First, the question must be answered as to why someone might consider installing a battery that is physically larger and of a different type than that specified for their vehicle. The answer is to increase total available current and battery longevity. If you install a larger starting battery, you will end up with more Cold Cranking Amps and more Reserve Capacity than you would get with a smaller battery of similar quality. If you install a larger Starting/Deep Cycle or Deep Cycle battery, you will get a very durable battery with a much higher RC and about the same or perhaps somewhat fewer CCAs. The battery will also probably last longer as deep cycle batteries have thicker plates with more active material.
There are also reasons not to do this that should be considered: [ol][*]Starting/Deep Cycle and 12 volt Deep Cycle batteries do not come with as long of a warranty as do high quality starting batteries. This should NOT be taken as an indicator of reduced longevity in an automotive application however, as these batteries are normally subjected to very deep cycling in their intended application, which is very hard on any lead-acid battery. Also, these batteries are often subjected to long periods of storage without charging, which leads to sulfation. In automotive use batteries are seldom cycled deeply, so they should actually last longer in most cases than a starting battery, provided that you add distilled water as needed.[*]Starting/deep cycle or deep cycle batteries require periodic watering with distilled water. If you want to avoid having to add water, either forget going with a deep cycle or get one of the new spiral plate, sealed AGM starting/deep cycle batteries like an Optima Blue Top.[*]You are not mechanically inclined or don't like working on your car. If this is you, forget it and go with the specified size in a sealed, maintenance free battery. In order to install a large battery, you will likely have to perform some modifications to the mounting hardware. You must ensure that the hood does not contact the positive battery post, even when it is dropped or slammed shut, not only to prevent any possibility of shorting, but to prevent denting of the hood as well. You must also make sure the battery does not shift or vibrate excessively.[/ol]
If you decide to do this, be sure to select a 12 volt battery (6 cells). I know that everyone should know this, but thought I had to mention it. Also, get the smallest size you can find (size 24), with a height of no more than 8” (not including caps or posts). Finally, select a battery that is made to handle a certain amount of shock and vibration, like a marine/RV battery. Do not get a battery intended for a stationary application, like renewable energy storage.
I will document the installation of a size 24 starting/deep cycle battery in another post later today. [align=left] [/align]

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