AGM Deep Cycle Batteries (Absorbed Glass Mat Deep Cycle Batteries) and Conventional Car Batteries may both be lead acid batteries or rely on the same electrochemical reaction but the jobs they are designed to perform are vastly different. If you try to use a deep cycle battery to start your car or putt a conventional car battery in your caravan you can damage your equipment, not to mention it being highly unsafe.
To help you better understand the workings of deep cycle batteries and conventional car batteries, here’s our guide to the main differences between the two. You can also take a look at our blog post on marine starting batteries VS deep cycle batteries.
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Thanks to a thin sheet of Boron-Sillicate glass mat sealing in electrolyte between thick lead plates, deep cycle batteries are able to provide a low to medium current over an extended period of time. While the car battery provides a surge to start your car, the AGM deep cycle battery is not designed to be used as a cranking battery as the draw needed to start up is too high to be sustained. Continuously using an AGM deep cycle battery in a cranking situation with a high draw out of the battery will cause damage and may shorten your battery’s lifespan. Typically AGM deep cycle battery’s have a sensitivity to heat that makes them unsuited for use under the bonnet of a vehicle, however in some instances you may be able to bypass this with the use of a heat shield or specific engine configuration. Always best to speak to an expert regarding your Deep Cycle Battery Setup.
In an AGM Battery the glass mat stops the electrolyte from being free-flowing, reducing the risk of spillage if the batteries are placed on their side and eliminating the problem of gassing. This makes deep cycle batteries ideal for use in confined spaces, such as caravans or boats, unlike the conventional car battery.
Deep Cycle Batteries are built with thick lead plates, which helps them withstand the repeated charging and discharging as they are used for cycling purposes. As a general rule of thumb, the heavier the deep cycle battery, the thicker the lead plates, the longer it will last.
A car battery is designed to provide the strong surge of current needed to turn the engine over during starting. Once this burst of current has been provided, the alternator takes over to provide all the power the car needs, meaning the battery itself will not need to be drained much lower than twenty percent of its total capacity. This contrasts with the deep cycle battery’s ability to be deeply discharged over and over again. Conventional car batteries are built with thinner lead plates compared to deep cycle batteries, and this is one of the main reasons they will not last as long when used in a cycling scenario.
Cold Cranking Amps are the unit used to measure the number of amps produced by the battery at zero degrees 0oF/-18oC for 30 seconds. The conventional car battery has a much higher CCA rating than the deep cycle battery as it needs to produce a short sharp burst of energy to start the vehicle’s engine. The deep cycle battery on the other hand has a CCA rating of around half the conventional car battery but is able to withstand many more charge and discharge cycles.
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