Maintenance Free Deep Cycle Battery Types

Deep cycle batteries are designed for cyclic applications like trolling motors and RV comforts. These batteries use thicker lead plates to provide power for longer periods of time.

They can be maintained by adding water to their individual cells or through periodic float equalization. There are several construction types: flooded, gel and sealed AGM.


Unlike starting batteries, deep cycle batteries are designed to produce power sustained over long periods of time and to be discharged deeply (80-100% DOD). They also have thicker plates than starting batteries. The energy capacity of a deep cycle battery is rated in amp-hours, which is one amp for an hour or 10 amps for 1/10 of an hour. It is generally accepted that a battery will last 20 hours at this rate of use.

Sealed batteries are a good choice for RE applications that require a large amount of storage energy. They are a great alternative to flooded lead-acid batteries, maintenance free deep cycle battery which require regular maintenance and produce harmful gases when overcharged.

The electrolyte inside unsealed or flooded batteries is in liquid form, but in sealed batteries, the electrolyte is either in gel (GEL) or is replaced by an acid-soaked glass mat that is sealed between battery electrodes (AGM). This makes sealed batteries non-spillable, low self-discharge, easy to transport and can be used in any position.

These batteries are a bit more expensive than FLA and have a shorter life than FLA. However, they are a great option for solar electric and backup power systems because of their high efficiency, deep cycling capability and durability. They can be connected in series or parallel to create DC voltage as needed, and can be charged with a smart charger.


A flooded deep cycle battery has a liquid electrolyte that can be opened and refilled with distilled water. These are the traditional engine starting, tractor, and golf cart batteries. They must be refilled periodically to replace the lost water that happens during recharging and normal use. It is important to add only distilled water to avoid any impurities that could damage the battery’s internal components. Adding too much water will also reduce the battery’s capacity. Ideally, the battery should be filled to 1/8″ below the maximum water level indicator.

It is common for flooded lead acid batteries to have an amp-hour (AH) rating that indicates the total amount of current the battery will deliver for one hour. This number can help you compare the AH capability of different deep cycle batteries that are similarly sized.

While it is possible to use a flooded battery for deep cycle applications, most of the time a sealed battery will provide better performance. The main advantage of sealed batteries is that they are free from fumes, Hydrogen, and leakage. They are also resistant to freezes.

If you are interested in a maintenance free deep cycle battery that does not require any recharging, Gel or AGM batteries would be a good option for you. While they are more expensive than standard flooded batteries, these types of batteries are designed to last for years without any significant loss in battery capacity.


Deep cycle gel batteries are a maintenance free option that can be used in a variety of applications. They contain silica that freezes the electrolyte in the battery into a gel, making it non-spillable and easy to maintain. These batteries are also better able to handle temperatures and don’t require as much ventilation.

They have a slower chemical reaction than flooded and AGM batteries, so they are more resistant to sulfation and can be charged at lower voltages. These batteries also hold their power longer than flooded or AGM, and can be fully discharged without losing their performance.

Gel batteries are a great choice for applications that need long bursts of energy, as they will provide consistent power over extended periods. These batteries are also safe to use in cold weather and can withstand shocks and vibrations. However, the major drawback of gel batteries is that they take longer to charge than flooded or AGM batteries. It is important to monitor them during the charging process and remove them as soon as they are fully charged, as leaving a battery on a charger for too long can cause irreversible damage. The price tag on these batteries is more expensive than flooded or AGM, but they are worth the investment for their versatility and longevity. You can find these batteries in a variety of sizes, so you’ll be able to find the perfect one for your application.


Although not technically maintenance free, AGM (absorbent glass mat) deep cycle batteries are becoming more popular because of their superior performance over standard flooded lead acid (SLA) battery technology. These batteries use a fiberglass mat that absorbs the electrolyte and makes it non-spillable. This mat also optimizes the plate surface area for better electrolyte distribution over traditional batteries. This improves battery performance and lifespan over SLA types.

While AGM batteries can be used in a Gel battery variety of applications, they are best suited for those who need a maintenance free deep cycle battery that can withstand high temperatures. Extreme heat can damage battery cells and cause water loss, which reduces capacity. Cold temperatures can also reduce battery life and performance.

AGM batteries are valve regulated, meaning they have a small safety valve that keeps a slight positive pressure on the inside of the battery case. This prevents water loss even if the battery is tipped over or damaged. However, if the battery is over charged or undercharged, this will damage the batteries and may result in permanent failure.

It’s important to check the voltage of a deep cycle battery often to avoid damage and premature failure. You can do this by using a digital voltmeter or taking a hydrometer reading (refer to the battery brochure for more information). Never remove the caps on a sealed AGM or gel cell battery because you will contaminate the internals and void any warranties.