Deep Cycle Batteries

What is a Deep Cycle Battery?

battery business, marine battery

Let's clear up the difference between deep cycle batteries and cranking batteries.

When you need a lot of power quickly to start your car or run a really powerful winch, you need a cranking battery.

Cranking batteries can't cope with being deeply discharged. Leave your car lights on and get a flat battery and it will never fully recover.

Deep cycle batteries are designed to have lots more power drained from them. They don't get damaged by deep discharge and are ideal for running things like lights, autopilots, fridges and fans.

Think of a cranking battery like a sprinter and a deep cycle battery like a marathon runner.

And yes... the man propping up the bar who tells you deep cycle and cranking batteries are the same... is blowing smoke.

At Battery Business we spend 7 days a week recommending and installing deep cycle battery systems.

Most people find the best way to make a smart choice is to call us on 02 9970 6999 and get some advice from one of our technical team.

We stock Lion and Rocket, Trojan, Fullriver, Lifeline, Optima, Duracell, Sonnenschein, Drypower, amongst others, and we have access to many other brands of deep cycle batteries - you can be sure whatever your battery needs - we have the solution.

OK. Let's talk about the different types of deep cycle battery.

Accessible Low-Maintenance

battery business, golf cart battery

Accessible low-maintenance deep cycle batteries are ideal when the batteries are worked really hard and then electrolyte needs to be topped up.

So for example we supply the local golf courses with this kind of battery for their buggies.

If your golf cart is flat we'll the check the charger and battery free of charge and give you a solution. There is no point replacing the battery if a faulty charger is just going to damage the new battery.

Compared to the equivalent cranking battery, conventional deep cycle batteries have thicker plates and a denser Lead/Antimony paste formula. This makes them more robust so they cope with more discharge cycles.

Some of the high quality accessible batteries also have a different electrolyte structure to make them last much longer.


Sealed Maintenance Free

battery business, marine battery

Sealed maintenance free deep cycle batteries are a modern option to low-maintenance batteries. They are built with more fluid cover over the plates, so as they gas off moisture throughout their life, it takes longer for the electrolyte to get below the top of the plates but, when it does, the battery is scrap - simple as that.

There is a huge range of quality among these batteries. The very best ones will give you many years of service if you charge them correctly. There are also 4 levels of deep cycle battery ranging from very occasional use (often referred to as standby), occasional to regular use (often referred to as limited cyclic), regualr use (typically the minimum level for a deep cycle battery for camping or marine use) and EV rated for electric vehicle applications, where the charge and discharge regime is brutal.

You can only use any of the above batteries where there is sufficient ventilation - like for example under a bonnet or in an engine room - not under the seats of caravans or inside cars or boat cabins where people breath the air that the battery vents into.

If you're not sure what kind of battery you need, or what is safe to use, call us on 02 9970 6999 and get some advice from one of our technical team.

Absorbed Glass Mat (AGM)

Absorbed Glass Mat (AGM) deep cycle batteries have a similar construction to the ones above but with glass matting built between the plates. This matting absorbs the acid and swells to fill the gap between the plates.

This gives better conductivity, improved vibration resistance and, therefore, potentially longer battery life.

AGM batteries are a premium product at a premium price. Expect to pay 25-50% over maintenance free batteries for the equivalent power.

In most cases though, the improved performance and greater longevity will mean the cost per day is lower over the life of the battery.

These batteries are almost gas free so you can use them where there is very little breathing space or when they are in the same airspace as people. Because they don't spill we often use them in racing yachts where the boat can heel at quite an angle for long periods of time. In fact, many racing rulebooks insist upon the use of AGM or Gel batteries in the vessels that are racing.

AGM batteries can also be designed to have high cranking power as well as coping with deep discharge so you can choose these where you need blend of cranking and deep cycling. More about AGM batteries here

Recently we were called to a 50+ foot motor yacht on Pittwater. It had a mix of battery types, so most of them were receiving the wrong charge profile, it had cranking batteries in deep cycle locations, and low-maintenance batteries that were impossible for anyone of adult proportions to get to and to maintain. The result was a multi-million dollar boat that the owner could not trust to start when he needed it to, or to run the onboard systems (or even the fridges).

battery business

One battery bank had failed entirely (one bad battery dragged the rest down), another bank had swelling batteries, and one battery had gassed off and eventually exploded, sending acid for several feet in every direction.

We arranged for the mess to be cleaned up, replaced a total of 20 batteries with the right choices throughout, adjusted the chargers (which takes about 10 minutes in most cases) and we now have an owner that can enjoy their boat to the full.

Gel Batteries - Gelled Electrolyte

Gel deep cycle batteries are similar to AGM except for that the electrolyte is in a jelly form instead of soaked into a glass mat.

Once the gel sets during construction the battery is a solid block of lead and firm jelly giving excellent conductivity and extremely high vibration resistance.

These are typically used for frequent and deep cycling. They usually cost around 10% more than equivalent AGM battery (construction is a little more expensive) but in the same sized case will give the ability to be cycled more deeply and, in some case, have a design life of a decade or more.

Lithium Batteries

battery business

Lithium deep cycle batteries are one of the cutting edges of accessible battery technology (there's always something new around the corner). There's weirder stuff going on in laboratories, but lithium is where it is at in terms of retail product, for now.

They use very expensive technology and offer a very flat power band from fully charged to almost fully discharged. Realistically a lithium battery can deliver more usable power out of the same size case, together with a weight saving of around 60%, and more cycles before the battery is ready for recycling.

Lithium batteries are fast charging, sealed maintenance free and often controlled by highly advanced electric battery management units (BMUs).

The advantage to you is many, many more cycles before your battery is exhausted, improved power to weight, faster charging, longevity, clean power...

...the weight savings are huge - for example we might take several-hundred kilos off a boat when we replace conventional batteries with lithium...

...but at a price. Lithiums cost a lot more, and must be installed by people with the right experience and knowledge, using the right chargers, and with the right switches and safety mechanisms in place. Used correctly, lithium batteries are exceptional, and the performance can be well worth the investment. Like most things, though, a little knowledge is a dangerous thing, and you get what you pay for.

If you're not sure what kind of battery you need call us on 02 9970 6999 and get some advice from one of our technical team.