This paper presents experimental investigations into a hybrid energy storage system comprising directly parallel connected lead-acid and lithium batteries.
The combination of these two types of batteries into a hybrid storage leads to a significant reduction of phenomena unfavorable for lead–acid battery and lower the cost of the storage compared to lithium-ion batteries.
What is hybrid energy storage?
Hybrid energy storage, that combines two types of batteries, can be made with direct connection between them, forming one DC-bus, nevertheless such a connection eliminates possibility of an active energy management and power distribution between batteries, what is necessary to reduce lead–acid battery degradation.
In authors proposed plug-in module, consisting of lithium-ion battery and supercapacitor, that is connected to the lead–acid battery energy storage via bidirectional DC/DC converters. The aim of the module is to reduce current stress of lead–acid battery, and as a result to enhance its lifetime.
Why are lead-acid batteries so popular?
Lead–acid batteries are popular mainly because of low cost and high reliability , what makes them attractive, especially in the developing countries. However, they feature short life-cycle and are not resistant to conditions that may appear in PV systems like undercharging, low state of charge (SoC), high charging current .
Are lithium-ion batteries a good alternative?
Therefore lithium-ion batteries are usually proposed as an alternative, nevertheless, due to the higher cost, they are used mostly in developed countries, where PV system operates in on-grid mode, and battery is used for the purpose of an energy balancing, .
Among many technologies that allows for storing energy, electrochemical batteries are most popular in residential PV installations. Lead–acid batteries are popular mainly because of low cost and high reliability, what makes them attractive, especially in the developing countries.