Fleet battery maintenance and charging

Anyone here have recommendations for real deal battery recovery and maintenance tools?  I have about 12 infrequently used cars, and several are not at my residence, so popping out to start them up is an infrequent occurrence. 

I have Battery Tender Jr.s on six of them, and have still arrived to find the battery deceased and the tender blinking green and red.  This may be due to extended power outages at the storage building, but I'm not there and can't tell when these happen.  By the time the batteries are that far gone, a portable jump pack just sees them as a dead short (sits there and beeps sadly) or can't provide enough juice to start the car unless the battery is removed from the system.  As I don't like firing up the car and shutting it off again before it's all come up to operating temps, I'm not a big fan of running off the jump pack for that long.

Is a big, ignorant brute force jump starter(12/40/200 Amp monsters with wheels) the best bet, and if so, which ones have people had good experiences with?

I have had decent luck with the uber cheap hammer store float chargers but only on standard lead acid batteries.  Believe the last couple bought were $203 each.  I have a solid battery tender unit I keep the dry cell rabbit battery on.

I hear you on the battery situation--plus one of my chargers just died as well. (Might have been operator error.)

FWIW, we have a battery charger video that might help.

Thanks for the reply Mr. Wallens.  I think I'm still leaning towards a monster industrial style jump box though.  Shortening the battery lifespan by 5-10 percent doesn't bother me when the things are otherwise dead anyway.  Two of the vehicles are on sealed gel cells, so there's definitely no "topping off the electrolytes"...