On Fri, 23 Dec 2011 09:57:53 +1300, Gib Bogle
wrote:

Mine is a crude basic one, and I fear that I may have caused damage on
occasion.

Well, if you know you're laying the battery up for a while, you can
still utilise a basic charger - just have it timed to come on for
30mins/day or for a longer period limit the charging current to half
an amp or so. I found a headlamp filament is a readily available
resistor.
I've been using both of these techniques for years before I bought
some Lidl chargers and the batteries survived well enough.