care of Deep Cycle Batteries

Have a bit of a read here.

Battery Info

John,

The Wind&sun site shown by Notso is an excellent reference for battery and battery charging information. At the bottom of the web page is a coloured graph, showing the Green, yellow and red levels of a battery's state of charge voltage.

In short though, yes, you can certainly overcharge a battery if using a "dumb" charger that just pumps a constant voltage and current into it.
The maximum volts for a battery is approximately 12.8v (fully charged) and should be measured without a charger operating at the time.
The "minumum" voltage is 10.4v (dead flat)
A deep cycle battery can survive a reasonable drain on it's capacity (up to 70% drained) but just a few cycles of full drainage of a battery can render it "buggered" due to plate sulfation.

The best investment you can make is a muli-stage charger to look after your battery.
A multi-stage charger goes through several steps to supply a good charging regime, ending up with a maintenance charge mode that ensures the battery has reached 100% capacity and will not be overcharged. The charger can be left on for prolonged periods without damaging your battery.

Another good investment for remotely mounted batteries such as that in your caravan, is the ability to charge it while travelling from your vehicle alternator.
To give the best possible charging process for this method and overcome voltage drop from a long cable run, a dc-dc charger which is also includes a multi-stage process is the best solution. Some models also include the ability to add solar panel input when stationary, in situations where you are camping away from 240v sources.