I was wondering what current flow people are seeing when float charging their packs.
I recently build a charging/maintaining station similar to the one Zaine described. But, instead of eight batteries I only have four; two good batteries and two pretty worn out practice batteries. As Zaine described, connecting a pair of uncharged optima batteries to a pair of charged optima batteries is not a problem. The internal resistance is high enough that there is no damaging current flow.
One unexpected thing is the relative current flow while float charging. The Redtop spec sheet recommends float charging at a voltage between 13.2 and 13.8 volts. At this time I am float charging at 13.2 volts. Interestingly, this results in a pretty steady current flow between .1 and .2 amps for my four battery setup which equals between .025 and .05 amps per battery. The current flow is the same if the pack has been float charging for 1 hour of 72 hours.
I've never checked what the float current is with a meter. With the Iota charger I've got, I've left the plug out when the batteries are not being used as a float charger. It most likely is down around the lower end of less than one full amp I would guess. Unless I got a separate CA meter on it with a shunt, then I could track to see how much is going into the batteries along with how many watts are going back in as well for recharging after a race. I've kept the plug out on it since both chargers are at 13.6 volts, with the plug in it jumps to 14.2 volts.