emergency lighting conversion
Since White LEDs typically run at 3.2V, one could use two low Vce(sat) NPN's from Diodes Inc. and make a CC sink using Ie=20 to 30mA x27 @.65V using Re=0.65 Ohm or whatever matches 1A sink and Rb= 33xRe to give the best results with above assumptions. Power rating of Re must be rated >=1W.

CC design is common knowledge and repeated on this site.

For those new to CC sink solutions.   for review, the base resistor can be used to enable or pulled up to Vin biases the collector to saturate must have IB=10% of IC but for 'diode inc" HYPERBARRIER PN diodes parts 2 or 3%  Ib is minimum but more will reduce  Vce(sat) better than any other Silicon parts.   

Treat this design as a 2 pin design on Vcc side is a current source, or on ground side as a current sink. Either way works.  Any parts work with > 2V drop @1A, Diodes Inc parts can achieve down to 1V drop at low battery.

A more efficient design might use LIPO 4V cells with a fixed resistor  rather than 6V Lead acid. to drive 3.2V LEDs.