Hello,Mr Taz,
1). Use a well-regulated constant-voltage power supply that puts out 12.9V to 13.1V as a "float charger". Such a supply should by design be "current-limited" to between 0.5A to 2A, so that if connected to a mostly discharged battery, it doesn't catch fireYou can build your own with an AC powered wall-wart that puts out ~15V DC, followed by an IC regulator like an LM317. Such a "float charger" can be left connected 24-7. I get five years or more of service from float-charged batteries.
A long-term "float-charged" battery will benefit from a once-per-month "equalization charge", for which you need a separate constant-current supply (I use a lab supply which has built-in electronic current limiting). Google "equalization charge".
I have got a Float charger for sealed lead acid batteries for 2Amp. This is for 12v and 6v. And it has a trimmer for adjusting the correct voltage. Can you tell me which is the correct charging voltage for 6v open lead acid batteries?
Thank you,