Deep cycle batteries are designed to be just that - deep cycling. That means charge them, then drain them down to just about flat. A starting battery is just about the opposite - draining it down to flat damages it.

Deep cycle - charge, use completely, charge...
Starter - charge, use moderately, top up, use, top up...

A deep cycle battery will often have enough CCA (cold cranking amps) to start you car, and although a starter battery may have a similar amp-hour rating to a deep cycle, draining it flat by pumping the tunes without the engine running will kill it.

Likewise, if you're pumping the tunes with the engine going, you're better off saving your money on your battery, and upgrading your alternator so it can keep your starting battery fully charged.

The biggest gain of an Optima (red, blue or yellow) is that they have bloody quick charge times compared to most standard batteries. But you still need your alternator to be able to charge the baby up!

If you want the best of both worlds, get a red top to power your amp while you're driving, and flick it over to a yellow if you're cranking volume up with the engine turned off.

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