Sparrow / NmG
On my two Sparrows I have installed small smart float chargers, one on each individual battery, which I engage after most of the Zivan's bulk charging:
The charge profile seems to me to pretty well match the Optima's needs.
Minor mods to these chargers: On the battery-side I shortened the wire and added ring terminals for attaching directly to the battery clamps. On the ac side I greatly shortened the wire and added black/white Anderson connectors, allowing me to daisy-chain and snake a single 120vac wire with Anderson connectors in both battery compartments, ending in a single two-prong 120vac plug under the hood. Current draw is quite low, combining to just a little over one amp ac at max charge rate. Secure this charger to the top of each battery with Velcro™
I built a little ac shutoff box which monitors a single battery voltage and turns off the Zivan when that battery gets to 15.0v (room temp). I have a PakTrakr (calibrated) so I know which individual battery in the string usually gets to 15v first and use that most- susceptible battery to trigger the shutdown.
Thus my procedure is to bulk charge using the Zivan through a mechanical timer for added safety (I can now very well judge when the pack will be full, approximately one hour at 120vac for every seven miles driven on level ground) and through this shutoff box. What's great is that I simply activate the small chargers after the Zivan's bulk charging and leave everything alone, with each individual charger in effect balancing its own battery. I typically keep the small chargers active for about a 6-8hours (they have a little light that turns from red to green when float kicks in - so it's important to install each charger so that light is visible), and in recent months I've been getting lazy and plugging these in at the same time I turn on the Zivan (which is immediately after any driving) with these float chargers continuing after the Zivan shuts down. I leave the front hood open and car seat ajar when charging, but I've never had good batteries even get more than slightly warm when charging.
Here's a photo of the battery compartment which shows the spaghetti mess of not just these float chargers but the PakTrakr wiring and its modules and the overvoltage shunts (Hot Juice Electric BEQ-1 15.6v that came with this blue Sparrow when I bought it).
A couple of weeks ago in the Blue Sparrow I had to replace one of the worst-located batteries in the front (#8), but replaced #9 at the same time and simplified things a little by taking out the BEQ-1 shunts in the front compartment since I never drive any of the Optimas that high.
Been doing this for about three years, with the orange Sparrow accumulating around 6000 miles on one set of batteries so far (that I had totally replaced) and they're still happy, whereas I keep replacing individual batteries in the blue Sparrow as they die (about one or two a year) - they were a mixture of old and new when I bought it. One or the other Sparrow continues to be used daily, despite the addition of an i-MiEV to the stable.
The photo below is of my orange Sparrow without the Zivan and shows the small chargers as well as my individual battery access for monitoring and individual charging if required: Anderson connectors fed from each battery through a 30A fuse.