battery advice

[Maccatak]

Hi fella's
the battery that was in my boat when I purchased it has just packed it in, it is a century ns70, cca 500, rc 110. When I went to replace it the bloke told me i should get a marine version as it has a deep cycle or something which I did. The thing I am not sure about is when not in use how often do you charge them? Can you over charge them? I have a 4amp charger which i usually put on the night before a trip,but it is mainly inbetween trips i am concerned about.
Thanks for any help
Grant.

[littlejim]

Macca,

I started off charging my battery like you with a 6 amp 'automatic' charger. Put it on a soon as I put the boat back in the garage and turned it off when I went back home to canberra. Despite this the battery gradually went down to 'poor' on the hydrometer readings.
Round about this time some of the members on one of the boards, who had worked in battery manufacturing, told us about 'smart' chargers'. These switch to what they called a 'floating' charge once the battery is fully charged and don't boil off the water/electrolyte like the other chargers do.
I bought one of these 'smart' chargers at Altronics for about $35, Dick Smith and Tandy have them too. Mine only puts out about 0.75 amps, so it's no good for overnight charging if the battery is low, but I leave it on all the time I'm in canberra, sometimes up to a month, with no problems.
The 'poor' battery reading came back up to 'good' once I left it on the 'smart' charger and the battery is still going strong 18 months later. I think it's about 4 yrs old now too.

At first I was worried that the water would still boil off, so I watched it over about a week and couldn't see any bubbling. When I did the same with the 6 amp 'automatic' you could see the water breaking down. (it doesn't really boil, it breaks down into hydrogen and oxygen, or it used to in those physics experiments at school many years ago.)

[Maccatak]

Thanks heaps littlejim,
I'll invest in one of those chargers tomorrow.

All the best
Grant