Check into one of these Soneil trickle chargers. they are available in either 36 or 48 volt. You can just disconnect the main leads to the cart and leave the whole pack tied together. It will charge all the batteries together at once. It is a fully automatic charger, you can leave it on indefinetly. I would then hook this up to a timer and have it come on for maybe 4 hours every other day. Have someone stop by periodacally and check the water levels. This should keep your pack "fresh".
http://soneil.com/36_volt.html
http://soneil.com/48_volt.html
http://www.batterystuff.com/battery-...SON3616SR.html
http://www.batterystuff.com/battery-...on4808SRF.html