS that needs a specific communication connection with the inverter to function. If the inverter and battery are incompatible, they cannot function together and will not operate. A possible difficulty with this sort of technology is that if communication is lost or experiences interference, the inverter or battery will shut down to prevent overcharging or discharging. Numerous managed battery systems include individual module-level monitoring, which is very helpful if one or more modules are underperforming or defective.

The prevalent Pylontech US3000C (LFP) modular rack mount battery system communicates with the inverter through CANbus.

The Pylontech US series and BYD LVL Premium series are popular managed lithium batteries used for grid-connected and off-grid systems because they are compatible with a broad variety of hybrid and off-grid inverters, including as SMA, Selectronic, and Victron. Here is the complete list of lithium battery management choices.

LITHIUM UNDER LITHIUM

There are various lithium battery choices that are self-managed and feature a BMS, but do not need a communication link (such as CANbus) with the inverter to function. Most self-managed batteries are modular and can be grown to produce battery banks with very high capacity (up to 500kWh). Simpliphi, GenZ, Discover AES, and Powerplus Energy are popular brands. Similar to controlled batteries, the BMS monitors the condition of charge, temperature, and cell voltages. Since they do not need additional communications or connections, this sort of battery system may be quickly adapted and utilised to replace current lead-acid battery banks. In the case of a system shutdown or system black owing to a low state of charge or low voltage, the majority of self-managed batteries will resume automatically without requiring human activation or reset.

Best Lithium Off-Grid Batteries

Self-managed lithium batteries are the most dependable option for off-grid systems, based on my own experience and the opinions of other expert off-grid system installers. Managed lithium batteries are also a highly dependable solution, but their reliance on communications, which may become unstable at low charge levels and low temperatures, might be troublesome. Most self-managed lithium battery systems are compatible with almost all off-grid inverters; they are also very flexible, do not need communication lines, and can be upgraded to bigger capacities that are more suitable to off-grid systems. If necessary, more capacity may be added at a later date. Self-managed lithium batteries are compatible with the majority of inverter-chargers and MPPT solar charge controllers and may be used as a drop-in replacement for older lead-acid batteries.

LEAD-ACID BATTERIES

High-performance lead-acid batteries are still a great option for off-grid systems in certain circumstances. Lead-acid is an established and dependable technology that is compatible with the most majority of off-grid inverters and solar charge controllers. At certain cases, lead-acid battery banks may be more trustworthy since the battery does not shut down automatically in severe temperatures or when it reaches a low level of charge. Moreover, they may be recycled simply utilising existing infrastructure.