BFL is not your alternator feeding the batteries on the ride home, so that when you get home they have been recharged to some degree?
Makes senese that your powermaxes then can get them upto 14.7sish with well under 20% of your capacity rating.
Seems like all you need to do is flip the breaker on the alternator feed on the drive home then you can blast them with your adjustable voltage powermaxes high amperage at home.
I'd not freak out about surpassing that 27% max rate your batteries list in PacNW ambient temperatures. Monitor them for excessive heating.
I like seeing just how long my battery can accept high amperage, and compare that time to the next time I decided to do it.