Lithium-ion batteries have the advantage over traditional lead acid in that they can be cycled many times more and can be discharged deeper while maintaining a decent battery life.
For those not overly familiar with electrical power, this system can store around 5 Units of electricity in the batteries.
This means that at during a power failure, you could watch a 200W TV for about 25 hours before the batteries went flat (200W x 25 hours = 5000Whrs = 5 Units of electricity)
