Why lithium-iron-phosphate?

Victron Energy Lithium Battery Smart batteries are Lithium Iron Phosphate (LiFePO4) batteries and are available in 12.8V or 25.6V in various capacities. They can be connected in series, parallel and series/parallel so that a battery bank can be built for system voltages of 12V, 24V* or 48V*. The maximum number of batteries in one system is 20, which results in a maximum energy storage of 84kWh in a 12V system and up to 102kWh in a 24V and 48V system.

A single LFP cell has a nominal voltage of 3.2V. A 12.8 V battery consists of 4 cells connected in series and a 25.6 V battery consists of 8 cells connected in series.

Rugged

A lead-acid battery will fail prematurely due to sulfation:

• If it operates in deficit mode during long periods of time (i.e. if the battery is rarely, or never at all, fully charged).
• If it is left partially charged or worse, fully discharged (yacht or mobile home during wintertime).

An LFP battery:

• Does not need to be fully charged. Service life even slightly improves in case of partial charge instead of a fullcharge. This is a major advantage of LFP compared to lead-acid.
• Other advantages are the wide operating temperature range, excellent cycling performance, low internal resistance and high efficiency (see below).LFP is therefore the chemistry of choice for demanding applications.Efficient

• In several applications (especially off-grid solar and/or wind), energy efficiency can be of crucial importance.
• The round-trip energy efficiency (discharge from 100 % to 0 % and back to 100 % charged) of the average lead-acid battery is 80 %.
• The round-trip energy efficiency of a LFP battery is 92 %.
• The charge process of lead-acid batteries becomes particularly inefficient when the 80 % state of charge has been reached, resulting in efficiencies of 50 % or even less in solar systems where several days of reserve energy is required (battery operating in 70 % to 100 % charged state).
• In contrast, a LFP battery will still achieve 90 % efficiency under shallow discharge conditions.

Size and weight

• Saves up to 70 % in space
• Saves up to 70 % in weight

Expensive?

• LFP batteries are expensive when compared to lead-acid. But in demanding applications, the high initial cost will be more than compensated by longer service life, superior reliability and excellent efficiency.

Bluetooth

• With Bluetooth cell voltages, temperature and alarm status can be monitored.
• Instant readout: The VictronConnect App can display the most important data on the Device list page without the need to connect to the product.
• Very useful to localise a (potential) problem, such as cell imbalance.

*To reduce required balancing time, we recommend to use a little different batteries in series as possible for the application. 24 V systems are best built using 24 V batteries. And 48 V systems are best built using two 24 V batteries in series. While the alternative, four 12 V batteries in series, will work, it will require more periodic balancing time.