Deep Cycle Ignorance

Yep - the wisdom I've collected says keep the battery fully charged at all times - my CT has an inbuilt charger - I just connect the mains and switch it on, once a month when the CT is not in use. The voltmeter in the CT indicates about 14v+ when full, on charge, then settles back to 13.6 or so at rest. Re the charger type - I'll leave that to the forumnal experts that will pop up soon - the "smarter" the charger though, the better it seems..... knows when to go back to a trickle, after having given the battery a good blast.

I agree that you should fully charge the battery before storing and if possible leave it connected to a "smart" multistage charger. I use a CTEK 7A unit which cost about $300.00 and which are distributed is OZ by Bainbridge Technlogies QLD.
There has been lots and lots of discussion about the pro and cons of different types of batteries, but my personal experience is that I have not been able to fully charge my deep cycle wet cell battery (AGM are different) using the tow vehicle's standard alternator/voltage regulator no matter how long I'm on the road.
When using the mains CTEK 7A charger it gets to about 80% overnight but can take another 48 hours or so before it switches to maintenance mode and is fully charged.
Check out this web site:
http://www.uuhome.de/william.darden/index.htm
or this one:
http://www.windsun.com/Batteries/Battery_FAQ.htm

Regards,

Brad,

If you don't mind keeping an eye on things, the cheapest way is just a basic 4 amp battery charger and a cheap digital multimeter. The battery should only need charging every month if there are no parasitic loads from things like radios etc. If the no load terminal voltage drops below 12.6 volts it indicates that the battery is at about 80% charge and that it is time to top up again. Charge at a moderate current (a 4A charger does this anyway) until the terminal voltage is about 14.4 volts.

Another thing to remember is that deep cycle batteries take a very long time to charge at the regulated voltage from a normal vehicle alternator which these days is about 14.2 volt. With the voltage drop which is inevitable from the alternator to your C/T battery it is unlikely that any significant discharge of the C/T battery will be replaced during a normal day's driving. Using your handy digital multimeter will help monitor this.

Phil I

Brad, for a budget system that works go to Kmart and buy the following two items:

http://www.projecta.com.au/products/index.php/command/viewproduct/productserial/20/categoryserial/10

http://www.projecta.com.au/products/index.php/command/viewproduct/productserial/81/categoryserial/6

Connect them together so as the power goes from the battery charger to the regulator and leave them connected permanently to the Deep Cycle battery.
Cost about $160 total.

For a more refined system use a conventional three stage battery charger rated at about 10% of the A/H ( 10amp charger for 100A/H battery ) of the battery system minium, as the trickle charge system will not allow the full charge to cook the battery/s.

Brad like the others have said, automatic chargers are the best way to go heaps of choices and price ranges though, check out these three stage fully automatic chargers, 6 amp $99.00 or 10amp for $159.00 at http://www.absorbedpower.com/battery/products/
Also Projector have some automatic low amp maintanance chargers that others on here have found at Bunnings/Kmart on special sometimes.
Cheers.