What is a deep cycle battery?

What is a deep cycle battery
What is a deep cycle battery

In case you’re looking for a battery for solar and renewable Energy or a battery for camping – nine times out of ten you’re looking for a Deep Cycle Battery. Deep cycle batteries are extremely efficient energy storage Units. They work when a chemical reaction occurs that develops a voltage which Results in electricity. Deep Cycle Batteries are designed to be ‘cycled’ (discharged and recharged) several times over, so while some car battery aims to send A burst of energy for a brief time, a deep cycle battery gives power in a Steady speed for a protracted period.


What are the Different Kinds of Deep Cycle Batteries?

The most typical Deep Cycle Batteries are Gel Batteries and AGM Deep Cycle Batteries (Absorbed Glass Mat); and in more recent times lithium-ion and Carbon Lead. Browse deep Cycle battery sorts in our online store.


AGM Batteries – Deep Cycle Battery Types

AGM Batteries - Deep Cycle Battery Types
AGM Batteries – Deep Cycle Battery Types


Absorbent Glass Mat (AGM) is a type of lead-acid deep Cycle battery in which the electrolyte is absorbed to some fiberglass mat. You will find the plates within an AGM battery are flat like wet cell lead-acid batteries, or they might be wrapped into a tight spiral. The internal resistance of AGM batteries is lower than conventional cells; they can handle higher temperatures and self-discharge more gradually which other kinds of batteries.

AGM batteries have a discharge valve which will be activated after the battery has been recharged at large voltage. This valve activation enables a small amount of active substance to escape, and this reduces the overall capacity of this battery. AGM batteries typically have gasoline diffusers built into them which allow for the safe dispersal of any excess hydrogen that is created during charging. The principal advantages of AGM Batteries and the reason for their popularity is that they are classed as batteries. Unlike routine lead-acid batteries which should be kept in an upright position preventing acid spills and thus ensuring the discs are sitting at the electrolyte; AGM Deep Cycle Batteries can be put in any orientation.


The Advantages of AGM Deep Cycle Batteries


  • They Are totally sealed and are easy and safe to transfer
  • They never need topping up with water
  • They May be safely mounted within a boat, car, caravan, motor home, or some other Recreational motor vehicle.
  • AGM Deep Cycle Batteries just need to be vented to atmosphere, unlike other outside like wet batteries, and could be mounted on either side or ends if required.


Due to their very low Inner resistance AGM batteries May Fully charge in a lower voltage, and take a much larger load charge current. Meaning that when charging from a standard car/truck alternator, these Batteries may be fully charged, in around three hours! AGM batteries are also discharged ‘deeper’ than conventional deep cycle batteries with no major damage. For example, AGM Batteries just self-discharge at the speed of up to 3 percent Cared for, they can be recharged and put into full service without any major damage. AGM batteries were originally developed for the army; they are very powerful.


Organizing Your Deep Cycle Battery

Reputable performance and long service life depend upon correct charging. Faulty procedures or inadequate charging equipment result in diminished battery life and/or unsatisfactory performance. The choice of appropriate charging circuits and methods is equally as important as picking the perfect battery for your program.

To obtain maximum service life and capacity, along with Acceptable recharge period and economy, continuous voltage-current limited charging is advised.

During charge, the lead sulfate of the positive plate Becomes carbon dioxide. As the battery reaches full charge, the positive plate starts generating dioxide resulting in a sudden rise in voltage because of decreasing internal resistance. A constant voltage charge, therefore, allows detection of this voltage increase and so control of the present cost amount.


Overcharging Deep Cycle Batteries

As a result of too high of a charge voltage excessive current will flow in the battery, after reaching full control, resulting in decomposition of water from the electrolyte and premature aging.

At high levels of overcharge a battery will progressively heat up. As it gets hotter, it will take more present, heating up even further. This is called thermal runaway and it may destroy a battery in as little as a few hours.


Undercharging Deep Cycle Batteries

If too low a fee voltage is applied, the flow will essentially stop before the battery is fully charged. This allows a number of the lead sulfate to remain on the electrodes, which will gradually reduce capacity.


Batteries That Are stored in a discharge condition, or left The shelf for too long, may initially appear to be “open circuited” or will Accept much less current than normal. While this occurs, leave the charger connected to the battery. Usually, the battery will start to accept increasing amounts of present until a Normal present level is attained. If there is no answer, even to charge Voltages above recommended amounts, the battery may have been at a discharged State for too long to recover.


Do’s & Don’ts for proper use of your Deep Cycle Batteries

Alternators & Generators what you need to know about



Generally speaking vehicle or van Alternators work reasonably well with AGM batteries. They are not battery chargers however, and will never fully charge a Deep Cycle Battery, therefore it’s ideal to use a battery charger when main power is available to top up the battery charge and prevent reduced battery life out of sulphation.

Notice that alternator output voltages are usually reduced by Cable/wiring runs and Dual Battery systems so care needs to be taken to measure the actual voltage obtained in the battery across its terminals to make sure it’s adequate to control the battery completely.

Conversely for Gel batteries fitted close to the alternator (under-bonnet with a thick gauge cabling) there’s a real risk of damage due to Over-charging since the alternator output could be too high for the battery. It is for this reason that we highly recommend NOT using GEL batteries automobile alternators.




Many Mobile Generators do not have battery charging circuitry built-in and must be used with care if they supply a DC outlet (although you could plug a battery charger into the 240V socket, it seems a fairly inefficient way to operate).

The subsequent models (from Honda et al) using the built in Where they’re permitted (or if off-site), although some users do grow tired of the noise and migrate to solar as time passes.

Capacity & Resistance in Deep Cycle Batteries

Amp-Hour Capacity

An amp-hour is one amp for one Hour or 10 amps for 1/10 of an hour and so forth. It’s amps x hours. If you have something which pulls 20 amps, and you also use it for 20 minutes, then the generally accepted AH rating time frame for batteries for nearly all deep cycle Batteries is the “20 hour rate”. A 10Hr rating is Popular in the United States, Therefore many batteries can have 10hr, 20hr or two specifications said. The 20hr rating means It Is discharged down to 10.5 volts over a 20 hour Period while the entire actual amp-hours it supplies is quantified. Occasionally Ratings at the 6 hour rate and 100 hour speed are also given for comparison and for different programs. The 6-hour rate is often used for industrial Batteries, because that is a typical daily duty cycle. Occasionally the 100 hour rate Is given just to create the battery seem better than it really is, but it is also Useful for figuring battery capacity for long term applications such as backup.


Internal Resistance

Part — or most — of the reduction in discharging and charging batteries is because of internal resistance. This is converted into heat, and that’s why batteries get hot when being charged up. The lower the internal resistance, the greater battery life. AGM batteries have resistance levels upto 5 times lower than regular batteries.

A Battery rated at 180 amp-hours more than 6 hours might be rated at 220 AH at the 20-hour pace, and 250 AH at the 48-hour rate. Much of the loss of efficacy is due to higher internal resistance at higher amperage rates — internal resistance is not a constant — kind of like “the more you push, the more it pushes back”.

Typical performance in a lead-acid battery is 85-95%, in Alkaline and NiCad battery it’s about 65%. 98%.


Why AGM Deep Cycle Batteries are popular?


AGM [Absorbed Glass Mat] VRLA

AGM [Absorbed Glass Mat] VRLA
AGM [Absorbed Glass Mat] VRLA
Sealed Absorbed Glass Mat (Ca/Ca) VRLA deep cycle batteries (also known as “starved electrolyte” or “dry”) possess a very nice fiber Boron-Silicate glass mat Between their horizontal Lead with Calcium alloy in the positive and Lead with Calcium metal in the negative plates. The AGM battery was invented in 1980 and first utilized in military aircraft in 1985.


AGM, or Absorbed Glass Mat Batteries

A newer kind of sealed battery utilizes “Absorbed Glass Mats”, or AGM involving the plates. This is a really fine fiber Boron-Silicate glass mat. These Kind of Batteries have the benefits of gelled, but can take a lot more abuse. These can also be called “starved electrolyte”, as the mat is about 95% saturated Rather than fully soaked. That also means that they won’t leak acid even if broken.


Lifespan of Deep Cycle Batteries

With how it is used, how it’s maintained and charged temperature, and other aspects. Gelled cells batteries can be destroyed in 1 day when compared using a large automotive charger. Golf cart batteries can be destroyed without being used in less than a year because they were left sitting in a hot garage without being billed. Even the so-called “dry charged” (in which you include acid when you need them) have a shelf life of 18 months in the least. They are not totally dry — they are actually full of acid, the plates charged, then the acid is dumped out.

These are some typical (minimal — maximum) typical expectations for batteries should use in deep cycle service. There are so many Variables, such as thickness of release, upkeep, temperature, how frequently and How deep cycled, etc. that it’s almost impossible to give a fixed number. But here goes anyhow:

  • Starting: 3-12 months
  • Marine: 1-6 years
  • Golf cart: 2-7 years
  • AGM deep cycle: 4-10 years
  • Gelled deep cycle: 2-7 years
  • Telephone (float): 2-10 years. These are usually special purpose “float service”, but often appear on the surplus market as “deep cycle”. They can vary considerably, depending on age, usage, care, and type.
  • NiFe (alkaline): 5-35 years
  • NiCad: 1-20 years


Deep Cycle Battery’s Inverters

An inverter has basically two functions — to provide an Alternating current (ac) voltage as opposed to the direct current (dc) accessible in the battery, and also to increase the voltage up to a mean of 240V. There are several kinds of inverters. The most expensive provide a pure sine wave that’s favored for any sensitive equipment, especially notebooks. The cheapest only provide a square wave ac, which is satisfactory with most motors and some small chargers for cameras, phones, but not for many laptop computers. There are also intermediate kinds, “modified sine wave”, which combine a number of square waves to approximate a sine wave form. These are normally satisfactory for notebooks, but, like the square wave kinds, often create a lot of wireless interference.


Managing Deep Cycle Batteries

  • Always wear insulated gloves when handling batteries; particularly when connecting series and parallel groups of batteries.
  • If equipment is to be saved for a long period of time that the Batteries should be disconnected to avoid undue drain on the batteries as well as any potential for damage to the equipment.
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