Lithium batteries - are they the right choice for you?

 

NOTE THIS PAGE IS STILL UDER DEVELOPMENT AND NOT FULLY COMPLETED

 

Lithium Iron Phosphate (LiFePO4) batteries deliver high energy and power density for mobile applications.  They have the best combination of performance, safety, cost, reliability and environmental characteristics suitable for high power output applications. 


One of the key benefits of LiFePO4 batteries is the longer life when compared to the current deep cycle lead acid batteries.  They are also lighter in weight which is an important consideration for mobile applications.

The up front cost is higher than AGM but in the long term they prove to be better value for money.

 

Are LiFePO4 batteries safe?

Several chemistries of Lithium such as Lithium-Ion, Lithium Iron Phosphate and Lithium Polymer are available.  The LiFePO4 batteries are the safest type of Lithium batteries as there is no danger of the battery erupting into flames as with Lithium-Ion.  They will not overheat, and they will not catch on fire, even if punctured. 

The other advantage of LiFePO4 batteries is they do not have any negative health risks or environmental risks as the cathode material is not hazardous.

 

LiFePO4 Battery features:

  • Higher energy density than comparable lead acid batteries;
  • Deeper discharge capability of lithium-ion batteries provides more useable capacity than lead acid batteries of the same rated capacity;
  • Increased life (>10 years) than deep cycle lead acid batteries in deep discharge applications;
  • The energy density advantage combined with ability for increased depth of discharge makes LiFePO4 batteries ideal for use in mobile applications;
  • Battery life is directly related to how deep the battery is cycled each time. Lower the discharge rate, longer the battery life. In most applications battery storage is designed for 70-80% depth of discharge to reduce battery weight and acquisition costs;
  • Their voltage remains almost unchanged down to 80% discharged state;
  • There is no memory effect and no scheduled cycling is required to prolong the battery's life;
  • High charging and discharging rates;
  • Can be used as starter battery.
 

Installation

Optimum results are obtained if batteries are installed within 1 metre cable distance of the inverter and 2 metres of cable distance of the solar charge controller.  Battery packs can be installed in any configuration to suit the shape of your installation site.
 
Note: 4 x 3.2 V cells make up a 12 V battery
 

Battery management requirements for using LiFePO4 batteries in caravans and RVs 

Typically, caravans and other RVs tend to be used only part of the year.  The batteries are therefore idle for significant periods.  This cycle of constant use followed by dormant periods requires specific management of the State of Charge (SoC) of the battery otherwise the health and life expectancy of the battery will be reduced.   We have completed extensive research on the most appropriate battery management system (BMS) and now have stock of the REC BMS which meets the specific needs of Lithium batteries.

LiFePO4 batteries require an advanced Active BMS that uses high efficiency bi-directional active balancing to increase the efficiency of the battery charging.  The REC BMS features include cell protection, state of charge, state of health and impedance calculation.

 

REC Active BMS
The advanced 12V BMS by REC has active balancing which transfers charge between cells.  The significant benefit of active balancing is to eliminate the shunt resistors which discharge excess charge as heat and increases the overall efficiency of the charging process.  
 
Key features of the Active BMS:
  • high efficiency 2 Amp bi-directional active balancing (pack to cell and cell to pack);
  • cell voltage monitoring with high and low voltage protection;
  • robust design for vehicular use;
  • IP65 protection enclosure;
  • Automotive grade water resistant connector;
  • 2 – 5 V measuring range, 2 mV accuracy;
  • up to 8 digital temperature sensors;
  • shunt current measurement;
  • galvanically isolated RS-485 and CAN communication protocol;
  • two programmable fused relay output (charge and discharge protection relays);
  • two programmable fused digital output (switching based on operator selected charge state);
  • factory assembled wiring harness;
  • optional touch screen display showing detailed battery parameters, state of health and state of charge;
  • interface modules for control of Victron, Enerdrive, Redarc, etc charging devices (under development).