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Types of deep cycle batteries differ in how they hold their electrolyte and how much care they need, and the right type turns on where the battery lives and how it charges. A flooded battery needs water and ventilation, a sealed battery needs neither, and a lithium battery needs a charger made for its chemistry. This guide walks through each type, from the flooded lead acid cell to the lithium pack, so you can match the battery to the job before you buy.
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The quick answer: types of deep cycle batteries
A deep cycle battery is built to discharge deeply and recharge, over and over, where a starting battery only gives a short burst. Flooded lead acid is the oldest shape and the lowest-cost one, but it needs water top-ups and ventilation. Sealed lead acid and AGM cost more and need no water, gel is sealed too but fussy about charging, and lithium costs the most while lasting the longest and weighing the least. The rest of this guide takes each type in turn.
Flooded lead acid
Flooded lead acid is the classic deep cycle battery: liquid electrolyte in open cells, with caps you remove to top up the water. It suits golf carts, utility vehicles and floor machines, and it tolerates deep discharges when it is cared for. The U.S. Battery in this guide is a flooded set of 4, a 12V 155Ah deep cycle GC12 battery, listed at 122 Ah at the 5-hour rate and 155 Ah at the 20-hour rate, with 292 minutes at 25 amps and 77 minutes at 75 amps, at 86.0 pounds and a 12 month manufacturer warranty. Flooded batteries need ventilation and regular water checks, so they suit a ventilated compartment, not a sealed box.
Sealed lead acid and AGM
Sealed lead acid, or SLA, holds the electrolyte so it cannot spill, and AGM takes that further with the acid held in a glass mat. The result is a battery that needs no water, can sit in more positions, and still gives a deep cycle. The Mighty Max in this guide is a 12V 35Ah SLA battery, maintenance free and spill proof, at 7.5 by 7.75 by 5.0 inches, listed as a replacement for 33Ah, 34Ah and 36Ah batteries. It is listed with a high discharge rate, a wide temperature range, a long service life and deep discharge recovery, and it suits solar setups, trolling motors, mobility chairs and small inverters.
Gel batteries
Gel batteries are sealed lead acid with the electrolyte turned to a gel, so nothing can spill and the battery needs no water. They charge slowly and dislike overcharging, so they need a charger with a gel setting and a steady hand on the voltage. They suit the same jobs as AGM, such as wheelchairs, solar storage and marine use, where the battery may sit for long stretches between charges.
Lithium (LiFePO4)
Lithium iron phosphate, or LiFePO4, is the newest deep cycle type in common use. It weighs far less than a lead acid battery of the same size, holds its voltage steady as it discharges, and lasts through far more cycles. It needs a charger made for lithium chemistry and a battery management system to guard the cells, and it costs more up front than any lead acid type. See LiFePO4 battery life for how long these batteries last.
| Type | Electrolyte | Care needed |
|---|---|---|
| Flooded lead acid | Liquid acid in open cells | Water top-ups and ventilation |
| Sealed lead acid | Sealed, spill proof | No water, little care |
| AGM | Acid held in a glass mat | No water, little care |
| Gel | Gelled electrolyte, sealed | Needs a gel charger setting |
| Lithium LiFePO4 | Lithium cells with a BMS | Needs a lithium charger |
How to choose the best type
Match the type to the job first, then to the size. A golf cart or a floor machine that lives in a ventilated bay suits flooded lead acid, while a solar setup in a cabin suits sealed AGM or lithium. Check the amp-hour figure at the rate that matches your load: the U.S. Battery here lists 122 Ah at the 5-hour rate and 155 Ah at the 20-hour rate, so the same battery reads differently at different draws. Check the group size, the weight and the warranty, and check the charger before you buy, since each chemistry needs its own charging profile. See what voltage a deep cycle battery should be when the bank voltage is still open.
FAQ: power away from the grid
What is a deep cycle battery?
A battery built to discharge deeply and recharge, over and over. It suits solar storage, RVs, golf carts, trolling motors and mobility chairs, where the load draws power for hours at a time.
What is the difference between flooded and AGM batteries?
Flooded batteries hold liquid acid in open cells and need water top-ups and ventilation. AGM batteries hold the acid in a glass mat, are sealed and spill proof, and need no water. The Mighty Max in this guide is a sealed 12V 35Ah AGM battery, maintenance free at 7.5 by 7.75 by 5.0 inches.
How many amp-hours does a setup need?
It turns on the load and the hours it runs. Check the amp-hour rate that matches your draw: the U.S. Battery here lists 122 Ah at the 5-hour rate and 155 Ah at the 20-hour rate, with 292 minutes at 25 amps and 77 minutes at 75 amps.
Can a flooded battery be replaced with a lithium battery?
Yes, when the size fits and the charger suits lithium chemistry. A lithium battery needs a charger made for LiFePO4 and a battery management system, so check the charger before you swap the battery.
How long does a deep cycle battery last?
It turns on the type and the care it gets. Flooded batteries last longest with regular water checks, AGM and gel last with gentle charging, and lithium lasts the longest of all. The Mighty Max listing claims a long service life and deep discharge recovery, and the U.S. Battery carries a 12 month manufacturer warranty.
Related solar guides
See every Batteries and Charging guide, plus the deep cycle and RV batteries, the LiFePO4 vs lead-acid battery for RV and LiFePO4 battery life.
