A lead-acid battery is a storage battery used with battery inverters such as the Sunny Island, where it is selected as either flooded (FLA) or valve-regulated (VRLA) type instead of lithium-ion. A flooded lead-acid battery has a liquid electrolyte, while a VRLA battery has its electrolyte immobilized either in a gel or in an absorbent glass mat (AGM). The electrolyte is water mixed with sulfuric acid, and charging always produces hydrogen and oxygen gas. In sealed types this gas recombines into water inside the battery, so they rarely need topping up with water. AGM batteries usually handle high currents well but hold up poorly to repeated deep discharge, while some gel batteries are built to tolerate very deep discharge cycling. Flooded batteries need periodic watering at the interval the manufacturer specifies. If the battery sits at a low state of charge for a long time, sulfation sets in. It can be reversed only by periodic full charges, and once it crystallizes it permanently cuts capacity and can crack the battery jar. The inverter's battery management handles careful charging, deep discharge prevention and state-of-charge estimation, but its parameters must be set to the battery manufacturer's recommendations. Spent lead-acid batteries have a well-established recycling industry, because lead is toxic and regulated and the batteries are used widely in other industries.
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related_toc1 verified · fact Lithium-ion battery
SMA battery inverters offer lead-acid (FLA, VRLA) or lithium-ion as alternative battery type settings.
tbl=84.r6 h=c6683e875c06tbl=85 h=7520405a2919tbl=87.r3 h=bcd98df7f444tbl=45 h=5e488f822451verified by: review-workflowverified on: 2026-10-24
c2 verified · fact Nickel-cadmium battery
Listed alongside FLA and VRLA as a selectable battery type.
tbl=40 h=daa5da0df125tbl=158.r25 h=ebcc391e8d61verified by: review-workflowverified on: 2026-10-24
c3 verified · fact Sunny Island 4.4M / 6.0H / 8.0H
Supports FLA and VRLA lead-acid batteries with integrated battery management.
verified by: review-workflowverified on: 2026-10-24
c4 verified · fact Sunny Home Manager proposed
Offers optimized discharge of lead-acid batteries using load profile and PV yield forecast.
tbl=15.r1 h=133e20e3743averified by: review-workflowverified on: 2026-10-24
c5 drafted · lead State of charge
Extended low state of charge causes sulfation; deep discharge area for lead-acid is defined separately from lithium-ion.
sec=h154 h=bbb8a4584c8esec=h8 h=8e08e205856etbl=45 h=5e488f822451c6 drafted · lead Battery charging stages
Charging parameters must be matched to the manufacturer's recommendations; charge regulation voltage differs by lead-acid type.
sec=h8 h=8e08e205856esec=7.6.2 h=bcc826ed8451tbl=7.r2 h=0cfbb82f90bcc7 drafted · lead Battery sulfation proposed
Crystallized sulfation permanently reduces capacity and efficiency and can swell or break the battery jar.
sec=h154 h=bbb8a4584c8ec8 drafted · lead Vented battery gas
Hydrogen and oxygen are generated whenever lead-acid batteries are charged.
sec=h641 h=869a64288abasec=h617 h=8784572c2a3dc9 drafted · lead Battery electrolyte exposure
Electrolyte is a mixture of water and sulfuric acid.
sec=h641 h=869a64288abasec=h617 h=8784572c2a3dc10 drafted · lead Battery watering proposed
Watering applies to flooded lead-acid batteries only, at manufacturer intervals.
tbl=33.r11 h=7ad1c3db5aa5related_to c7related_to c2related_to c4related_to c3related_to c1related_to c8related_to c5related_to c6