This is great. I now have the green light to add another 6v battery to my setup.
The problem is I already have a transformer set up which charges my present batteries at about 3 amps and trails off to less than 100ma when the batteries are fully charged. I would have to set up another charger as I prefer to charge all the batteries at once and at the same charge rate.
I do agree with you that the bike is much nicer to drive with that bit of extra power.