Charging a Deep Cycle Battery from Cigarette Lighter Socket

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Charging a Deep Cycle Battery from Cigarette Lighter Socket

Deep Cycle Battery

Deep cycle batteries are mainly used for marine vehicles, golf carts, traffic lights, etc. Designed to release less charge than a standard battery over a longer period of time, they have thicker plates than regular vehicle batteries which provide a strong charge base.

Deep cycle batteries come in various forms that are manufactured to perform different functions:

  • Flooded Wet Cell Battery: These are also known as sealed batteries that contain electrolyte fluid and have plates that are submerged in the chemical solution. They are considered low maintenance batteries because of their dual alloy or hybrid plates composed of lead and calcium. The level of electrolyte should be above the plate, working as a reservoir and ensuring that the slightest decrease in the water level does not affect the chemical composition of the battery.

The capacity of these batteries is dependent on the electrolyte level and its depletion can reduce the life expectancy rate. Thus it is advisable to check the level at regular intervals and test the electrolyte capacity with a hydrometer to prevent damage.

  • Absorbed Glass Mat Battery (AGM): The type of deep cycle battery where the electrolyte is immersed in a fiberglass mat. The plates in these batteries are flat and wet or sometimes bound in a tight spiral composed of lead and acid. They are also called starved electrolytes because the fiberglass mat is 95% saturated with sulphuric acid, leaving no excess fluid in the battery.

It is considered that the internal resistance of AGM batteries is poor when compared to any traditional battery; they acquire slower resistance when it comes to sustaining high temperatures and controlling self-discharging. Thus, they have to be well maintained and kept in a cool and compact location. But as they are totally sealed and not composed of fluid, AGM batteries can be easily transported without worrying about leakage and spillage.

  • Gel Battery: These are another form of deep cycle battery that contains some of the features from both flooded and AGM batteries. Its electrolyte composition is in a semi-fluid state made up of silica, causing it to stiffen up more than a flooded battery. Gel batteries are usually sealed but some are valve regulated, in which case tiny valves sustain a positive pressure in the battery.

Gel batteries are considered the most sensitive of deep cycle batteries due to their adverse reaction to over-voltage charging. The greatest advantage of gel batteries is that they have high resistance power and can be used in extreme temperatures for a longer period. If gel batteries are used with unsuitable chargers, it can result in premature failure and/or insufficient power supply. 

Over Charging Deep Cycle batteries

Excessive supply of charge above the desired range of capacity will create decomposition of the fluid level, which results in premature aging. When a high amount of charge is pushed into the battery, it will progressively heat up. This phenomenon is called thermal runaway which will destroy the battery within hours of overcharging.

Undercharging Deep Cycle Batteries

Just like overcharging, undercharging can also result in damage to the battery over time. If less voltage is supplied to the battery, the current flow will eventually stop prior to the complete charge. This allows lead sulfate to settle on the electrodes reducing the capacity of the battery. This entire process is called sulfating which causes premature failure and reduction in the ampere capacity of the battery.

Storing Deep Cycle Batteries

Never store a deep cycle battery in a discharged state; this can develop a layer of lead sulfate on the electrodes and make it difficult to charge again. Preserve the battery in a cool and dry place with proper ventilation and recharge it at regular intervals.

Amp-Hour Capacity of Deep Cycle Batteries

The capacity of deep cycle batteries is measured in amp-hours which is determined by multiplying the amp rating of the battery with the hours of charging. 

Example: If you have a battery with 20 amps rating and it takes 20 minutes to charge completely, then the amp hours of your battery will be 20 amps x 0.333 hours = 6.67 AH. 

Charging a Deep Cycle Battery 

Appropriate charging can provide sustainable life to your battery, but improper charging can reduce its lifespan. There are several charging methods that are used in different situations.

Charging with Battery Charger

The traditional method to charge a deep cycle battery is with a battery charger.

Charging your battery with Cigarette Lighter Socket

Using your vehicle’s cigarette lighter socket to charge your deep cycle battery can be considered an emergency measure for a battery that might need charging between journeys. Before attempting this, make sure that the cigarette socket appliance is protected by a 15 amp fuse. The voltage must be kept as low as possible so that it does not blow the fuse connected to the lighter socket.

All you have to do is connect your deep cycle battery with the cigarette socket in your vehicle, preferably using a heavy gauge copper cable. The car’s circuitry must have the lighter socket “live”. It may require setting the ignition switch to “accessories.” Remember to keep the charge rate sufficiently low enough not to blow the fuse associated with the lighter socket (often 10 Amps).

Note: The charging duration should not exceed one hour; detach the cables before the socket heats up and causes further damage.

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Steve Brown


Steve is a gadget enthusiast who's always been intrigued by batteries. The founder and editor of Battery Chargers Info, he's assembled a group of like-minded experts to cover every facet of portable power His aim is to help you learn more about your favorite gadgets and their batteries so you can maximize both their performance and their life.

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